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Ebbinghaus like model for retention of details from experience

Ebbinghaus like model for retention of details from experience


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I've come across the Ebbinghaus Curve (forgetting curve) showing the retention of learned knowledge over time, but I wondered if there was the same kind of model for the retention of details from experiences over time, i.e., how much detail of an event does someone forget as time passes.

One would guess the same kind of curve may have been produced for this but I'm unsure what to look for.


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The Internal Assessment

  • Relevant Theory: The multi-store model of memory
  • Tip 1: Simplify the IV to two conditions to make the inferential statistics easier.
  • Tip 2: To conduct the inferential statistics, you will need two conditions (mean scores) to compare for onedependent variable. You should therefore focus on the primacy orthe recency effect. Choose one (Note: one of them is much better than the other to choose because there are different results in each condition – see the graph above to make your decision).
  • Tip 3: You will need two average scores to compare. You will need to operationally define what the primacy or recency is in your experiment. For example, if you’re doing recency only, is this the last word in the sequence, the last two words, the last quarter, one third, etc. You could base your decision on the graph above.
  • Tip 4: If you decide against using this study for your IA, check out this blog post instead: Key Studies for the IA

Travis Dixon is an IB Psychology teacher, author, workshop leader, examiner and IA moderator.


Ebbinghaus like model for retention of details from experience - Psychology

In 1885, according to this article in Wikipedia,

Hermann Ebbinghaus discovered that memory decays exponentially. The
formula he came up with for modeling forgetting curve was

Where R is memory retention, S is the relative strength of the memory,
and t is time.

I have a couple of questions about this formula.

1. What are the units for S?

This formula is a variation of the standard exponential half-life
decay function

In that formula, h is in the same units as t (time), so I assume that
S is also in the same units as t (time).

2. What are the units for R?

In the half-life formula, y and y0 are usually mass units (grams).
Since there is no R0, I am assuming that it is "1".

This means that R goes from 1 to 0, which suggests that it's a
probability. Is it the probability of recall?

Note that this formula is only a qualitative approximation to the decay
of memories. It provides little (if any) insight to the mechanism by
which memories may 'decay' and I doubt that
a) it is applicable over a wide range of t,
b) matches statistical data more than very approximately at best.

Also, it is a little self-fulfilling as there appears to be no way to
independantly estimate S other than by recording the R returned by
fitting the equation to some specific set of data. What I am saying here
is that while t is clearly 'time', and R is clearly some statistical
measure of how much 'memory is retained' after time t, it is not clear
that S represents 'strength of memory' in any real sense of the meaning
of S. Might be better to call S the 'memory decay constant' or 'memory
half-life'.

The probability of recall would be a reasonable guess, but without
access to Ebbinghaus' data it wouild be impossible to say for sure.

While I'm no expert, it is my impression that the formula is a fairly
good approximation, at least after new material has been learned.
Ebbinghaus did his research using nonsense words, but I believe others
have extended that to more general data.

There are those who disagree.

If you click on the first reference in the wiki article - you get a 1913
translation of Ebbinghaus' work. There should be enough information
there to answer your questions.

Well, maybe for someone with better statistics skills. One problem
is that most of the charts are poorly labeled or completely unlabeled.
It was often not clear to be what the independent and dependant
variables were.

Finally, the formula above attrobuted to Ebbinghaus is not in this
paper at all!

In Section 29: Discussion of results, the discussion seems to focus on
a binary recall/norecall (what I think he calls "production"). I am
assuming that the actual measure is the point at which the memory
slips below the recall strength.

In short, I believe that R *is* recall probabiity. If you disagree,
please point me to the relevant section of the paper.

I had a closer look at the paper and believe that the error could be in
the wikipedia article. The table just above the heading 'Section 29', in
chapter 7 appears to summarise his data - note that I haven't checked
that it is a valid summary but, assuming it is, it predicts a very
different behaviour from the wiki article.

= exp(-t/s),
whereas a simple fit to the data suggests
b) R

= Ao*t^(-b)
for appropriately chosen Ro,s,Ao,b, over a significant range of t (and
Ebberhaus comes to a similar conclusion about 20 lines down from the
table).

The two behaviours are very different.
a) claims that for any set of learned data, if (for example) you forget
10% on the first day, then you will forget 10% of what is left on the
second day, 10% of what is still left on the third day, another 10% on
the fourth day, etc.
b) claims that for the same set of data, if (for example) you forget
10% on the first day, you might forget another 10% of the total in the
next 2 days, another 10% of the total in the next 4 days, 10% in the
next 8 days, etc..

My guess is that someone, either the writer of the qwiki or the
reference they used to write it, misunderstood or misinterpreted the
papoer and data, or didnt really understand the nature of exponentials
and logarithms. Note that if formula b) is approximately correct then it
is also approximately true that exp(R)

= k*t (for some constant k), so
there _is_ an exponential relationship between memory and time, but just
not of the nature shown by the wiki.

As a physicist (and I have to admit I have no background in psychology
or teh theory of brain function), I always like to check a proposed
formula by looking at what it suggests in real life. If you look at the
comment near the bottom of the wiki that states "In a typical schoolbook
application (e.g. learning word pairs), most students remember only 10%
after 3?6 days (depending on the material)", the (presumably incorrect
?) wiki formula suggests that on the same test the students would only
remember 1% in 6-12 days, and 0.1% in 9-18 days, which might be a little
far-fetched. Whereas formula b) (Ebberhaus' and mine from fitting the
data) might suggest that teh 1% retention might be after 30-60 days (for
example) and the 0.1% retention after a year or two - this 'feels' a bit
more reasonable when compared with my personal experience.

= exp(-t/s),
whereas a simple fit to the data suggests
b) R

= Ao*t^(-b)
for appropriately chosen Ro,s,Ao,b, over a significant range of t (and
Ebberhaus comes to a similar conclusion about 20 lines down from the
table).
The two behaviours are very different.
a) claims that for any set of learned data, if (for example) you forget
10% on the first day, then you will forget 10% of what is left on the
second day, 10% of what is still left on the third day, another 10% on
the fourth day, etc.
b) claims that for the same set of data, if (for example) you forget
10% on the first day, you might forget another 10% of the total in the
next 2 days, another 10% of the total in the next 4 days, 10% in the
next 8 days, etc..
My guess is that someone, either the writer of the qwiki or the
reference they used to write it, misunderstood or misinterpreted the
papoer and data, or didnt really understand the nature of exponentials
and logarithms. Note that if formula b) is approximately correct then it
is also approximately true that exp(R)

= k*t (for some constant k), so
there _is_ an exponential relationship between memory and time, but just
not of the nature shown by the wiki.

What you say makes intuitive sense. Thanks for taking the time to
check it out.

Do you have any interest is doing some consulting on this and related
topics? I have some work I need to do and my math skills are not up to
the task.

= exp(-t/s),
whereas a simple fit to the data suggests
b) R

= Ao*t^(-b)
for appropriately chosen Ro,s,Ao,b, over a significant range of t (and
Ebberhaus comes to a similar conclusion about 20 lines down from the
table).
The two behaviours are very different.
a) claims that for any set of learned data, if (for example) you forget
10% on the first day, then you will forget 10% of what is left on the
second day, 10% of what is still left on the third day, another 10% on
the fourth day, etc.
b) claims that for the same set of data, if (for example) you forget
10% on the first day, you might forget another 10% of the total in the
next 2 days, another 10% of the total in the next 4 days, 10% in the
next 8 days, etc..
My guess is that someone, either the writer of the qwiki or the
reference they used to write it, misunderstood or misinterpreted the
papoer and data, or didnt really understand the nature of exponentials
and logarithms. Note that if formula b) is approximately correct then it
is also approximately true that exp(R)

= k*t (for some constant k), so
there _is_ an exponential relationship between memory and time, but just
not of the nature shown by the wiki.

Glad to have been of help.

Could be interested if there is some small compensation for my time. You
could contact me privately by deleting the 'nospam' (and one of the '.')
from my e-mail address.


Psychology Question Bank &ndash 832 MCQs on "Forgetting" – Part 6

506. A contrasting model of memory reveals that incoming information can be worked on at different levels of analysis the deeper the analysis goes, the better the memory. What is the name of this model?

507. In addition to its transient equality, short- term memory (STM) also has a very limited storage capacity. This storage capacity is estimated to be about:

(a) Five items, plus or minus two (5 ± 2)

(b) Seven items, plus or minus two (7 ±2)

(c) Three items, plus or minus two (3 ± 2)

(d) Four items, plus or minus two (4 ± 2)

508. The storage capacity of short-term memory can be increased by a process known as:

509. The degreet to which incoming information is processed, so that it can be tied to, or integrated with, existing memories, is known as:

510. The partial and altered representations of what is in the world around us is known as:

511. Very often, a profound memory problem with no loss of consciousness is found. It comes on suddenly without any obvious cause and it typically lasts for only a few hours or days before memory becomes normal again. Fortunately, most people who experience such amnesia have it only once. This type of amnesia is called:

(c) Transient Global Amnesia

512. Sometimes people forget their names, where they have come from, who their spouses are and many other details of their past lives. This type of amnesia is called:

(d) Transient Global Amnesia

513. Medical Science reveals that heavy drinking over a period of years, however, can result, through vitamin-B deficits and other chemical imbalances, in irreversible brain damage and a pattern of symptoms known as the :

(c) Transient Global Amnesia

514. Alcohol-induced amnesia is an example of:

515. Very often, aged people suffer from deficits in many intellectual activities i.e. memory, attention, judgement and abstract thought etc. This problem is popularly known as:

(d) Transient Global Amnesia

516. The more concrete and meaningful are the materials:

(a) The greater is its associative value

(c) The difficulty level increases to its maximum

(d) The threshold of remembering increases

517. Through which sense modality, learning leads to more efficiency?

(c) Both Tactual and Olfactory

518. The course of retention which is presented by a curve is called:

(c) Normal Probability Curve (NPC)

519. If the amount of retention is plotted in a graph, then the curve will be a/an:

520. If the amount of forgetting is plotted in a graph, then the curve will be a/an:

521. Most curves of retention for nonsense syllables measured by relearning and saving method commonly agree in showing a:

(a) Positively accelerated form

(b) Negatively accelerated form

522. Studies indicated that the percentage of saving also varies with variation with material. Retention curve for meaningful material may run at a different height from those of nonsense syllables. But, by and large, different retention curves have:

(a) More or less similar characteristics

(b) More or less dissimilar characteristics

(c) Different types of accelerated form

(d) Haphazard accelerated form

523. The main characteristic of forgetting is that, at first, forgetting is rapid, but as time lap­ses:

(a) Rate of forgetting becomes more faster

(b) Rate of forgetting becomes slower and slower

(c) Rate of forgetting comes to zero

(d) Forgetting becomes haphazard

524. The quantitative study of memory presented in the curve of retention or forgetting is the most important contribution of:

525. Retention curve suggests that:

(a) Forgetting is never complete

(c) In the true sense, forgetting never occurs

(d) Memory cannot be measured quantitatively

526. The retention curve obtained by Ebbinghaus suggests that forgetting is most rapid for:

527. According to Gestalt Psychologists, one of the causes of forgetting is low tension in:

528. According to Guilford, recognition means:

(c) Extra Sensory Perception (ESP)

529. Recognition is the most easiest method of testing:

530. Who said that the essential difference between recall and recognition is that in the first case, the stimulus is not there for one’s identification while it is there in the second case?

531. Maximum retention is possible by:

(c) Relearning and saving method

532. Recognition is easier than recall because:

(a) The object is present and mixed with some other new materials

(b) The object is forgotten temporarily

(c) The object bears no resemblance with others

(d) It is predetermined before birth

534. Who said “As similarity between inter­polated activity and original learning is reduced to a near identity, retention falls to a minimum and then rises again but with decrease in similarity it never reaches the level obtained with maximum similarity”?

535. The relearning or Saving method was originally introduced by:

537. You learn something and try to find out much you have retained after a week by trying to learn it again. What is this method of testing retention called?

538. Suppose “S” has taken six trials for Original Learning (OL) and two trials for relearning (RL) what will be his saving score?

539. Forgetting refers to the negative aspect or opposite of:

540. From his experiments on memory, Ebbinghaus had concluded that any material with an associative value:

(b) Has no effect on memory

(d) Sometimes increases and sometimes decreases forgetting

541. Who said that when learning is rapid, forgetting is slow and when learning is slow, forgetting is rapid?

542. Who said that intraserial inferences also lead to forgetting?

543. Who confirmed that forgetting is not so much a matter of decay of old impressions and associations as it is a matter of inhi­bition interference and obliteration of the old by the new”?

544. The first systematic investigation of retroactive inhibition was carried out by:

(a) Muller and Pilzecker (1900)

(b) Bertlett and Santrock (1979)

(c) Anderson and Anderson (1983)

(d) Peterson and Peterson (1959)

545. Similarity and dissimilarity between original learning and interpolated activity has been subjected to a good number of investi­gations, it being a major cause of:

546. Similarity of materials between original learning and retention interval leads to:

547. Who said that incomplete tasks are better remembered than the complete ones?

548. In 15 minute retention interval, if the interpolated activity is introduced between the 6th and 10th minute, retroactive inhibition will be:

549. Many studies on memory indicated that as the interpolated activity continues for a longer period and interpolated learning is done throughly, there is:

(d) Either zero or less forgetting

550. When the Original Learning (OL) and Interpolated Learning (IL) are learnt through the same sense modality than through different sense modalities, inhibition is:

551. A good number of experimenters have opined that the longer the rest and between Original Learning and subsequent recall:

(a) The less is the interference

(b) The more is the interference

(d) Interference is either maximum or zero

552. Forgetting also occurs when new learning is disturbed by the old learning. This is known as forgetting due to:

553. Over short intervals of time, say a few hours, forgetting produced by retroactive Inhibition is:

(a) Greater than proactive inhibition

(b) Less than proactive inhibition

(c) Equal with proactive inhibition

554. A continuous increase in skill after practice ceases is called:

555. Reminiscence particularly occurs in case of:

556. The problem of reminiscence was first studied by:

557. Nonsense syllables, trigrams and verbatims are difficult to remember and hence:

(c) Are not easily forgotten

(d) Are not subjects to amnesia

558. Mc Clelland has found that reminiscene was greater with:

(a) Less rapid presentation

(c) More rapid presentation

559. Long-term-memory (LTM) is otherwise known as:

560. Elaborate rehearsal is more effective for:

561. The most significant feature of short-term memory (STM) is its:

562. “Theory of Disuse” was advanced by:

563. “Theory of Disuse” holds that forgetting takes place as memory becomes fainter due to disuse:

(a) With the passage of time

(b) With the ignorance of “S”

(c) With the ignorance of “F’

(d) With the carelessness of “E”

564. The “Interference Theory of Forgetting” has a:

(b) Behaviouristic Orientation

(c) Psychoanalytic Orientation

(d) Structuralistic Orientation

(e) Functionalistic Orientation

565. Who has concluded that the degree of retroactive inhibition depends upon generali­zation and differentiation?

566. Trace theory of forgetting is otherwise known as:

(c) Theory of progressive changes in memory

(d) Retrieval-related forgetting

567. The Trace Theory of forgetting has a:

(b) Behaviouristic Orientation

(c) Structuralistic Orientation

(d) Functionalistic Orientation

(e) Psychoanalytic Orientation

568. Who argued that we perceive a thing as a whole and from this follows the organization in any psychological process including memory?

569. Who believed that what we learn leaves traces in the brain in the form of neural traces?

570. The Gestalists have approached the study of memory from the side of:

571. Who emphasized upon the fact that the memory trace of a figure must change progressively in the direction of a good stable figure?

572. According to Gestalt Psychologists, the or­ganized and well structured materials have:

573. Gestalt Psychologists held that our memory or any of our memory products never suffer from a complete:

574. Who has aptly remarked, “Memory has been tackled by Gestalts from the point of view of their study of perception”?

(b) Woodworth and Schlosberg

575. Sigmund Freud’s discovery of “Psycho- pathology of Everyday Life” reflects that:

(a) All forgettings are not motivated

(b) All forgettings are motivated

576. Several experimental findings indicate that incomplete or interrupted task is better learnt and retained than complete tasks. This is popularly known as:

(a) PQ4R method by Thomas and Robinson

577. Who is primarily responsible for qualitative measurement of retention?

578. Who held the view that remembering is primarily constructive rather than repro­ductive?

579. Who has written the classic book “Remem­bering”?

580. From many experimental studies, Bertlett concluded that the chief characteristic of remembering is:

581. Method of Repeated Reproduction is otherwise known as:

(a) Method of successive reproduction

(b) Method of Serial reproduction

582. Psychoanalytic theory of forgetting and Bertlett’s theory of remembering seek to explain:

(a) The causes of our day-to-day common forgettings

(b) Abnormal forgetting only

(c) Motivated forgetting only

(d) Photographic memory only

583. The phenomenon of “rumour” can be very successfully explained by:

(d) Bertlett’s theory of remembering

(e) Interference theory of forgetting

584. Experimental evidences indicate that reci­tation or rehearsal of materials is necessary to make learning:

(d) Organized and Systematic

585. The common sense view describing the cause underlying the process of forgetting is elaborated in terms of:

(d) Theory of Memory Traces

586. The phenomena of spontaneous recovery and reminiscences prove that disuse theory is:

(c) Applicable in case of photographic memory

(d) Applicable in case of Iconic memory

587. What happens in the interval between learning and recall determine the:

(c) Cause of Mnemonic Devices

588. The art of applying memory devices is called:

589. “A” learned a list of nonsense syllables without any rest in between trials. “B” learned the same list with a rest of 2 minutes in between trials. Whose retention score is expected to be higher?

590. Who has introduced the first systematic theory of motivated forgetting ?

591. A person took 8 trials to learn a list of nonsense syllables and took 6 trials to relearn the same list after two days. What was the percentage of his forgetting?

592. The process through which information coming from the sense is transformed, reduced, elaborated, recovered and used is called:

593. The branch of psychology which studies cognitive processes is known as:

594. The storage function of the sensory channels is called the:

595. In vision, the sensory storage seems to be in the form of a faint image called a/an:

596. Mnemonic systems organize information, so that it can be remembered, Mnemonic techniques are simple mental tricks such as rhymes or visual images which help us to improve our memory. The oldest mnemonic trick, which is credited to Greek poet Simonides, is:

597. Who held the view that memory trace changes according to the dynamic principles of organization?

598. Who viewed that retention or memory items are recorded in the form of neural traces in the brain automatically?

599. The Behaviouristically Oriented Psycho­logists introduced the concept of:

(a) Interferences as the basis of forgetting

600. Qualitative interpretations of forgetting came from:

Answers

501. (a) 502. (c) 503. (d) 504. (a) 505. (c) 506. (a) 507. (b) 508. (a) 509. (d) 510. (b) 511. (c) 512. (a) 513. (a) 514. (d) 515. (a) 516. (a) 517. (d) 518. (a) 519. (b) 520. (d) 521. (b) 522. (a) 523. (b) 524. (b) 525. (a) 526. (c) 527. (a) 528. (d) 529. (b) 530. (d) 531. (b) 532. (a) 533. (b) 534. (d) 535. (b) 536. (a) 537. (d) 538. (c) 539. (d) 540. (c) 541. (d) 542. (a) 543. (b) 544. (a) 545. (a) 546. (a) 547. (b) 548. (a) 549. (b) 550. (a) 551. (a) 552. (a) 553. (a) 554. (d) 555. (c) 556. (d) 557. (a) 558. (c) 559. (b) 560. (a) 561. (c) 562. (c) 563. (a) 564. (b) 565. (c) 566. (c) 567. (a) 568. (b) 569. (d) 570. (a) 571. (b) 572. (d) 573. (b) 574. (b) 575. (b) 576. (c) 577. (d) 578. (a) 579. (c) 580. (b) 581. (a) 582. (a) 583. (d) 584. (b) 585. (c) 586. (b) 587. (d) 588. (c) 589. (d) 590. (b) 591. (b) 592. (c) 593. (b) 594. (b) 595. (c) 596. (c) 597. (d) 598. (c) 599. (a) 600. (b)

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Introduction

This paper describes a replication of one of the most important early experiments in psychology, namely Ebbinghaus' classic experiment on forgetting from 1880 and 1885. We replicated the experiment that yielded the famous forgetting curve describing forgetting over intervals ranging from 20 minutes to 31 days. Ebbinghaus' goal was to find the lawful relation between retention and time-since-learning. This is why he fitted the data to two different functions (a power function, 1880, and a logarithmic function, 1885), as have many theorists since (e.g., [1,2–4]). This papers also includes an analysis—including one with a new model—of the shape of the Ebbinghaus' forgetting curve and its replications. Do the replicated forgetting curves have the same shape, or must we conclude that Ebbinghaus' forgetting curve was idiosyncratic and that quite different shapes may occur?

There is currently an increasing interest in replication studies in psychology, motivated by a growing uneasiness in the community about unreliable findings in psychology. It seems particularly important to try to replicate classic studies that are included in every textbook on cognitive psychology and may also be known by the general public. A good example of this is the classic study by Bartlett [5], which until 1999 had only had unsuccessful replication attempts, until finally Bergman and Roediger [6] succeeded in replicating the basic findings. One of the reasons earlier replications may have failed is because not all details were well-documented in the original study from 1932. The exact instructions, for example, were not included. This may explain why Wynn and Logie [7] had found the forgetting gradient in their experiment to be quite different from the one in Bartlett's experiment. Bergman and Roediger [6] also argue that this may have been caused by certain differences in the study design. Replication of classic experiments, thus, serves the dual purpose of verifying the reliability of the original results and uncovering more precisely how the original experiment was conducted.

It is hard to overestimate the importance of Hermann Ebbinghaus' contribution to experimental psychology. Influenced by the work of the German philosopher Herbart, he was the first to carry out a series of rigorous experiments on the shape of forgetting, which he completed in 1880. The experiment itself was preceded by a period in which he tried out a variety of materials and methods. After having tested himself with tones, numbers, and poem stanzas, he decided that none of these served his purposes. Tones were too cumbersome to handle and too difficult to reproduce for him, he did not find digits zero to nine suitable as basic units for the long-running experiments he envisioned, and the poem fragments he tried to learn (from Byron’s Don Juan) were deemed too variable in the meanings they evoked and therefore likely to cause measurement error [8] (p. 14–17). He, therefore, introduced nonsense syllables, which had more uniform characteristics than existing words or other verbal material. In his later experiments on learning, however, he did verify his results with the Don Juan verses, confirming both his main results on learning and his intuition that the latter stimuli did indeed yield much more variance in the data [9]. Since his introduction of nonsense syllables, a large number of experiments in experimental psychology has been based on highly controlled, artificial stimuli.

In all experiments reported by Ebbinghaus [9], he used only himself as a subject. Single-subject designs are not unusual in memory psychology. Especially in the study of autobiographical memory we find several diary studies based on one person’s personal memories (e.g., [10,11,12]). They have the advantage that there is no inter-subject variability, although they still require hundreds of trials to reduce the variance due to differences in stimuli and other factors. This places a great burden on the subject. Indeed, Ebbinghaus’ forgetting curve is based on seven months of experimenting, often up to three sessions per day. Wagenaar [13] meticulously recorded one daily memory during six years and spent several months recalling these.

A disadvantage of a single-subject design is that it remains unclear what the shape of forgetting would be with other subjects. Are the results universal or did the subject happen to have a memory that was exceptional in some way [14,15]. The generality of the results can be assessed with a faithful replication. There have been a number of—mostly early—replications of Ebbinghaus’s forgetting curve, notably by Radossawljewitsch [16] and Finkenbinder [17], but these authors used a much slower presentation rate of the stimuli of 2 s per stimulus, where Ebbinghaus learned at 0.4 s per stimulus. This was partially the result of the development of devices for mechanical presentation by Müller and colleagues [18,19], who presented materials at a rate one stimulus per second. Slowing down the presentation this much alters the nature of the processing with more time to generate meaningful associations to otherwise meaningless syllables. Though the resulting forgetting curves are clearly of interest to the field, we feel that the slow method of presentation form a large departure from Ebbinghaus’ original study. Also, Finkenbinder’s [17] longest retention interval is 3 days, instead of 31 days and though in the experiment by Radossawljewitsch [16] the retention interval range extends up to 120 days, his design suffers from an uneven distribution of intervals throughout time and time-of-day. Stimuli were learned in order: in the first few days of the study all 5 min intervals were learned, then the 20 min intervals, and so on. Because he did not use a pre-experimental practice phase, the early intervals took longer to learn while the subjects were still getting used to the materials and the procedure it is likely that this has affected the shape of the forgetting curve reported by him. There are other differences between these two studies and Ebbinghaus’, for example, the degree to which was learned and whether the subjects were allowed to pause between lists.

There are several unanswered questions about Ebbinghaus’ results that formed part of the motivation for us to undertake this replication. His basic stimulus was a ‘row’ of thirteen nonsense syllables, which he studied until he could correctly recall it in the correct order twice in succession. A question that seems pertinent is how stimuli at different serial positions were learned and how these were forgotten over time. Another question is how his measure of choice, namely savings (see below) is related to the nowadays more common measure of percentage correct. Finally, we were interested in the role of interference or fatigue in the course of the experiment.

To help answer these questions, we consulted not only the widely published text of 1885 [9], which was translated into English in 1913 [20], but also an earlier report of 1880 [8]. This is a handwritten manuscript that he submitted for his Habilitation, which in Germany is a requirement to be considered for a full professorship. This text (the so called Urmanuscript or original manuscript) has been typeset and republished in German in 1983. Even with this additional source, however, we still could not answer the questions above.

For these reasons, we decided to replicate Ebbinghaus’ forgetting experiment. If our replication yielded similar results, this would support the generality of Ebbinghaus’ curve and through a more detailed analysis of our data, we would be able to address the issues above. In the course of preparing for our study, we found that there has been at least one other replication study, namely by Heller, Mack, and Seitz [21]. This study has been published only in German, without an English abstract, and is not easily accessible at the time of writing, it is not available in electronic format (i.e., it is not available online) and it has never been cited in international journals in English. It is, however, a thorough study and an excellent replication attempt. Where the Ebbinghaus [8,9] texts are unclear about certain details, we have mostly followed Heller et al. [21] as a guideline so that we can also compare our results with theirs. Because we feel this is an important study that has not received the readership it deserves, we will mention more of its details here than we would have had it been more accessible at this point in time.

In 1885, Ebbinghaus introduces the savings measure of learning and memory (it does not appear in this form in his earlier text from 1880). Savings is defined as the relative amount of time saved on the second learning trial as a result of having had the first. Suppose, one has to repeat a list for 25 times in order to reach twice perfect recollection and that after one day, one needs 20 repetitions to relearn it. This is 5 less than the original 25 we can say that on relearning we saved 20% with respect to the original 25 rehearsals (5/25 = 0.2 or 20%). If it takes just as long to relearn the list as it took to learn it originally, then savings is 0. If the list is still completely known at the second trial (i.e., no forgetting at all), then savings is 1 or 100%. Ebbinghaus prefers to express savings in terms of time spent learning and relearning but the principle remains the same. After Ebbinghaus’ publication in 1885, the savings measure remained popular for several decades [16–19,22–24]. Eventually, researchers found the savings method too unreliable compared with other methods of measuring memory [24] and in the following decades it was used much less with some exceptions (e.g., [25]). Later, an important improvement was suggested [26,27], where learning is not to the 100% criterion but to a much lower one, such as 50% correct. These improved versions of the method are used nowadays, for example, when studying forgetting of foreign languages [28–30].

In the following, we will first report our replication experiment. Then, in the Discussion section we will revisit the shape of forgetting, analyze the effects of serial position on forgetting, and investigate what mathematical equations present a good fit to the Ebbinghaus forgetting curve and its replications. Finally, we will study whether there is evidence for a jump at 24 hours in these curves, which some authors have attributed to the effect of sleep.


Memory and Forgetting (Hermann Ebbinghaus – 1885)

As generally accepted methods of inquiry transitioned from philosophical reasoning to quantitative scientific inquiry in the latter half of the 19 th century, Hermann Ebbinghaus built on Aristotle’s foundation of the association of ideas by conducting the first recorded experimental studies of memory.[1] His desire was “to go a step farther into the workings of the mind and to submit to an experimental and quantitative treatment the manifestations of memory” (1913, p. v). The experiments were conducted from 1879 to 1880 and from 1883 to 1884. In his study he explored “the rapidity of learning series of syllables as a function of their length,” “the increase in rapidity of learning in the case of meaningful material,” “retention as a function of the number of repetitions,” “the effect of a decided increase in the number of repetitions,” “retention and obliviscence as a function of time,” “retention as a function of repeated learning,” and” retention as a function of the order of succession of the members of the series.”

Though his experiments were conducted using himself as the only subject of experimentation, and though he acknowledged and qualified many times in his writing, that the results of the tests are of limited individual significance, his findings are nevertheless very interesting, and have been applied quite broadly.

In the process of conducting his experiments, one of the first things he noticed is that, for him at least, a series of seven[2] or fewer syllables required only a single reading in order to recite it perfectly (Ebbinghaus, 1913, p. 48). Multiple readings were required before the first unaided reproduction was possible for lists of length greater than seven. The significance of this observation is that the capacity of immediate memory is clearly limited to active retention of a rather small number of items, and that learning generally happens through repeated experience:

Under ordinary circumstances, indeed, frequent repetitions are indispensable in order to make possible the reproduction of a given content. Vocabularies, discourses, and poems of any length cannot be learned by a single repetition even with the greatest concentration of attention on the part of an individual of very great ability. By a sufficient number of repetitions their final mastery is ensured, and by additional later reproductions gain in assurance and ease is secured. (Ebbinghaus, 1913, p. 4)

He found that neither an excess nor an insufficiency of repetition was harmful to learning, or entirely wasteful:

What will happen, it may be asked, if the number of repetitions actually given to a certain series is less than is required for memorization or if the number exceeds the necessary minimum?

The general nature of what happens has already been described. Naturally the surplus repetitions of the latter alternative do not go to waste. Even though the immediate effect, the smooth and errorless reproduction, is not affected by them, yet they are not without significance in that they serve to make other such reproductions possible at a more or less distant time. The longer a person studies, the longer he retains. And, even in the first case, something evidently occurs even if the repetitions do not suffice for a free reproduction. By them a way is at least opened for the first errorless reproduction, and the disconnected, hesitating, and faulty reproductions keep approximating more and more to it. (Ebbinghaus, 1913, p. 52)

This phenomenon he described metaphorically, as a process of engraving and fading:

These relations can be described figuratively by speaking of the series as being more or less deeply engraved in some mental substratum. To carry out this figure: as the number of repetitions increases, the series are engraved more and more deeply and indelibly if the number of repetitions is small, the inscription is but surface deep and only fleeting glimpses of the tracery can be caught with a somewhat greater number the inscription can, for a time at least, be read at will as the number of repetitions is still further increased, the deeply cut picture of the series fades out only after ever longer intervals. (Ebbinghaus, 1913, pp. 52-53)

He found that increased repetition during a period of study provided a savings in relearning at a later period. Specifically, he found that for each three additional repetitions that he spent on a given day on the study of a series, he saved, in learning that series 24 hours later, on the average, approximately one repetition (Ebbinghaus, 1913, p. 57). But he also learned that this was of limited effect. The savings of relearning did not continue to increase proportionally with an increased number of repetitions above a certain limit:

I have made some trial tests partly with shorter series, and partly with familiar series, all of which confirmed the result that the proportion in question gradually ceases to hold with a further increase of repetitions. Measured by the saving of work after 24 hours the effect of the later repetitions gradually decreases. (pp. 59-60)

The effect of increasing the number of repetitions of series of syllables on their inner fixedness in the above defined sense grew at first approximately in proportion to the number of repetitions, then that effect decreased gradually, and finally became very slight when the series were so deeply impressed that they could be repeated after 24 hours, almost spontaneously. (p. 61)

In addition to looking at the effect of an increased number of repetitions during a given period of study, he also examined the effect of multiple periods of study on retention of what has been learned. He found that each subsequent relearning of a series strengthens its retention:

The series are gradually forgotten, but—as is sufficiently well known—the series which have been learned twice fade away much more slowly than those which have been learned but once. If the relearning is performed a second, a third or a greater number of times, the series are more deeply engraved and fade out less easily and finally, as one would anticipate, they become possessions of the soul… (Ebbinghaus, 1913, p. 81)

In conjunction with his investigation on the effect of repeated learning, he also asked whether it was better to study all at once, or to break the task down into multiple periods of study. He found that for the relearning of a 12-syllable series, “38 repetitions, distributed in a certain way over the three preceding days, had just as favorable an effect as 68 repetitions made on the day just previous” (p. 89). Though based on a limited data set, Ebbinghaus felt that the difference was significant enough to warrant a conclusion in favor of spaced practice:

Even if one makes very great concessions to the uncertainty of numbers based on so few researches, the difference is large enough to be significant. It makes the assumption probable that with any considerable number of repetitions a suitable distribution of them over a space of time is decidedly more advantageous than the massing of them at a single time.

With this result, found here for only very limited conditions, the method naturally employed in practice agrees. The schoolboy doesn’t force himself to learn his vocabularies and rules altogether at night, but knows that he must impress them again in the morning. A teacher distributes his class lesson not indifferently over the period at his disposal but reserves in advance a part of it for one or more reviews. (p. 89)

He also noted, however, that an important factor which affected his ability to learn was the time of day at which he studied, with morning hours being more productive than the later hours of the day:

In the later hours of the day mental vigor and receptivity are less. The series learned in the morning and then relearned at a later hour, aside from other influences, require more work for relearning than they would if the relearning were done at a time of mental vigor equal to that of the original learning. (Ebbinghaus, 1913, p. 66)

Ebbinghaus is perhaps most well known for his description of what is commonly referred to as the forgetting curve:

Left to itself every mental content gradually loses its capacity for being revived, or at least suffers loss in this regard under the influence of time. Facts crammed at examination time soon vanish, if they were not sufficiently grounded by other study and later subjected to a sufficient review. But even a thing so early and deeply founded as one’s mother tongue is noticeably impaired if not used for several years. (1913, p. 4)

He discovered that the rate of forgetting could be approximated quite accurately by a negatively accelerated, exponential logarithmic function where the amount remembered, b, is calculated as a function of time (in minutes), t, which have passed, counting from one minute before the end of learning (pp. 76-79), where the constants k and c are given values of 1.84 and 1.25, respectively:

In addition to repetition and forgetting, Ebbinghaus also had something to say about individual differences, content-type effects of learning, attention and interest, meaningfulness, content-length effects on learning, the influence of recollection on reproduction, capacity, and order effects on the association of ideas learned in series. In regard to individual differences, he simply noted that individuals vary in their ability to memorize, and that the capacity of a given person varies with age and time of day (1913):

How differently do different individuals behave in this respect! One retains and reproduces well another, poorly. And not only does this comparison hold good when different individuals are compared with each other, but also when different phases of the existence of the same individual are compared: morning and evening, youth and old age, find him different in this respect. (p. 3)

He also noted that the type of content to be learned is of great influence on the amount of effort required to learn it (1913):

Melodies may become a source of torment by the undesired persistency of their return…Forms and colors are not so importunate and if they do return, it is with noticeable loss of clearness and certainty…It is with something of a struggle that past states of feeling are realized when realized, and this is often only through the instrumentality of the movements which accompanied them, they are but pale shadows of themselves. (p. 3)

Furthermore, the combination of content type and individual differences is the source of great variation in the work required to learn (1913):

If the two foregoing points of view are taken together—differences in individuals and differences in content—an endless number of differences come to light. One individual overflows with poetical reminiscences, another directs symphonies from memory, while numbers and formulae, which come to a third without effort, slip away from the other two as from a polished stone. (p. 3)

Additionally, he noted that the intensity of attention and interest play a significant role:

Very great is the dependence of retention and reproduction upon the intensity of the attention and interest which were attached to the mental states the first time they were present. The burnt child shuns the fire, and the dog which has been beaten runs from the whip, after a single vivid experience. People in whom we are interested we may see daily and yet not be able to recall the color of their hair or of their eyes. (pp. 3-4)

That which carries greater meaning for the learner is more easily acquired. In comparing the learning of series of nonsense syllables to the learning of a poem, Ebbinghaus found a very large difference between the number of repetitions required to learning nonsense material and the number of repetitions required to learn that which was meaningful:

In order to keep in mind the similarities and differences between sense and nonsense material, I occasionally made tests with the English original of Byron’s “Don Juan.” These results do not properly belong here since I did not vary the length of the amount to be learned each time but memorized on each occasion only separate stanzas. Nevertheless, it is interesting to mention the number of repetitions necessary because of their contrast with the numerical results just given.

[When learned to the point of the first possible reproduction] each stanza required hardly nine repetitions or, if the errorless reproduction is abstracted, scarcely eight repetitions.

If it is born in mind that each stanza contains 80 syllables (each syllable, however, consisting on the average of less than three letters) and if the number of repetitions here found is compared with the results presented above, there is obtained an approximate numerical expression for the extraordinary advantage which the combined ties of meaning, rhythm, rhyme, and a common language give to material to be memorised [sic]. If the above curve is projected in imagination still further along its present course, then it must be supposed that I would have required 70 to 80 repetitions for the memorisation [sic] of a series of 80 to go nonsense syllables. When the syllables were objectively and subjectively united by the ties just mentioned this requirement was in my case reduced to about one-tenth of that amount [italics added]. (Ebbinghaus, 1913, pp. 50-51)

The curve referred to is that which resulted from plotting “the number of repetitions necessary for the memorisation [sic] of series in which the number of syllables progressively increased” (p. 48). Where the length of the series was seven or less, only one reading was necessary before the list could be recited perfectly, with lists of fewer than seven items requiring less and less attention. As the length of the series was increased, the number of repetitions required to learn the series increased non-linearly, with the ascent of the curve at first being very steep, but gradually flattening out.

The increased number of repetitions required to learn the series initially also had the side effect of establishing it more firmly in the mind:

…the effect of this need of more numerous repetitions in the cases investigated consists not merely in making the series just reproducible, but also in the firmer establishment of the longer series. After an interval of 24 hours they could be relearned to the point of being just reproducible with a saving both absolutely and relatively greater than with the shorter series.” (p. 84)

As a result of this “firmer establishment” longer lists could be more easily relearned:

On each day the average number of repetitions necessary for the committing of a given series is less than on the preceding day. With the longer series, in whose case the first output of energy is great, the decrease in the amount of work each time necessary to reach the first possible reproduction is proportionally rapid. With the shorter series, where the first output is small, the decrease is proportionally slow. (p. 85)

Another very interesting yet subtle observation was that whether or not he could remember studying a series of lists on a previous day made no difference in the effort required to master the series (1913):

When the series were repeated 8 or 16 times they had become unfamiliar to me by the next day. Of course, indirectly, I knew quite well that they must be the same as the ones studied the day before, but I knew this only indirectly. I did not get it from the series, I did not recognise [sic] them. But with 53 or 64 repetitions I soon, if not immediately, treated them as old acquaintances, I remembered them distinctly. Nothing corresponding to this difference is evident in the times for memorisation [sic]and for savings of work respectively. They are not smaller relatively when there is no possibility of recollection nor larger relatively when recollection is sure and vivid. The regularity of the aftereffect of many repetitions does not noticeably deviate from the line that is, so to speak, marked out by a smaller number of repetitions although the occurrence of this after-effect is accompanied by recollection in the first case just as indubitably as it lacks recollection in the second case. (pp. 58-59)

In the final chapter of his book, Ebbinghaus reported his findings regarding the mental association between members of a series, measured by the savings observed when learning a new series methodically constructed from a series previously learned through the omission of 1, 2, 3 or seven intermediate members. His findings provide empirical support in favor of Aristotle’s law of contiguity. The new series formed by leaving out intermediate members from the original series were learned with a time savings that was greatest where fewer intermediate members were omitted (1913):

There seems to be an association not merely in direct but also in indirect succession. The strength of these connections decreases with the number of the intervening numbers with a small number it was, as will be admitted, of surprising and unanticipated magnitude. (p.101)

In contrast to this observed savings—yet still consistent with the idea that mental concepts are associated with one another, and that the order of succession is one of the characteristics learned when learning a series—he also found that when a new series was constructed not by omitting intermediate members of the original series but by permutation of the members (i.e., changing the order) there was an increase in the expenditure of time required to learn the new series, suggesting that the ordering of the original list interfered with the learning of the new list (1913):

By derivation of the transformed series by skipping I, 2, 3, 7 intermediate syllables, the derived series were therefore learned with an average saving of 110, 79, 64, 40 seconds. On the contrary with derivation of the series by permutation of the syllables the learning required an average increase in expenditure of 5 seconds. (p. 104)

He also found that there was a present, yet weaker, reciprocal association formed between the members of a series. When the transformed series is formed by mere reversal of the syllable sequence, there is a time savings in learning of the transformed series, as compared to learning an unrelated, arbitrary series of the same length:

As a result of the learning of a series certain connections of the members are therefore actually formed in a reverse as well as in a forward direction…The strength of the predispositions thus created was again a decreasing function of the distance of the members from each other in the original series. It was, however, considerably less for the reverse connections than for the forward ones, the distances being equal. (pp. 112-113)

The studies that Ebbinghaus conducted were rooted in the ideas of association, but were clearly mentalistic, in contrast with the contemporary behavioristic S-R theories of Pavlov and Thorndike. As such, Ebbinghaus’s studies provided a precedent on which much of the cognitive learning research conducted during the 20 th century was based.

[1] Though often cited unequivocally as the first experimental studies of memory, given the inquisitive nature of man, and evidence of man’s methodological inspection of both the external and internal realm since the time of the early Greeks, it is unlikely that it actually is the first. That said, until some predating study is identified, comparable in clarity and coherence, we accept it as such.

[2] In 1956, George A. Miller published The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information (Miller, 1956). Though he didn’t specifically cite Ebbinghaus’s study, he was not unaware of its existence (p. 94). In his article Miller cited several examples in which the unidimensional channel capacity—operationally defined based on information theory as the number of bits a person was able to take as input which varied along a single scale and then pass on as output, usually in a verbal absolute judgment or report—was found to be sufficient to represent 7 distinct elements, plus or minus two. For absolute judgments of tones it was found that listeners never confused two or three distinct tones, rarely confused four, but with five or more confusions were frequent. Psychologists “have been using seven-point rating scales for a long time, on the basis that trying to rate into finer categories does not really add much to the usefulness of the ratings” (p. 84). Channel capacity for absolute judgments of loudness average 2.3 bits, or enough to represent about five discriminable alternatives. For taste discrimination, 1.9 bits, or four distinct concentrations can be identified—less distinctive than auditory stimuli, but not far off. Visual capacity seems to have a much higher capacity, ranging from 3.2 to 3.9 bits, meaning 10 to 15 distinct positions along a linear interval can be uniquely identified. Channel capacity for the skin was found to have “about four intensities, about five durations, and about seven locations” (p. 86).

Miller’s conclusion was that “there seems to be some limitation built into us either by learning or by the design of our nervous systems, a limit that keeps our channel capacities in this general range” (p. 86). Miller also notes, however, that in everyday experience we are able to “identify accurately any one of several hundred faces, any one of several thousand words, any one of several thousand objects, etc.” (p. 87) This he attributes to our ability to make simultaneous and successive discriminations. With simultaneous discriminations “we can make relatively crude judgments of several things simultaneously” (p. 88) thereby increasing our total capacity. Language is made up of sequences of phonemes, so we are able to make several judgments successively as we process the input. Our span of immediate memory exhibits a similar trait in that it seems to be limited to about seven items in length. Miller is quick to point out that while the limits of absolute judgment and immediate memory are similar, we should not jump to the conclusion that they are rooted in the same source, although that may be the case.

In his article several years later, entitled, “The Magical Number Seven: Still Magic After All These Years?,” Baddeley (1994) concluded that:

In emphasizing the importance of recoding, Miller pointed the way ahead for the information-processing approach to cognition, and in developing the concept of chunking, he provided a concept that continues to be fruitful in the analysis of learning and memory. The article, if not the number seven, retains its magic. (p. 356)


Hermann Ebbinghaus

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Hermann Ebbinghaus, (born January 24, 1850, Barmen, Rhenish Prussia [Germany]—died February 26, 1909, Halle, Germany), German psychologist who pioneered in the development of experimental methods for the measurement of rote learning and memory.

Ebbinghaus received a Ph.D. degree from the University of Bonn in 1873. Shortly thereafter he became assistant professor at the Friedrich-Wilhelm University, Berlin, a post he held until 1894, when he was appointed professor at the University of Breslau.

Using himself as a subject for observation, Ebbinghaus devised 2,300 three-letter nonsense syllables for measuring the formation of mental associations. This learning invention, together with the stringent control factors that he developed and his meticulous treatment of data, brought him to the conclusion that memory is orderly. His findings, which included the well-known “forgetting curve” that relates forgetting to the passage of time, were reported in Über das Gedächtnis (1885 Memory).

After completing his work on memory, Ebbinghaus turned to research on colour vision and in 1890, with the physicist Arthur König, founded the periodical Zeitschrift für Psychologie und Physiologie der Sinnesorgane (“Journal of the Psychology and Physiology of the Sense Organs”). In conjunction with a study of the mental capacities of Breslau schoolchildren (1897), he created a word-completion test. That same year the first part of another work on which his reputation rests, Grundzüge der Psychologie (1902 “Principles of Psychology”), was published. In 1905 he left Breslau for the University of Halle, where he wrote a still more popular work, Abriss der Psychologie (1908 “Summary of Psychology”). Ebbinghaus’ research showed that, contrary to prevailing beliefs, scientific methods could be applied to the study of the higher thought processes.


Ebbinghaus hypothesized that difference in memory strength between individuals could be somewhat triumphed over by simple training in mnemonic techniques. Two of the methods he asserted to be among the best ways to increase strength of memory are:

  1. Better memory representation (e.g. with mnemonic techniques)
  2. Repetition based on active recall (esp. spaced repetition)

He believed that each repetition in learning leads to increase in the interval for when the next repetition is required. It was later discovered that higher original learning also lead to slower loss in memory.

For instance, taking time to repeat information every day during exams decreases the effects of the forgetting curve. According to research, information should be repeated within the first 24 hours of learning to reduce the rate of memory loss.

Note: Not all memories follow the forgetting curve as there could be various other factors in play, such as noise and other environmental factors. Because of their influence on what information is remembered, not all memories are affected by detrimental effects of interference.


Ebbinghaus like model for retention of details from experience - Psychology

" Ebbinghaus is dead. But his oeuvre is alive "

"Ebbinghaus est mort. Mais ses œuvres vivent"

Si Hermann Ebbinghaus (1850-1909) n'a pas publié beaucoup d’articles et d’ouvrages de son vivant [2] (près de 30 références contre par exemple près de 300 pour Alfred Binet) et s'il a formé peu d'élèves connus à part William Stern (1867-1947) (on dit d'ailleurs qu'il ne les recherchait pas), on doit admettre, d'une part, que ce n'est qu'un pauvre indice de son activité scientifique pour un homme de cette stature et de cette réputation [3] et, d'autre part, que l'influence exercée n'en a pas moins été considérable. Ses écrits ont en effet eu un grand retentissement sur ses contemporains et bien au-delà sur les psychologues expérimentalistes tout au long du XXe siècle [4] .

If Hermann Ebbinghaus (1850-1909) did not publish many articles and books during his life [2] (around 30 references compared to almost 300 by Alfred Binet) and if he had only few well known students apart from William Stern (1867-1947) (it seems that he did not actively seek them), it has to be admitted, on the one hand, that these might be rather poor indicators of the scientific activities for a man of such kind of stature and reputation [3] and, on the other hand, that his influence in the field was indeed quite substantial. His writings had a considerable effect on and attracted broad attention by his contemporaries, and even more by the experimental psychologists of the 20 th century [4] .

Son indépendance et son originalité de pensée se retrouvent lorsqu'on constate par exemple qu'il n'a pas créé d'école de psychologie et qu'il peut difficilement être rattaché à un courant psychologique de l'époque [5] . Pourtant, comme nous le verrons, Ebbinghaus va être influencé tout au long de sa carrière scientifique par les écrits de l'un de ses compatriotes : Gustav Th. Fechner (1801-1887) [6] .

The fact that he did not establish a school of psychology and that it is difficult to associate him with a psychological stream of his time may be considered as a sign of his independence and the uniqueness of his ideas [5] . However, as we shall see, Ebbinghaus had been affected all the long of his scientific career by the writings of one of his compatriots: Gustav Th. Fechner (1801-1887) [6] .

La meilleure manière d'exposer la vie et l'œuvre de ce psychologue est certainement de prendre pour fil conducteur les différentes étapes de sa formation et de sa carrière scientifique. L'avantage de ce type de présentation est qu'il nous permettra de souligner dans une perspective diachronique ses contributions essentielles dans le domaine de la mémoire humaine (et dans celui d'autres fonctions psychologiques) ainsi que son apport au niveau de la diffusion du savoir scientifique.

The best way to depict the life and work of this psychologist is certainly to take the different stages of his formation and his scientific career as guidelines. The advantage of this way of exposition is supported by the opportunity to underline his essential contributions in the domain of the human memory (and to other fields of psychological functions) as well as his influence on the diffusion of scientific knowledge in a diachronic perspective.

Premiers pas dans la formation d’un psychologue expérimentaliste

Hermann Ebbinghaus est né en Prusse, à Barmen aujourd'hui un quartier de Wuppertal près de Bonn, en Rhénanie, le 23 janvier 1850 de Carl Ebbinghaus (1815-1866), négociant en papier et textile, et de Juliane Ebbinghaus, née Klewitz (1815-1880). De confession luthérienne, il fit ses études primaires et secondaires dans sa ville natale [7] .

Hermann Ebbinghaus was born on January 23, 1850 in Barmen, Prussia, today a quartier of Wuppertal near Bonn, Rhineland, from Carl Ebbinghaus (1815-1866), a trader of paper and textile, and Juliane Ebbinghaus, born Klewitz (1815-1880). He was raised in the spirit of Lutheranism and he visited the primary as well as the secondary school in his hometown [7] .

Il entreprend ses études universitaires à Bonn à l'automne 1867 et, plus tard, selon la mode du temps qui est de se rendre de ville universitaire en ville universitaire, il se rend à Berlin et à Halle pour étudier les langues classiques, l'histoire et la philologie. En 1870, il sert pendant un an dans l'armée prussienne durant la guerre contre la France (1870-1871). C'est au printemps 1871 qu'il décide de se consacrer entièrement à la philosophie. Il reçoit son grade de Docteur à Bonn le 16 août 1873 en ayant brillamment soutenu, selon Karl Marbe (1869-1953), une thèse dont le sujet était à la mode et qui avait pour titre : « Über die Hartmannsche Philosophie des Unbewussten » ("sur la Philosophie de l'Inconscient de Hartmann"). L'ouvrage philosophique d'Eduard von Hartmann sur l'inconscient [8] était un best-seller à l'époque. La première édition allemande de cette œuvre date de 1869 et fut à maintes fois rééditée durant la décennie suivante (une traduction française a même été publiée chez Félix Alcan en 1877 [9] ). Dans sa thèse, Ebbinghaus se montra très critique envers l'auteur qui niait toute continuité et transition entre la conscience et l'inconscient en soutenant l'existence d'un inconscient absolu et métaphysique. Influencé par les positions de Leibniz, il devint partisan de la loi de continuité. Mais il avait bien conscience que sa prise de position ne s'appuyait pas sur des preuves objectives solides mais sur un raisonnement subjectif. Cette constatation l'amena, d'une part, à affirmer que la psychologie devrait être séparée de la philosophie et, d'autre part, que la nouvelle psychologie devrait s'appuyer sur les méthodes objectives utilisées par les sciences naturelles [10] . Comment mettre en place une psychologie scientifique ? Ebbinghaus n'en savait encore rien à l'époque. Il lui fallut attendre quelques années pour que son projet prenne forme.

He started his university studies in the fall of 1867 in Bonn later - according to the fashion of the time which meant to visit several universities - he went to Berlin and Halle to study classical languages, history and philology. In the year 1870, he served in the Prussien army during the war against France (1870-1871) for one year. Then, in the spring of 1871 he decided to concentrate his studies completely on the subject of philosophy. On August 16, 1873 he received his doctoral degree from the University of Bonn after a brilliant defense of his thesis, as reported by Karl Marbe (1869-1953) the topic of his thesis was very trendy in those times and had the following title: « Über die Hartmannsche Philosophie des Unbewussten » ("On the philosophy of the unconscious according to Hartmann"). The philosophical work by Eduard von Hartmann on the unconscious [8] was a bestselling book of the time. The first edition of this book (in German) was published in the year 1869 and during the following decade there were several re-editions (a French translation was published already in 1877 by Félix Alcan an English translation by William Chatterton Coupland was published in 1884 by Macmillan, New York [9] ). In his thesis, Ebbinghaus took a quite critical position towards Hartmann who denied any continuity or transition of the conscious and the unconscious and emphasized the existence of an absolute and metaphysical unconscious. Guided by the position of Leibniz, he became an advocate of the law of continuity. However, he was aware that his position was not sustained by any objective and solid arguments but rather by subjective reasons. From this ascertainment he concluded that the discipline of psychology should be separated from philosophy that the new science of psychology should make use of objective methods, namely those used in in the natural sciences [10] . How to establish a scientific psychology? At this time, Ebbinghaus didn’t have a clue. He had to wait a couple of years before his project did take shape.


D'après Boring [11] , Ebbinghaus passa les deux années suivantes à Berlin, mais Shakow [12] nous dit qu'on sait seulement qu'il projetait d'aller dans cette ville. Durant les années 1875-1878 il étudia en auditeur libre et voyagea en Angleterre et en France où il fut précepteur et enseignant [13] . C'est à cette époque qu'il se procura les "Elemente der Psychophysik" (1860) de Gustav Theodor Fechner qui devaient lui démontrer que la psychologie peut utiliser avec profit les méthodes des sciences naturelles. On a cru pendant longtemps que c'était à Paris qu'il acheta d'occasion les deux tomes de cet ouvrage [14] , mais cette localisation a plus récemment été remise en question [15] puisqu'on admet aujourd'hui qu'il les a acquis entre avril et décembre 1875 à Londres. Cette dernière hypothèse est d'ailleurs admise maintenant [16] .

According to Boring [11] , Ebbinghaus spent his next two years in Berlin, but Shakow [12] mentions that he only intended to go to this town. During the years 1875 to 1878 he studied as a guest student and travelled around in England and in France, where he worked as a tutor and a teacher [13] . It was during this period of time that he purchased the book "Elemente der Psychophysik" (1860) by Gustav Theodor Fechner, a book which convincingly demonstrated him the benefits of natural science methods for psychology. For a long time it was assumed that it was in Paris where he bought the two volumes of this opus (second hand) [14] , however more recently there were doubts about that [15] currently there is a broad consent that he bought them in London between April and December 1875 [16] .

Quoi qu'il en soit, profondément impressionné par l'utilisation de la méthode expérimentale pour l'étude de la sensation après la lecture de l'ouvrage de Fechner [17] , Ebbinghaus eut l'idée de l'appliquer à l'étude de la mémoire, peut être parce qu'en tant que jeune philosophe voyageant en Angleterre il s'était intéressé tout naturellement à la psychologie associationniste britannique. Ses premières recherches commencèrent avec des enfants dont il avait la charge en Angleterre [18] et surtout en France entre les années 1877 et 1878 [19] . Les premières recherches expérimentales d'Ebbinghaus sur la mémoire semblent avoir débuté en France au cours de l'hiver 1877-78 alors qu'il venait juste de quitter son emploi de précepteur chez la marquise Armande de Seguier d'Avaray (1835-1912) et de s'installer à Paris au quartier Montmartre en exerçant le métier de professeur d'allemand. L'étude expérimentale qu'il a menée fut néanmoins une tentative avortée d'améliorer par la pratique l'empan des nombres en mémoire immédiate [20] . Les autres travaux, qui ont été entrepris en employant des matériels d'apprentissage aussi divers que des sons et des poèmes, lui montrèrent cependant la difficulté de travailler avec les enfants, ce qui l'incita ultérieurement à se prendre lui-même comme sujet d'expérience. Il quitte Paris le 20 juillet 1878 pour Postdam, après avoir appris sa nomination à la cours impériale de Berlin en tant que tuteur de français du Prince Waldemar von Hohenzollern (1868-1879) qui devait malheureusement disparaître prématurément. Ses fameuses recherches sur la mémoire ont débuté au cours de l'hiver 1878-1879 avec la construction de son matériel expérimental. Ses premières recherches expérimentales formèrent le corps de sa thèse d'habilitation (Ebbinghaus, 1880) soutenue le 23 avril 1880 à l'Université de Berlin [21] puis furent complétées dans son ouvrage sur la mémoire de 1885 [22] .

In any case, after having read the work by Fechner, Ebbinghaus was deeply impressed by the application of experimental methods in the study of sensation [17] . He had the idea to apply it for the study of memory, possibly because of his rising interest in the British psychology of associationism while travelling in England. He carried out his first research steps with children for whom he was in charge of when he was in England [18] and then in France during the years of 1877 and 1878 [19] . Ebbinghaus’ experimental studies on the topic of memory seemed to have started in France during the winter of 1877-1878 he had just resigned from his job as a tutor employed by the Marquise Armande de Seguier d'Avaray (1835-1912) and resided then in the Montmartre quarter in Paris earning his living as a teacher of German. He conducted an experimental study which was however an unsuccessful attempt to increase the immediate memory span for numbers [20] . Further studies he carried out with very diverse materials like sounds and poems, and they showed him how difficult it was to do experiments with children ultimately, it was this experience that brought him to the point, to be his own experimental subject. He left Paris on July 20, 1878 for Postdam, after having been appointed by the imperial court of Berlin as a teacher of the French language for Prince Waldemar von Hohenzollern (1868-1879), who however passed away very shortly. He started his famous research on memory during the winter 1878-1879 with the construction of the experimental materials. His first experimental studies were the central part of his habilitation thesis (Ebbinghaus, 1880), which he defended on April 23, 1880 at the University of Berlin [21] these studies were later completed and published in 1885 as his legendary book on memory [22] .

L’étude expérimentale de la mémoire (1879-1885)

Experimental studies on memory (1879-1885)

Depuis la rédaction de sa thèse sur von Hartmann, Ebbinghaus ne considérait plus la psychologie seulement comme la science de la conscience mais aussi celle de l'inconscient. Cette position n'allait pas réellement à contre courant des idées de l'époque puisque l'existence de l'inconscient était généralement admise dans les milieux philosophiques et scientifiques durant les dernières décennies du XIX e siècle. Il fut, on le sait, profondément influencé durant ses années de formation par les écrits d'un autre philosophe, Johann Friedrich Herbart (1776-1841) [23] , qui considérait que les représentations mnésiques inconscientes pouvaient agir sur la pensée et le comportement conscient. Contrairement à Herbart et aux psychologues expérimentalistes de son époque, comme le fameux Wilhelm Wundt (1832-1920), Ebbinghaus pensait pourtant qu'une science expérimentale des processus mentaux supérieurs était possible. Ainsi, il fut non seulement, d'une part, historiquement l'un des premiers à prendre en compte l'expression inconsciente des phénomènes psychiques mais aussi et surtout, d'autre part, celui qui a montré que la méthode expérimentale pouvait être utilisée pour aborder l'étude des fonctions psychologiques supérieures. Comme il soutenait depuis 1873 l'hypothèse de continuité déjà avancée par Leibniz et Herbart, on pouvait tout naturellement s'attendre à ce qu'il étudie la mémoire dans son acception globale à la fois consciente et inconsciente [24] . Il adopta ainsi les méthodes psychophysiques utilisées par Fechner dans le domaine de la sensation et les adapta à l'étude de cette nouvelle entité psychologique. [25]

From the writing of his thesis on the topic of von Hartmann onwards, Ebbinghaus didn’t consider psychology as being solely the science of conscious, but as well of unconscious behavior. This position wasn’t completely in opposition to the ideas of the epoch as the existence of the unconscious was generally accepted in philosophical and scientific circles of the last decades of the 19 th century. During the years of his formation he had been profoundly influenced by the writings of another philosopher, Johann Friedrich Herbart (1776-1841) [23] , who postulated that unconscious mental representations were able to operate on conscious thoughts and behavior. However, contrary to Herbart and to the experimental psychologists of his time, like for instance the famous Wilhelm Wundt (1832-1920), Ebbinghaus was nevertheless convinced that an experimental scientific approach towards higher mental processes was possible. Therefore, from a historic perspective, he was not only among the first scientists to consider unconscious expressions of psychological experiences, but as well, and in particular, the one who has demonstrated that the experimental method was very suitable to study higher psychological functions. As he adhered to the hypothesis of continuity (already since 1873), which had already been advanced by Leibniz and Herbart, it was to be expected that he would study memory in a wide-ranging way and take into account conscious as well as unconscious aspects [24] . Therefore he adopted the methods of psychophysics which Fechner had been using in the domain of sensation and he adapted them in order to study new psychological entities [25] .

La thèse d’habilitation (1880)

Habilitation thesis (1880)

S'appliquant surtout à ne pas réduire la mémoire au souvenir conscient, il décida ainsi de développer un indicateur basé sur l'économie en temps ou en nombre d'essais réalisée lors d'un second apprentissage : La méthode utilisée fut celle communément appelée l'économie au réapprentissage (pour une présentation : Nicolas, 1992). Cette méthode avait l'avantage de pouvoir aborder l'étude de cette fonction psychologique sans pour autant la réduire à son expression consciente. De plus, afin de favoriser l'étude objective de la mémoire, Ebbinghaus décida d'introduire un matériel nouveau [26] (des séries sans signification de syllabes) qui réduise autant que possible l'influence de la signification (c'est Müller et Schumann [27] en 1893-1894 qui utilisèrent pour la première fois non pas des séries mais des syllabes sans signification) et des méthodes quantitatives susceptibles d'appuyer ses conclusions. Sans aide et sans laboratoire, il développa ainsi pendant plus d'une année, au cours d'un effort solitaire monumental (étant lui-même le sujet de toutes les expériences), une longue série d'investigations expérimentales dans ce domaine [28] . Il lisait chaque série de syllabes à haute voix au rythme rapide d'environ 150 unités à la minute. Après une pause de quinze secondes, une deuxième lecture commençait. Les lectures successives se poursuivaient jusqu'à ce qu'il soit certain de sa capacité à prédire les syllabes suivantes. Les lectures s'arrêtaient dès qu'il parvenait à réciter à vitesse rapide la série complète correctement deux fois consécutivement dans l'ordre de présentation. La phase de test n'était pas différente de la phase d'étude puisque Ebbinghaus répétait l'activité d'apprentissage précédente (méthode de réapprentissage) jusqu'au critère de maîtrise parfait (il n'entreprenait aucun effort de souvenir sur les séries préalablement étudiées). L'économie réalisée en durée d'apprentissage ou en nombre d'essais constituait un indicateur du taux de rétention de l'information depuis sa première présentation. C'est l'utilisation de cette ingénieuse variable dépendante qui constitue la traduction expérimentale de ses réflexions théoriques sur le problème mnésique. Il étudia ainsi : 1) le nombre de répétitions nécessaires à l'apprentissage d'une série 2) l'économie en fonction du nombre de répétitions initiales 3) les effets de l'apprentissage répété sur l'économie au réapprentissage 4) mais ce sont surtout ses expériences sur l'oubli en fonction du temps qui sont au centre de son travail initial sur la mémoire [29] .

Because he did not want to reduce memory on conscious recall, he decided to develop an indicator which was based on the measurement of the time or the number of trials necessary for a second learning episode: This measure or indicator is usually termed savings for relearning (see Nicolas, 1992). This method has the advantage that it allows to assess mental indicators without the restriction to conscious manifestations. Furthermore, in order to study memory in an objective way, Ebbinghaus introduced a new type of learning material [26] , namely lists of nonsense syllables, which eliminated almost completely the influence of connotations and associations on learning (Müller and Schumann [27] were the first to use not series but just syllables without meaning in 1893-1894) and, in addition, he used quantitative methods to draw his conclusions. Without help and without a laboratory he collected for more than one year in a solitary and monumental effort (being his own and only experimental subject in all his experiments) a long series of experimental explorations in this domain [28] . He used to read aloud every list of syllables in a rather rapid rhythm of 150 units (syllables) per minute. After reaching the end of a list, he would reread from the beginning and continue doing so till he felt capable to recall the whole list without error. If he did not succeed in recalling the list, he just continued rereading it. If he was successful in his attempt to recall the complete list in the correct order two times successively, he made a break of 15 seconds in which he noted the result (the time elapsed for learning the list) and prepared for learning a new list. In his experiments on relearning, the procedure did not differ from the previous study procedure, since Ebbinghaus repeated the same activity to learn the list until he was able to recall the list according to the same criterion, namely, recalling it two times successively in the correct order. It should be noted, that he did not try to recognize or find out, whether a list he was actually studying had already appeared during a previous study phase. The savings that he achieved in terms of learning time or number of learning trials denoted an indicator of the amount of information preserved from the earlier study phase. It was the use of this ingenious dependent variable that represented the experimental transformation of his theoretic considerations on the issue of rote learning. In this way he investigated: (1) the number of repetitions necessary to learn a list (2) the savings as a function of the number of repetitions during prior learning (3) the effects of repeated learning on the savings of relearning (4) but it is in particular his experiments on forgetting as a function of time which were in the center of his initial work on memory. [29] .

Les résultats de ses expériences lui ont fourni le corps de sa thèse d'habilitation qui fut soutenue le 29 avril 1880 à la faculté de philosophie de l'Université Friedrich-Wilhelms à Berlin [cette thèse a été publiée par Traxel (1983)] [30] . Même si les rapports du philosophe Eduard Zeller (1814-1908) et du célèbre physicien Hermann von Helmholtz (1821-1894) furent favorables, ils ont révélé l'attitude ambivalente envers le nouveau type de psychologie qui se développait à l'époque et qui se fondait sur l'expérience et les mathématiques [31] . Non seulement Ebbinghaus rompt avec les méthodes introspectives mais il ouvre aussi un nouveau champ de recherche en apportant la preuve de la possibilité d'atteindre les niveaux supérieurs de comportement humain comme la mémoire et l'apprentissage par le biais de la méthode expérimentale.

The results of his experiments provided him with the data base for his habilitation thesis, which he defended on April 29, 1880 in front of the faculty of philosophy at the Friedrich-Wilhelm University in Berlin [this version of the thesis has been published by Traxel in 1983] [30] . Even though the reports of the philosopher Eduard Zeller (1814-1908) and the famous physicist Hermann von Helmholtz (1821-1894) were very much in favor, they nevertheless revealed that there was an ambiguous attitude towards this new type of psychology which started to be established in that epoch and which was based on experimental methods and on mathematics [31] . Ebbinghaus did not only break with the method of introspection but he opened as well a new research field by demonstrating that it is possible to investigate higher levels of human behavior like memory and learning by the means of the experimental method.

Ebbinghaus, H. (1880/1983). Urmanuskript Über das Gedächtnis (W. Traxel, Ed.) . Passavia-Universitätsverlag : Passau.

La qualité de sa thèse et sa bonne prestation au cours de l'audition lui permirent de donner des cours à partir du semestre d’hiver 1880-1881 en tant que conférencier non salarié (privatdozent) à l'université Friedrich-Wilhelms de Berlin à des étudiants qui devaient payer pour y participer. Cette université, qui fut organisée par Wilhelm von Humboldt (1767-1835) en 1809-1810, était, après Leipzig, où enseignait Wundt, la plus grande institution académique en Allemagne à la fin du XIXe siècle [32] . La Faculté à laquelle appartenait Ebbinghaus était la branche la plus hétérogène de l'université de Berlin. Elle regroupait la philosophie, les sciences naturelles, l'éducation et la pharmacie. La psychologie, spécialement la psychologie expérimentale, était seulement une sous discipline de la philosophie. Durant les quatorze années où il resta à Berlin, il prit en charge divers types d'enseignements, certains de psychologie expérimentale mais d'autres aussi qui étaient loin de ses préoccupations expérimentales (l'histoire de la philosophie et la philosophie de Schopenhauer) mais qui témoignaient de sa culture intellectuelle et de ses divers centres d'intérêt.

Thanks to the quality of his thesis and the accomplished presentation of its defense in front of the faculty he was admitted to teach at the Friedrich-Wilhelm University in Berlin with the beginning of the winter term of 1880-1881. However, because he was a lecturer without salary (Privatdozent), students had to pay to attend his lectures. This university, which had been established by Wilhelm von Humboldt (1767-1835) in 1809-1810 (and was actually renamed into “Humboldt University” in 1946), was the second largest academic institution in Germany by the end of the 19 th century, behind Leipzig (where Wundt had been teaching) [32] . The faculty, to which Ebbinghaus was affiliated, was the most heterogeneous unit of the university. It embraced the disciplines of philosophy, natural sciences, education and pharmacy. Psychology, in particular experimental psychology, was only considered as a sub-discipline of philosophy. During the fourteen years Ebbinghaus remained in Berlin, he was in charge to lecture on different subjects: some were on the topic of experimental psychology, but others were rather distant from his preoccupations (e.g. history of philosophy or the philosophy of Schopenhauer) however, they reveal the breath of his intellectual culture and his various interests.

Publication d’un ouvrage sur la mémoire (1885) [33]

Publication of his book on memory (1885) [33]

Ces activités d'enseignement ne l'éloignèrent pourtant jamais de ses préoccupations expérimentales. C'est entre 1883-1884 qu'il continua ses recherches en reproduisant et en étendant ses expériences sur la mémoire de 1879-1880. Après son mariage en 1884 avec Adele Görlitz (1857-1949) qui lui donna deux filles et deux fils, il publia en 1885 les résultats de ses travaux dans un ouvrage aujourd'hui célèbre, présenté ici en traduction française pour la première fois, et ayant pour titre : "Über das Gedächtnis : Untersuchungen zur Experimentellen Psychologie" (Sur la mémoire : une contribution à la psychologie expérimentale). C'est cet ouvrage [34] , dont il envoya un exemplaire dédicacé à Fechner, qui fera connaître Hermann Ebbinghaus et qui devint immédiatement le détonateur des travaux sur la mémoire et l'apprentissage entrepris en Allemagne, en France et aux Etats-unis [35] . Il est intéressant de souligner que sa monographie sur la mémoire fut traduite en 1913 par deux pédagogues américains A. Ruger et Clara E. Bussenius du "Teachers College" de New York.

Nevertheless, these activities in lecturing did never depart too far from his experimental preoccupations. During the years of 1883-1884 he resumed his studies by replicating and extending his experiments on memory of 1879-1880. After his marriage to Adele Görlitz (1857-1949) in 1884 (who gave birth to two daughters and two sons) he published in 1885 the results of his investigations in his celebrated book "Über das Gedächtnis: Untersuchungen zur Experimentellen Psychologie" (translated into English in the year 1913 as “Memory. A Contribution to Experimental Psychology”). It was this work [34] (of which he sent a dedicated copy to Fechner), through which Hermann Ebbinghaus became known immediately as the proponent of research on memory and learning in Germany and his fame spread soon to the United States and France [35] . It is noteworthy, that the translation of his monograph into English in 1913 was accomplished by two American education scientists, A. Ruger and Clara E. Bussenius from the "Teachers College" in New York .


Dans son ouvrage de 1885, Ebbinghaus complète son travail de 1880 sur bien des points. D’abord, on trouve dès les premières pages de sa monographie une réflexion très approfondie sur le concept de mémoire. Ce chapitre justifie ici pleinement la méthode expérimentale qu’il va utiliser pour mesurer la mémoire (méthode d’économie au réapprentissage). Ensuite, dans toute une série de chapitres, il prend beaucoup de temps et d’espace pour justifier, d’une part, l’utilisation des statistiques (moyennes et indices de variation) en psychologie de la mémoire et, d’autre part, pour informer le lecteur de la méthode de construction de son matériel et des procédures utilisées. Enfin, il complète ses expériences originales de 1880 sur l’apprentissage (effet du nombre de répétitions, de l’espacement des répétitions, etc.) et entreprend d’aborder un sujet d'étude tout à fait original qui n'avait pas du tout été traité dans sa thèse de 1880 : l'étude des lois d'association, en employant la méthode des séries dérivées. En fait, Ebbinghaus tente délibérément ici de tester pour la première fois l'hypothèse de Herbart selon laquelle lorsqu'une série d'items est mémorisée, l'union entre la première représentation et la seconde représentation sera plus fusionnelle qu'entre la première représentation et la troisième. Il montre ainsi qu'il existe une association, non seulement d'un terme au suivant, mais même au-delà de plusieurs termes intermédiaires. La force des connexions augmente aussi en fonction du nombre de répétitions. Si Ebbinghaus n'a jamais tenté de suivre rigoureusement la psychologie de Herbart, ses travaux expérimentaux s'inspirent directement de cette philosophie [36] .

In his book of 1885, Ebbinghaus completed his work of 1880 on many aspects. First of all the introduction of his monograph covers a very profound reflection about the concept of memory. This chapter endorses in a downright way the experimental method he has been using to measure memory performance (savings and relearning). Then, in a series of chapters he uses time and space to justify the usage of statistical indicators (means and indices of dispersion) for the investigation of memory, to explain the way to construct his learning materials as well as the complete procedure of his experiments. Finally, he completes his series of the original experiments of 1880 on learning (effect of the number of repetitions, spacing effects, etc.) and he introduces a new and original study topic (which he did not cover in his thesis of 1880): The study of the laws of association, using the method of derived series. As a matter of fact Ebbinghaus tried to test for the first time the hypothesis advanced by Herbart, namely that in the course of memorizing a series of items, the unification between the first and the second representation is stronger than the unification between the first and the third representation. Thus, he was able to show, that associations are built not only between directly neighboring items in a list but beyond intermediate items of a list. The strength of connections increases furthermore as a function of the number of repetitions. Even though Ebbinghaus did never adhere strictly to the psychology of Herbart, his experimental endeavors display a direct inspiration by this philosophy [36].

French translation (2010) of Ebbinghaus' book (1885) on memory

L’ouvrage d’Ebbinghaus fut très bien accueilli par les critiques [37] . Ebbinghaus a très certainement exercé une puissante influence sur les recherches psychologiques dans le domaine de la mémoire dans les années qui ont suivi la publication de sa monographie [38] et bien au-delà [39] même si ses continuateurs ont délibérément préféré aborder l'étude de la mémoire avec des méthodes classiques (rappel et reconnaissance) qui ne mesurent que l'aspect conscient de l'expression mnésique [40] . Parmi tous les sujets qu'il a traités, les résultats obtenus sur l'apprentissage et l'oubli contribuèrent de manière décisive à encourager de nouvelles recherches dans le domaine de la mémoire. Cependant, si ses travaux ont été le point de départ de nombreuses investigations expérimentales, sa contribution scientifique à l'étude de ce concept fut inexistante par la suite, si l'on excepte celle de 1902 publiée dans son Traité de Psychologie sur les gains au réapprentissage de strophes, et concernèrent principalement d'autres aspects de la vie mentale.

This book by Ebbinghaus was very well recognized by the reviewers [37] . Ebbinghaus has certainly had a very strong impact on the psychological investigation of memory not only in the years following the publication of his monograph [38] but as well beyond [39] despite the fact that later researchers have preferred to approach the study of memory with classical methods (recall and recognition) which however covered only conscious aspects of memory functions [40] . Among all the issues that he has investigated, his results on learning and forgetting have contributed in a conclusive way to encourage new studies in the domain of memory. Yet, despite the stimulating power of his book to trigger numerous experimental studies later on, he himself did not make further scientific contributions to the concept of memory, with the exception of one published 1902 in his “Grundzüge der Psychologie” (could be translated as “Elementary Outline of Psychology”) on the savings of relearning of verses, and other principal aspects of mental functions.

An American Edition (Dover Publications, Inc., 1964)

L'étude expérimentale des sensations, des perceptions et de l’intelligence (1886-1887) et la création du journal de psychologie et de physiologie des organes des sens (1890)

Experimental studies on sensation, perception and intelligence (1886-1887) and the foundation of the Journal of Psychology and the Physiology of the Sensory System (Zeitschrift für Psychologie und Physiologie der Sinnesorgane, 1890)

C'est durant l'année 1886 qu'il fut promu Professeur extraordinaire à l'Université de Berlin avec enfin un salaire régulier et avec l'obligation de donner des cours en psychologie ainsi que des exercices de laboratoire en psychologie expérimentale. Il fonda ainsi à Berlin en 1886, un laboratoire de psychologie expérimentale (celui de Leipzig fut crée par Wundt en 1879 [41] ). Toujours aussi influencé par les travaux de Fechner, Ebbinghaus s'intéressa aux questions psychophysiques. A partir de cette période il entreprit des recherches sur les lois des contrastes de brillance (1887), la loi de Weber (1889), les images consécutives en vision binoculaire (1890), les sentiments de sensation négative (1890) et la perception des couleurs (1893). Ces deux derniers travaux furent d'ailleurs publiés dans la nouvelle revue qu'il venait de fonder en 1890 en collaboration avec Arthur König (1856-1901) : le "Zeitschrift für Psychologie und Physiologie der Sinnesorgane" (Journal de Psychologie et de Physiologie des Organes des Sens" qu'il édita pendant presque 20 ans et que l'on connaît aujourd'hui sous le nom de "Zeitschrift für Psychologie").

In the Year 1886 Ebbinghaus was promoted to the position of an Extraordinary Professor at the Friedrich Wilhelm University in Berlin , and was at last earning a regular salary and given the responsibility to lecture on psychology as well as instructing laboratory exercises in experimental psychology. In the same year he established in Berlin a laboratory of experimental psychology (in Leipzig such a laboratory has been founded by Wundt in 1879 [41] ). Strongly influenced by the work of Fechner, Ebbinghaus was still interested in psychophysical issues. Starting in those times he undertook investigations on the law of (visual) contrasts (1887), on Weber’s law (1889), on consecutive images in binocular vision (1890), on negative values of sensations (Über negative Empfindungswerte, 1890) and on the perception of colors (1893). The latter two articles were actually published in the new journal that he founded in 1890 in collaboration with Arthur König (1856-1901): "Zeitschrift für Psychologie und Physiologie der Sinnesorgane" (“Journal of Psychology and Physiology of the Sensory System"), which he edited for almost 20 years today this journal appears under the name "Zeitschrift für Psychologie".

Cette revue se voulait un organe indépendant qui acceptait des travaux en histoire de la psychologie, en psychologie expérimentale et en méthodologie. Il sut s'entourer de chercheurs de renom comme le toujours influent Helmholtz mais aussi Exner (1846-1926), Hering (1834-1918), Preyer (1842-1897), Müller (1850-1934) et Stumpf (1848-1936) qui avaient en commun le fait d'être des éminents spécialistes sur les questions de psychophysique. Ebbinghaus écrivit dans le premier volume que Fechner pouvait être considéré comme le co-fondateur de cette revue. En fait, le "Journal" rassemblait une coalition de personnalités venant de divers horizons qui voulaient sortir de ou ne pas adhérer à la psychologie de Wilhelm Wundt qui neuf ans auparavant (1881) avait créé sa propre revue, les "Philosophische Studien" (Etudes Philosophiques), dans laquelle il publiait les travaux de ses élèves (en philosophie et en psychologie) ainsi que les résultats expérimentaux obtenus dans son laboratoire de Leipzig.

The purpose of this journal was to be an independent forum for articles in history of psychology, experimental psychology and methodology. Ebbinghaus was able to gather distinguished researchers like the always prominent Helmholtz, but furthermore Exner (1846-1926), Hering (1834-1918), Preyer (1842-1897), Müller (1850-1934) and Stumpf (1848-1936) all of which had in common to be eminent experts on diverse questions of psychophysics. In the editorial of the first volume Ebbinghaus wrote that Fechner could be considered a co-founder of that revue. As a matter of fact, the journal congregated a coalition of personalities with very different point of views, but which did want to depart from or not join the circle of Wilhelm Wundt, who had established his own journal nine years earlier (1881), the "Philosophische Studien" (Philosophical Studies), in which he published the work of his students (in philosophy and in psychology) as well as experimental results obtained in his own laboratory in Leipzig.

C'est certainement l'originalité et la diversité de ses travaux qui inclina Jacob G. Schurman (1854-1942) à proposer à Ebbinghaus de s'établir outre-atlantique dans l'Etat de New York en 1890. Ce philosophe nord-américain, qui semblait connaître personnellement Ebbinghaus pour avoir passé quelques mois à Berlin au début des années 1880, lui demanda en effet de fonder à l'Université Cornell un Institut de psychologie expérimentale. Si la position et le salaire étaient attrayants, des considérations d'ordre personnel influencèrent sa décision de rester à Berlin [42] . D'autres chercheurs allemands à la même époque ont pourtant tenté l'aventure américaine tels Hugo Münsterberg (1863-1916) et Max Meyer (1873-1962).

It was certainly the originality and the diversity of Ebbinghaus’ work which prompted Jacob G. Schurman (1854-1942) to advise him in 1890 to transfer to the New World , specifically to the state of New York . This North-American philosopher seemed to know Ebbinghaus personally because he had been staying in Berlin for a few months at the beginning of the eighteen-eighties. As a matter of fact Schurman asked Ebbinghaus to join Cornell University and to found an institute of experimental psychology there. Even so the position and the salary were appealing, personal matters were accountable for his decision to remain in Berlin [42] . On the other hand, a number of German researchers of the same epoch did try out the American adventure, like Hugo Münsterberg (1863-1916) and Max Meyer (1873-1962).

A partir de cette date (1890), malgré son activité scientifique soutenue et le succès de son enseignement, ses relations avec quelques-uns de ses collègues dont le philosophe Wilhelm Dilthey (1833-1911) et les instances universitaires de la Faculté de Berlin commencèrent à notablement se détériorer. Cette dégradation était surtout liée au fait qu'Ebbinghaus voulait fonder une nouvelle psychologie à laquelle certains de ses contemporains n'étaient pas encore préparés et qui consistait à employer les méthodes expérimentales et les instruments mathématiques déjà utilisés dans les sciences naturelles. N'ayant pas obtenu en été 1893 le poste vacant de professeur ordinaire en philosophie qu'il escomptait (lequel fut par ailleurs attribué à Carl Stumpf qui venait de Munich), il décida de quitter Berlin en acceptant un poste équivalent à Breslau, une université plus petite dans la province prussienne de Silésie, dans la Pologne d'aujourd'hui. Les années passées à Breslau (1894-1905) ont cependant été bénéfiques puisqu'elles lui ont permis d'aborder l'étude d'autres aspects de la vie mentale avec, entre autres, l'étude de l'intelligence : un sujet à la mode à cette époque [43] .

Despite of his ongoing scientific activities and his success as a teacher, from this date (1890) onwards, his relations with some of his colleagues, among them the philosopher Wilhelm Dilthey (1833-1911), but likewise with the academic administration of the Faculty in Berlin started to worsen in a remarkable way. This decline was certainly linked to the fact that Ebbinghaus sought to establish a new approach to psychology for which some of his contemporaries were not yet ready and which consisted in the application of experimental methods and mathematical instruments already used in the natural sciences. When he did not obtain the vacant position as an Ordinary Professor of philosophy in the summer of 1893 as he had envisioned (this position was in fact granted to Carl Stumpf, who had been in Munich before), he decided to leave Berlin by accepting an equivalent position in Breslau, a smaller University in the Prussian county of Silesia, which belongs today to Poland. The years he spent in Breslau (1894-1905) have been very fruitful as they allowed him to start investigating other aspects of mental functions, among them, the study of intelligence, which was at that time a very trendy subject [43] .

Ebbinghaus' famous paper on intelligence (1897)

C'est en 1895, à la demande des échevins de Breslau qui se préoccupaient de mieux distribuer les heures de travail des enfants, qu'Ebbinghaus fut sollicité par les membres de la commission chargée d'étudier la fatigue chez les écoliers dont les cours étaient regroupés le matin de 8h à 13h. Une tentative avait déjà été faite de mesurer la fatigue mentale, en utilisant la méthode psychophysique de discrimination de points, mais Ebbinghaus sentait bien que ce test n'était pas une mesure appropriée. C'est dans ce contexte qu'il inventa la méthode de complètement de phrases (qu'il avait lui-même appelée "méthode des combinaisons") présentée pour la première fois au Congrès International de Psychologie de Berlin en 1896. Selon Woodworth [44] , la méthode de complètement, destinée à apprécier les capacités intellectuelles des écoliers, était probablement le meilleur test d'intelligence disponible à cette époque. Cette épreuve fut d'ailleurs adoptée quelques années plus tard par Binet et Simon (1905) [45] dans leur échelle métrique originale. Si cette très intéressante étude fut à l'origine publiée dans sa propre revue en 1897, la même année une version française abrégée [46] fut éditée par la Revue Scientifique. Ce dernier fait souligne, si besoin en est, la place importante que tenait encore la France dans cette discipline comme en témoignait l'une des premières revues de psychologie expérimentale publiées dans le monde, L'Année Psychologique [47] (1895) et dirigée à l'époque par Alfred Binet (1857-1911). Outre ses études sur l'intelligence, on sait qu'Ebbinghaus travailla aussi à l'Université de Breslau dans le champ de la psychophysique et des illusions d'optique ainsi qu'en témoignent ses communications dans les congrès de psychologie [48] . Pourtant sa véritable activité scientifique lors des années passées dans cette ville fut la rédaction d'ouvrages généraux de psychologie qui eurent à l'époque un succès pour le moins retentissant.

In 1895 on the request of the magistrates of Breslau, who were concerned about how to improve the distribution of lesson hours in schools, Ebbinghaus was approached by members of the committee in charge they pursued to study the fatigue of school children after lesson hours had been re-distributed from 8 am to 1 pm. A first attempt to measure mental fatigue had already been attained, using the psychophysical method of discriminating points. However, Ebbinghaus suspected that this test provided by no means an appropriate measure. In the context of this mandate he invented the method of sentence completion (he himself labeled it "method of combination") which he presented the first time at the International Conference on Psychology at Berlin in 1896. According to Woodworth [44] , the method of completion, which was designed to measure the intellectual capacities of schoolchildren, was probably the best available test of intelligence at that time. Actually, a few years later Binet and Simon (1905) [45] adopted this task in their original metric scale. This very interesting study had been first published in 1897 in his own journal, and in the same year a shortened French version was published in the Revue Scientifique [46] . As this fact underscores, in that epoch, France was a very central and significant location to publish psychological studies, as is furthermore evidenced by the fact that one of the first journals on experimental psychology, L'Année Psychologique [47] appeared there starting in the year 1895 under the direction of Alfred Binet (1857-1911). In addition to his studies on intelligence, while Ebbinghaus was at the University of Breslau , he furthermore working in the field of psychophysics and optical illusions, as is known from his presentations at psychological conferences [48] . However, his bulk of work in the years he spent in this town, were dedicated to the writing of textbooks about general topics of psychology, which were in those times very successful and reputed.

La rédaction d’ouvrages généraux de psychologie (1897-1909)

Authoring General Textbooks on Psychology (1897-1909)

Peu de psychologues savent actuellement qu'Hermann Ebbinghaus a contribué à la diffusion du savoir psychologique en écrivant des ouvrages généraux de psychologie.

Probably only few psychologists know, that Hermann Ebbinghaus did also contribute to the dissemination of psychological knowledge through the writing of general textbooks on psychology.

C'est en 1897 qu'Ebbinghaus commença à publier la première partie du volume I de ses "Grundzüge der Psychologie" (Traité de Psychologie). Dans le premier chapitre (87 p.), l'auteur détermine le point de vue auquel il se place, il discute le but de la psychologie, ses méthodes et ses moyens. Le second chapitre (72 p.) est relatif aux fonctions des centres nerveux. Le troisième chapitre (161 p.) traite des sensations visuelles et auditives. Victor Henri [49] (1872-1940), collaborateur de Binet, soulignait déjà dans une critique de l'ouvrage parue dans L'Année Psychologique (1897, p. 691) que la psychologie développée par Ebbinghaus promettait de devenir d'un volume et d'une qualité égale à la grande psychologie de Wundt. Il fallut attendre 1902 pour que ce volume soit complété [50] . En 1908, Ebbinghaus publia une partie du volume II de son Traité mais sa mort prématurée n'a pas permis qu'il le complète. Leur réimpression a été poursuivie par Ernst Dürr (1878-1913) (troisième éd. du vol. I et seconde éd. du vol. II) et à la mort de ce dernier par Karl Bühler (1879-1963) (quatrième éd. du vol. I) qui ont étendu et complété ses écrits. Il faut savoir que ce traité était considéré à l'époque comme un excellent ouvrage à recommander aux étudiants de langue allemande en psychologie et en philosophie [51] . Titchener [52] jugeait même que ce traité deviendrait à terme beaucoup plus important que les textes de psychologie générale écrits par Wundt ou Brentano. Ebbinghaus devait largement le succès de ce travail à son style clair et attrayant ainsi qu'à sa rigueur d'exposition, qualités qu'on lui reconnaissait aussi dans son enseignement. Quand il eut achevé la première révision de son ouvrage en 1905, il accepta la proposition de l'Université de Halle où il enseigna aussi comme professeur ordinaire.

In 1897 Ebbinghaus started to publish the first part of volume I of his "Grundzüge der Psychologie" (“Elementary Outline of Psychology”). In the first chapter (87 p.), the author exposes his point of view by discussing the purpose of psychology, its methods and its means. The second chapter (72 p.) relates to the functions of the nervous system. The third chapter (161 p.) embraces the sensory system with a primary focus on vision and audition. In a review of this volume appearing in L'Année Psychologique (1897, p. 691), Victor Henri [49] (1872-1940), a collaborator of Binet, emphasized, that the outline of psychology advanced by Ebbinghaus promised to become an equally voluminous and respectable work as the one by Wundt. It lasted however till 1902 that the second part of this volume was completed [50] . In 1908, Ebbinghaus published the first part of volume II of his textbook on Psychology but his premature death did unfortunately inhibit him from completing it. The re-editions of these textbooks had been taken over by Ernst Dürr (1878-1913) (third edition of vol.I and second edition of vol. II) and later by Karl Bühler (1879-1963) (fourth edition of vol. I), who have extended and completed these volumes. In those times, the textbooks were considered as excellent publications which were highly recommended to the German speaking students of psychology and philosophy [51] . Titchener [52] speculated that the textbooks by Ebbinghaus might become even more influential than the texts on general psychology written by Wundt or Brentano. The success of the textbooks was largely due to the clear and attractive writing style of Ebbinghaus and his strictness of exposition, qualities which were attributed to his teaching as well. After having finished the first revision of his work in 1905, he accepted the appointment by the University of Halle , where he was offered an ordinary professorship.

Suite à la rédaction d'un article en 1907 dans la "Kultur der Gegenwart", une revue pluridisciplinaire sur le savoir contemporain dans divers domaines de la connaissance, Ebbinghaus en fit paraître une version plus étoffée sous le titre : "Abriss der Psychologie" (Précis de psychologie) [53] . Après une courte introduction historique et un exposé de la structure du système nerveux, on trouve dans l'ouvrage les questions générales que la psychologie à l'époque ne pouvait se dispenser de poser : rapport de l'âme et du corps, nature de l'âme, et ainsi de suite. Les formations élémentaires (sensations, représentations, sentiments, instinct et volonté) sont ensuite examinées, puis les lois fondamentales de l'activité de l'esprit (attention, mémoire, habitude, fatigue). Les formes complexes (perception, abstraction, langage, pensée, croyance, sentiments) sont enfin abordées et l'ouvrage se termine par le développement des manifestations supérieures de l'esprit dans les faits sociaux, l'art et la religion. Ce manuel de psychologie eut un succès considérable comme en témoignent ses nombreuses rééditions successives corrigées et complétées par Dürr et plus tard par Bühler (1909, 1910, 1911, 1912, 1914, 1919, 1920, 1922, 1932) ainsi que ses traductions américaine (1908) et française (1910) plusieurs fois rééditées. La traduction américaine fut l'œuvre de Max Meyer (1873-1967), professeur de psychologie à l'Université du Missouri, qui souligna dans la préface que la valeur de cet ouvrage résidait surtout dans son côté synthétique et objectif. La traduction française à partir de la seconde édition allemande de 1909 fut l'œuvre de G. Raphael, professeur agrégé d'allemand, et celle de la troisième édition allemande de G. Revault D'Allonnes, directeur adjoint du laboratoire de psychologie pathologique à la clinique des maladies mentales de la Faculté de médecine de Paris et secrétaire de rédaction au Journal de Psychologie Normale et Pathologique fondé en 1904 par Pierre Janet (1859-1947) et Georges Dumas (1866-1946). Le psychologue suisse Jean Larguier des Bancels [54] (1876-1961) résume parfaitement l'impression que l'on peut avoir après la lecture de l'ouvrage lorsqu'il écrit dans L'Année Psychologique en 1910 (p. 494) : "L'abrégé de psychologie présente, au plus haut degré, les qualités d'ordre et de clarté qui appartiennent à l'auteur. Il représente certainement un des meilleurs manuels que nous possédions". Ce manuel d'introduction est en effet aujourd'hui considéré comme un classique à succès de l'époque et contient une locution restée célèbre : "La psychologie a un long passé mais une courte histoire".

In 1907, Ebbinghaus published an article in "Kultur der Gegenwart", a multi-disciplinary journal covering actual topics from different domains of science. Following that he extended it into a much more substantial version with the title "Abriss der Psychologie" (English translation: Psychology - an elementary text-book, 1908) [53] . After a short historical introduction and an exposition of the structure of the nervous system, that work embodies the discussion of general questions which the scientific psychology of that epoch had to embrace: the relation of soul and body, the nature of the soul and so on. Subsequently, basic functions (sensation, imagination, feeling, instinct and willing) and the fundamental laws of mental activities (attention, memory, practice, fatigue) are explicated. The book continues on more complex forms of mental functions (perception, abstraction, language, reasoning, belief, affection) and it ends by illuminating more sophisticated manifestations of the mind in the context of social events, art and religion. This handbook of psychology became a remarkable success as is evident from the numerous re-editions, which were continuously corrected and completed, first by Dürr and later on by Bühler (1909, 1910, 1911, 1912, 1914, 1919, 1920, 1922, 1932) and from the immediate translations into English (1908) and French (1910) with several re-editions. The translation into English was realized by Max Meyer (1873-1967), professor of psychology at the University of Missouri . In the preface he underlined that the value of the book was mainely based in its synthetic and objective standpoint. The French translation of the second German edition of 1909 was accomplished by G. Raphael, Associate Professor of German, and the translation of the third German edition by G. Revault D'Allonnes, who was deputy director of the laboratory for pathological psychology at the clinic for mental illness of the Faculty of medical science in Paris and Co-editor of the Journal de Psychologie Normale et Pathologique established in 1904 by Pierre Janet (1859-1947) and Georges Dumas (1866-1946). The Swiss psychologist Jean Larguier des Bancels [54] (1876-1961) summarized thoroughly the impression of the reading this work in L’Année Psychologique (1910, p. 494): "This outline of psychology displays at the utmost level of quality, the structure and the clarity of ideas by this author. It surely is one of the best handbooks that we hold right now". Today, this handbook can still be considered as a successful standard book of its epoch, in other words, a classic besides, it contains an expression that is still wide-spread and well-known today: "Psychology has a long past but a short history".

C'est à Halle, aussi, qu'Ebbinghaus eut l'idée de commencer une "série de monographies", à laquelle Max Dessoir (1867-1947), Oswald Külpe (1862-1915) et Ernst Meumann (1862-1915) acceptèrent de participer. Il n'eut cependant pas le temps de réaliser cette nouvelle œuvre puisqu'il décéda subitement le 26 février 1909 à la suite d'une pneumonie âgé seulement de 59 ans.

It was also in Halle that Ebbinghaus had the idea to edit a “series of monographs” and for this project Max Dessoir (1867-1947), Oswald Külpe (1862-1915) and Ernst Meumann (1862-1915) accepted to team up. Yet, he did not have the time anymore to realize this new project because of his sudden passing away on February 26, 1909 , due to pneumonia. He was aged 59 years only.

Son originalité, son indépendance de pensée, sa bonne humeur, sa tolérance et son dynamisme, alliés à son style clair d'exposition, faisaient d’Ebbinghaus un orateur très apprécié et un leader dans les congrès nationaux et internationaux auxquels il participait activement (cf. par exemple les Actes du Congrès International de Psychologie qui s'est tenu à Paris en 1900) et ce malgré le nombre relativement restreint de ses publications dans le domaine psychologique. En 1909, Stanley Hall (1844-1924) et Edmund C. Stanford (1859-1924) le convièrent même au 20 e anniversaire de l'Université Clark mais sa disparition prématurée l'a malheureusement empêché de prendre part à cette conférence. Le grand psychologue français Théodule Ribot [55] (1839-1916) dira de lui dans la Revue Philosophique (1909, p. 446) : "L'Allemagne vient de perdre l'un de ses plus éminents psychologues".

His originality, his independence of thought, his humor, his tolerance and his dynamic personality, together with his clear style of exposition, made Ebbinghaus an appreciated speaker and a leader on national and international conferences where he was an active participant (for instance on the International Congress of Psychology which was hold in Paris in 1900) and all this even though the number of his publications in the domain of psychology was rather scarce. In 1909, Stanley Hall (1844-1924) and Edmund C. Stanford (1859-1924) invited him to participate on the 20 th anniversary of Clark University , however, his premature death unfortunately prevented his participation on that event. The great French psychologist Théodule Ribot [55] (1839-1916) wrote about him in the “Revue Philosophique” (1909, p. 446): "L'Allemagne vient de perdre l'un de ses plus éminents psychologues" ( Germany has lost one of its most eminent psychologists).

Si la lecture de son œuvre nous convainc qu'il ne peut en aucun cas être rattaché à une école de pensée, on peut cependant affirmer que tout au long de sa vie académique Ebbinghaus sera influencé par les idées de Fechner [56] . L'importance qu'Ebbinghaus accordait à Fechner fut clairement exprimée à maintes reprises dans ses écrits et on en trouve une belle formulation en forme de dédicace dans son Traité de Psychologie : "Je vous dois tout". Cette influence est cependant surtout prégnante dans sa monographie sur la mémoire par l'application de la méthode expérimentale à l’étude des processus supérieurs de l’esprit. Il était ainsi un original et un pionnier dans l'étude des processus mentaux supérieurs comme l'ont aussi montré ses études sur l'intelligence. Malgré le succès de ses manuels de psychologie générale, c'est sans nul doute la monographie d'Ebbinghaus sur la mémoire qui reste aujourd'hui son œuvre maîtresse.

Even if the reading of his oeuvre leads at any rate to the conclusion that Ebbinghaus cannot be associated with any school of thought, it is nevertheless evident that through his whole academic life he has been strongly shaped by the ideas of Fechner [56] . The importance that Ebbinghaus himself attributed to Fechner’s influence has been clearly expressed frequently in his writings. Yet, most delightfully and poetically it is phrased in the dedication of his textbook “ Grundzüge der Psychologie” :

Dem Andenken GUSTAV THEODOR FECHNER’S gewidmet (in memory of GUSTAV THEODOR FECHNER):

Betrachtet ich den Fleiß, den ich verwendet,

Sah ich die Züge meiner Feder an,

So konnt‘ ich sagen, dieses Buch ist mein.

Doch überdenk‘ ich’s recht, da es vollendet,

Woher mir alles kam, wohin es zielt,

Erkenn ich wohl, ich hab‘ es nur von Euch.

Considering the diligence, I have invested,

Or seeing the strokes of my handwriting,

I would say, this book is my creation.

Yet, reconsidering properly, after its completion,

From where everything did come, where to it is

I acknowledge frankly, I owe it to You.

The influence of Fechner is particularly apparent in his monograph on memory by applying the experimental method to the study of the mind. Thus, he was a unique and original pioneer for the study of higher mental processes, as his studies on intelligence have additionally demonstrated.

Despite the success of his textbooks on general psychology, his monograph on memory is nowadays with no doubt the masterpiece, he is remembered for: Every scholar of psychology knows him for his learning of countless lists of nonsense syllables! These efforts of his were not in vain but they conveyed an extremely meaningful contribution, not only to the understanding of human memory but to the launching of an experimental approach to psychological questions and thus, to open the way for psychology to become a science of its own.

[1] Ce texte est une reprise partielle, aménagée et complétée d’un article déjà publié sur le sujet : Nicolas, S. (1994). Hermann Ebbinghaus (1850-1909) : La vie et l’œuvre d’un grand psychologue expérimentaliste. Swiss Journal of Psychology, 53, 5-12. Nous remercions la Revue suisse de psychologie pour nous avoir donné l’autorisation de reproduire cet article. This text is an adapted and completed version on an earlier publication on the same subject: Nicolas, S. (1994). Hermann Ebbinghaus (1850-1909): La vie et l’œuvre d’un grand psychologue expérimentaliste. Swiss Journal of Psychology , 53, 5-12. We would like to thank the Swiss Journal of Psychology for its permission to use this article.

[2] See Traxel, W., & Gundlach, H. (1986) (Eds.). Ebbinghaus - Studien 1 . Passavia-Universitätsverlag : Passau.

[3] Dallenbach, K. M. (1954). Ebbinghaus' bibliography. American Psychologist, 9, 265-266.

[4] Gorfein, D.S. & Hoffman, R.R. (1987). Memory and Learning : The Ebbinghaus Centenial Conference . Hillsdale , New Jersey : Lawrence Erlbaum Associates. ― Klix, F., & Hagendorf, H. (1986) (Eds.). Human Memory Cognitive Capabilities : Mechanisms and Performances (part A). Amsterdam : North-Holland. ― Roediger, H. L. (1985a). Special section : Ebbinghaus symposium. Journal of Experimental Psychology : Learning, Memory and Cognition, 11, 413-500.

[5] Caparros, A., & Anguera, B. (1986). Ebbinghaus y la tradicion functionalista. Revista de Historia de la Psicologia, 7, 11-27

[6] Nicolas, S. (2002). La fondation de la psychophysique de Fechner : Des présupposés métaphysiques aux écrits scientifiques de Weber. L'Année Psychologique, 102, 255-298.

[7] Sprung, L. & Sprung, H. (1986). Hermann Ebbinghaus : Life, work and impact in the history of psychology. In F. Klix & H. Hagendorf (Eds.), Human Memory Cognitive Capabilities : Mechanisms and Performances (part A). Amsterdam : North-Holland. ― Traxel, W. (1987) (Ed.). Ebbinghaus-Studien 2. Passavia-Universitäts-verlag : Passau.

[8] Pour une étude de la réception en France et en Allemagne de cet ouvrage : Nicolas, S., & Fedi, L. (2008). Un débat sur l’inconscient avant Freud. La réception de Eduard von Hartmann chez les psychologues et philosophes français. Paris : L’Harmattan. For a survey of the reception of this work in France and Germany , see: Nicolas, S., & Fedi, L. (2008). Un débat sur l’inconscient avant Freud. La réception de Eduard von Hartmann chez les psychologues et philosophes français . Paris : L’Harmattan.

[9] For a French edition : Hartmann, E. von (2008). Philosophie de l’inconscient (2 vol.). Paris : L’Harmattan. For the first English translation: Hartmann, E. von (1884). Philosophy of the unconscious. New York : Macmillan.

[10] Segura, M. C. G., & Caparros, A. (1987). La recepcion de Fechner en Ebbinghaus. Revista de Historia de la Psicologia, 8, 255-271.

[11] Boring, E. G. (1957). A History of Experimental Psychology. New York : Appleton-Century-Croft. Page 387.

[12] Shakow, D. (1930). Hermann Ebbinghaus. American Journal of Psychology, 62, 505-518. Page 510.

[13] Hoffman, R. R., Bamberg, M., Bringman, W., & Klein, R. (1987). Some historical observations on Ebbinghaus. In D. S Gorfein & R. R. Hoffman (Eds.), Memory and Learning : The Ebbinghaus Centenial Conference. Hillsdale , New Jersey : Lawrence Erlbaum Associates. ― Traxel, W., & Gundlach, H. (1986) (Eds.). Ebbinghaus - Studien 1 . Passavia-Universitätsverlag : Passau.

[14] Jaensch, E.R. (1909). Hermann Ebbinghaus. Zeitschrift für Psychologie, 51, I-VII.

[15] Traxel, W. (1985). Hermann Ebbinghaus : In memoriam. History of Psychology Newsletter , 17, 37-41.

[16] Traxel, W. (1987) (Ed.). Ebbinghaus-Studien 2. Passavia-Universitäts-verlag : Passau. — Traxel, W., & Gundlach, H. (1986) (Eds.). Ebbinghaus - Studien 1. Passavia-Universitätsverlag : Passau.

[17] Boring, E. G. (1957). A History of Experimental Psychology. New York : Appleton-Century-Croft. ― Roediger, H. L. (1985b). Remembering Ebbinghaus. Contemporary Psychology, 30, 519-523.

[18] Hoffman, R. R., Bamberg, M., Bringman, W., & Klein, R. (1987). Some historical observations on Ebbinghaus. In D. S Gorfein & R. R. Hoffman (Eds.), Memory and Learning : The Ebbinghaus Centenial Conference. Hillsdale , New Jersey : Lawrence Erlbaum Associates.

[19] Shakow, D. (1930). Hermann Ebbinghaus. American Journal of Psychology, 62, 505-518.

[20] Bringmann, W. G., & Bringmann, N. J. (1986b). Hermann Ebbinghaus 1875-1879 : The missing years. In W. Traxel & H. Gundlach (Eds.), Ebbinghaus-Studien 1 (pp. 59-100). Passau : Passavia Universitätsverlag.

[21] Nicolas, S. (2000). La mémoire humaine . Paris : L’Harmattan.

[22] Nicolas, S. (1992). Hermann Ebbinghaus et l'étude expérimentale de la mémoire humaine. L’Année Psychologique, 92, 527-544.

[23] Boring, E. G. (1957). A History of Experimental Psychology. New York : Appleton-Century-Croft. ― Roediger, H. L. (1985b). Remembering Ebbinghaus. Contemporary Psychology, 30, 519-523.

[24] Cette conception de la mémoire était à l'époque défendue par Ewald Hering (1870) dont Ebbinghaus avait lu avec attention les écrits. Hering, E. (1870). Über das Gedächtnis als eine allgemeine Funktion der organisierten Materie. Almanach. Oesterreichische Akademie der Wissenschaften, 20, 253-278. This conception of memory had been advanced by Ewald Hering (1870) who’s writings Ebbinghaus had been reading with high interest. Hering, E. (1870). Über das Gedächtnis als eine allgemeine Funktion der organisierten Materie. Almanach. Oesterreichische Akademie der Wissenschaften, 20, 253-278.

[26] Heller, D. (1986). On natural memory. In F. Klix & H. Hagendorf (1986) (Eds.). Human Memory Cognitive Capabilities : Mechanisms and Performances (part A) (pp. 161-169). Amsterdam : North-Holland.

[27] Müller, G. E., & Schumann, F. (1894). Experimentelle Beiträge zur Untersuchung des Gedächtnisses. Zeitschrift für Psychologie und Physiologie der Sinneorgane , 5, 81-190 257-339.

[28] L'objectif de son premier travail fut d'étudier la mémoire autrement qu'en utilisant la méthode introspective basée sur l'examen de conscience Fechner et bien d'autres après lui avaient utilisé l'expérimentation dans le domaine des sensations élémentaires. Il écrit à propos de Herbart dans son travail de 1880 : "On se souvient des efforts de Herbart pour établir des lois mathématiques sur les événements psychiques. Il ne parvint ni à vérifier les hypothèses de ses expériences directement par des observations, ni à prouver par des mesures réelles la concordance des résultats obtenus avec les faits. Ainsi sa tentative est restée une pure spéculation théorique. Mais cela n'aurait même pas été pensable s'il ne s'était pas basé sur les caractéristiques des événements psychiques, pouvant être considérés comme appartenant à la catégorie des événements mesurables. (. ) Tout l'intérêt de cette recherche se concentre sur la "force" des représentations par rapport à la conscience, l'énergie particulière ou la vivacité avec laquelle elles sont représentées." (1880, p. 4) (. ) Je ne sais pas si, et de quelle manière, il sera un jour possible d'introduire dans le cercle des examens pratiques cette force des représentations de Herbart. La vivacité des images de souvenir me semble en revanche être moins inaccessible, et la persévérance dans une voie pourtant de longue haleine, amènera peut-être un jour à des conclusions exactes à son sujet". (1880, p. 9).

The purpose of his first work was to study memory in a different way than by the use of the introspective method which was restricted on the examination of conscious processes Fechner and others after him have applied the experimental method in the domain of the elementary senses. In his work of 1880 he wrote with reference to Herbart: " One might remember the efforts by Herbart to establish the mathematical laws on psychic events. He did not attain, neither to verify the hypotheses in his experimentations directly by observation, nor to prove with physical measures the correspondence of the results obtained with the facts. Thus, his approach remained an entirely theoretical speculation. However, this would not even have been conceivable, if he did not base himself on characteristics of psychic events, which could be considered as measurable events. (. ) The whole interest of this investigation is focused on the "strength" of the representations in relation to consciousness, the particular energy or vividness, with which they are stored " (1880, p. 4). (. ) " I do not know, whether, and in which way, it might become possible one day to apply a set of practical examinations to assess this strength of the representations as depicted by Herbart. The intensity of memory representations on the other hand appears to me less inaccessible, and perseverance on an unquestionably long track may finally lead us to exact conclusions on the issue " (1880, p. 9).

[29] Plusieurs théories de l'oubli existaient à l'époque. Selon la première théorie, défendue à l'époque par Joseph Delboeuf (1831-1896), il n'y a pas évanouissement mais seulement une inaccessibilité temporaire des souvenirs (cf., Nicolas, 1995). Selon la seconde théorie, soutenue à l'époque par Hermann Lotze (1817-1881), l'oubli consiste en un fractionnement des souvenirs en composantes élémentaires. Selon la troisième théorie, soutenue par Herbart et ses continuateurs dont Theodor Waitz (1821-1864) était à l'époque le représentant le plus connu, l'oubli consiste en un obscurcissement graduel des souvenirs anciens dû à l'arrivée de nouveaux souvenirs. Il examina l'influence du temps en prenant en compte les modalités suivantes : 1/4 d'heure, 1 heure, 8 1/2 heures, 1, 2, 6 et 31 jours. Ces recherches sur l'oubli ont été réalisées par Ebbinghaus pendant l'année 1879-1880 et ont été reproduites dans le chapitre VII de son fameux ouvrage de 1885 (Ebbinghaus, 1885). La technique utilisée consistait en l'apprentissage 163 séries de 13 syllabes. L'apprentissage se poursuivait jusqu'au critère de deux récitations sans erreur des séries en question. Le réapprentissage était réalisé dans les mêmes conditions il se produisait à l'une des sept périodes de temps citées ci-dessus. Les résultats obtenus en termes d'économie au réapprentissage ont été simulés par Ebbinghaus lui-même en une formule mathématique de type logarithmique (oubli rapide dans les premières minutes et déclin progressif de la mémoire par la suite). La mathématisation des résultats était un pré-requis indispensable à l'élévation de la psychologie comme science naturelle il reproduisait ainsi la tentative de G. T. Fechner (1801-1887) qui avait donné une formule logarithmique de la sensation en rapport avec la stimulation.

Several theories about forgetting had been advanced at that time. According to the first theory fostered by Joseph Delboeuf (1831-1896), there is no vanishing but just a temporary inaccessibility of memories (cf., Nicolas, 1995). A second theory upheld by Hermann Lotze (1817-1881), postulated that forgetting was due to the segmentation of memories into its elementary components. The third theory forwarded by Herbart and his followers, among them Theodor Waitz (1821-1864) was at that time the most prominent one: forgetting entails a gradual obscuring of old memories due to the arrival of memories for new experiences. Ebbinghaus examined the influence of time by varying the time delay as follows: 20 minutes, 1 hour, 8 hours, 1, 2, 6 and 31 days. These investigations on forgetting were carried out during 1879-1880 and they are described in chapter 7 of his well-known of 1885 (Ebbinghaus, 1885). His procedure was to learn 163 lists of 13 syllables in the first place. Learning was accomplished after two successful and errorless recalls of the lists in question. Then, relearning was carried out under the same conditions, in one of the seven time lag conditions as described above. The results in terms of savings for relearning were modeled by Ebbinghaus himself using a mathematical formula of logarithmic type (rapid forgetting at short time lags and continuously decreasing forgetting over the long time lags). The quantification of results was an indispensable prerequisite to endorse psychology as a natural science in this manner he mimicked the tryouts of G. T. Fechner (1801-1887) who developed a logarithmic formula in order to model the relation between sensation and stimulation.

[30] Ebbinghaus, H. (1880/1983). Urmanuskript Über das Gedächtnis. Passavia-Universitätsverlag : Passau.

[31] Faisant partie de son jury, le physiologiste Hermann von Helmholtz écrit dans son rapport (Bringmann & Bringmann, 1986a) : "C ette étude expérimentale a été intelligemment réalisée, sérieusement et patiemment conduite. La discussion des résultats expérimentaux montre un bon jugement et une solide connaissance des mathématiques. Les résultats ne sont pas très impressionnants, mais on ne pouvait pas le savoir avant d'avoir réalisé ce travail expérimental. Cette thèse m'a fait une bonne impression l'auteur m'a fait l'impression d'un esprit brillant, qui peut dire de manière brève et réfléchie ce qui est réellement important ". Si Helmholtz avait été déçu par les résultats, il faut reconnaître qu'il ouvrait un nouveau champ de recherches spécifique à la psychologie et non importé d'une autre science (la perception et la psychophysique sensorielles ont d'abord été étudiées par des physiologistes et des physiciens, les temps de réaction par les astronomes). Les niveaux supérieurs de comportement pouvaient être atteints par le biais de la méthode expérimentale, ce que contestaient à l'époque le principal représentant de la psychologie : Wilhelm Wundt.

Being a member of the habilitation committee, the physiologist Hermann von Helmholtz wrote in his report (Bringmann & Bringmann, 1986a): "This experimental study has been accomplished in an intelligent way, and conducted seriously and passionately. The discussion of the experimental results uncovers an excellent capacity of judgment and fundamental knowledge of mathematics. The results are not very impressive, but this was not to be known ahead of conducting this experimental work. . This thesis has left me with a good impression the author has convinced me to be a brilliant mind, competent to express the essential issues in a brief and well considered way ". If Helmholtz was disappointed about the results, it has to be acknowledged that he opened a new and specified research field to psychology, which was not introduced from another science (perception and sensory psychophysics have first been studied by physiologists and physicists, reaction times by astronomers). Higher levels of behavior were now open to investigation through the application of the experimental method, a fact that had been disputed by the leading representative of psychology of the time: Wilhelm Wundt.

[32] Pour une présentation des universités allemandes de l'époque : Decaisne, G. (1876). Les universités de l'Europe en 1876 : Les Universités allemandes. Revue Scientifique , 10, 266-271. For an account of German Universities of the time: Decaisne, G. (1876). Les universités de l'Europe en 1876 : Les Universités allemandes. Revue Scientifique, 10, 266-271.

[33] Ebbinghaus, H. (1885). Über das Gedächtnis : Untersuchungen zur Experimentellen Psychologie. Leipzig : Duncker & Humblot (traduction américaine par H. A. Ruger & C. E. Bussenius (1913/1964), Memory : A contribution to Experimental Psychology. New York : Dover Publications).

[34] Nicolas, S. (1992). Hermann Ebbinghaus et l'étude expérimentale de la mémoire humaine. L’Année Psychologique, 92, 527-544.

[35] Pour une anthologie de textes fondamentaux de la fin du XIX e siècle sur la mémoire en traduction française : Nicolas, S., & Piolino, P. (2012). La mesure de la mémoire humaine : premiers travaux scientifiques. Paris : L’Harmattan (à paraître). For a compilation of basic texts on memory at the end of the 19 th century in French translation, see: Nicolas, S., & Piolino, P. (2012). La mesure de la mémoire humaine : premiers travaux scientifiques . Paris : L’Harmattan (in press).

[36] Cf. Nicolas, S. (2005). L’influence de la psychologie de Herbart sur l’étude de la mémoire par Ebbinghaus. In J. C. Dupont (Ed.), Histoires de la mémoire (pp. 173-185). Paris : Vuibert.

[37] Jacobs, J. (1885). Review of Ebbinghaus : Über das Gedächtnis. Mind, 10, 454-459. — James, W. (1885). Experiments in memory. Science, 6, 198-199

[38] Schacter, D. L. (1982). Stranger behind the engram : Theories of memory and psychology of science. Hillsdale, New Jersey : Lawrence Erlbaum Associates.

[39] Slamecka, N. J. (1985a). Ebbinghaus : Some associations. Journal of Experimental Psychology : Learning, Memory and Cognition, 11, 414-435. ― Slamecka, N. J. (1985b). Ebbinghaus : Some rejoinders. Journal of Experimental Psychology : Learning, Memory and Cognition, 11, 496-500.

[40] For a discussion : Nicolas, S. (1992). Hermann Ebbinghaus et l'étude expérimentale de la mémoire humaine. L’Année Psychologique, 92, 527-544.

[41] Pour une présentation du laboratoire de Wundt à cette époque : Nicolas, S., Gyselinck, V., Murray, D. J., & Bandomir, C. A. (2002). French descriptions of Wundt's laboratory in Leipzig in 1886. Psychological Research, 66, 208-214. — Nicolas, S. (2005). Wundt et la fondation en 1879 de son laboratoire. Histoire documentaire de la création et du développement de l’Institut de psychologie expérimentale de Leipzig. L’Année Psychologique, 105, 133-170.

For a presentation of the laboratory of Wundt, see: Nicolas, S., Gyselinck, V., Murray, D. J., & Bandomir, C. A. (2002). French descriptions of Wundt's laboratory in Leipzig in 1886. Psychological Research, 66, 208-214. — Nicolas, S. (2005). Wundt et la fondation en 1879 de son laboratoire. Histoire documentaire de la création et du développement de l’Institut de psychologie expérimentale de Leipzig. L’Année Psychologique , 105, 133-170.

[42] Bringmann, W. G., & Bringmann, N. J. (1986a). Ebbinghaus and the new world. Revista de Historia de la Psicologia , 7, 71-80. — Traxel, W. (1987) (Ed.). Ebbinghaus-Studien 2. Passavia-Universitäts-verlag : Passau.

[43] Cf. Nicolas, S., & Andrieu, B. (Eds.) (2005). La mesure de l’intelligence. Paris : L’Harmattan. - Fuchs, A. H. (1997). Ebbinghaus's contributions to psychology after 1885. American Journal of Psychology, 110, 621-633.

[44] Woodworth, R. S. (1909). Hermann Ebbinghaus. Journal of Philosophy, Psychology and Scientific Methods, 6, 253-256.

[45] Binet, A., & Simon, Th. (2004). L’élaboration du premier test d’intelligence (1904-1905) (Œuvres choisies II). Paris : L’Harmattan.

[46] Ebbinghaus, H. (1897). Une nouvelle méthode d'appréciation des capacités intellectuelles. Revue Scientifique, 8, 424-430.

[47] Nicolas, S., Segui, J., & Ferrand, L. (2000a). L'Année Psychologique : History of the founding of a centenarian journal. History of Psychology, 3, 44-61. — Nicolas, S., Segui, J., & Ferrand, L. (2000b). Les premières revues de psychologie : La place de L'Année Psychologique. L'Année Psychologique, 100, 71-110.

[48] Sprung, L. & Sprung, H. (1986). Hermann Ebbinghaus : Life, work and impact in the history of psychology. In F. Klix & H. Hagendorf (Eds.), Human Memory Cognitive Capabilities : Mechanisms and Performances (part A). Amsterdam : North-Holland.

[49] Nicolas, S. (1994). Qui était Victor Henri (1872-1940) ? L'Année Psychologique, 94, 385-402.

[50] For a French critical review : Foucault, M. (1903). Revue de l'ouvrage "Grundzüge der Psychologie" par Ebbinghaus. Revue Philosophique, 55, 329-341.

[51] Cunningham, J. L. (1986). A comparison of "Psychology : An Elementary Textbook" by Hermann Ebbinghaus with modern introductory textbooks. Revista de Historia de la Psicologia, 7, 59-70.

[52] Titchener, E.B. (1910). The past decade in experimental psychology. American Journal of Psychology, 21, 404-421.

[53] Ebbinghaus, H. (1908). Abriss der Psychologie . Berlin : De Gruyter (traduction française par G. Raphel (1912), Précis de Psychologie. Paris : Alcan).

[54] Nicolas, S. (2001). Le collaborateur suisse d'Alfred Binet : Jean Larguier des Bancels. Cahiers Alfred Binet , n° 668, 95-109.

[55] Nicolas, S., & Murray, D. (1999). Théodule Ribot (1839-1916), founder of French psychology : A biographical introduction. History of Psychology , 2, 277-301. — Nicolas, S. (2005). Théodule Ribot : philosophe breton fondateur de la psychologie française. Paris : L’Harmattan.

[56] Traxel, W. (1987) (Ed.). Ebbinghaus-Studien 2. Passavia-Universitäts-verlag : Passau.


Ebbinghaus like model for retention of details from experience - Psychology

In 1885, according to this article in Wikipedia,

Hermann Ebbinghaus discovered that memory decays exponentially. The
formula he came up with for modeling forgetting curve was

Where R is memory retention, S is the relative strength of the memory,
and t is time.

I have a couple of questions about this formula.

1. What are the units for S?

This formula is a variation of the standard exponential half-life
decay function

In that formula, h is in the same units as t (time), so I assume that
S is also in the same units as t (time).

2. What are the units for R?

In the half-life formula, y and y0 are usually mass units (grams).
Since there is no R0, I am assuming that it is "1".

This means that R goes from 1 to 0, which suggests that it's a
probability. Is it the probability of recall?

Note that this formula is only a qualitative approximation to the decay
of memories. It provides little (if any) insight to the mechanism by
which memories may 'decay' and I doubt that
a) it is applicable over a wide range of t,
b) matches statistical data more than very approximately at best.

Also, it is a little self-fulfilling as there appears to be no way to
independantly estimate S other than by recording the R returned by
fitting the equation to some specific set of data. What I am saying here
is that while t is clearly 'time', and R is clearly some statistical
measure of how much 'memory is retained' after time t, it is not clear
that S represents 'strength of memory' in any real sense of the meaning
of S. Might be better to call S the 'memory decay constant' or 'memory
half-life'.

The probability of recall would be a reasonable guess, but without
access to Ebbinghaus' data it wouild be impossible to say for sure.

While I'm no expert, it is my impression that the formula is a fairly
good approximation, at least after new material has been learned.
Ebbinghaus did his research using nonsense words, but I believe others
have extended that to more general data.

There are those who disagree.

If you click on the first reference in the wiki article - you get a 1913
translation of Ebbinghaus' work. There should be enough information
there to answer your questions.

Well, maybe for someone with better statistics skills. One problem
is that most of the charts are poorly labeled or completely unlabeled.
It was often not clear to be what the independent and dependant
variables were.

Finally, the formula above attrobuted to Ebbinghaus is not in this
paper at all!

In Section 29: Discussion of results, the discussion seems to focus on
a binary recall/norecall (what I think he calls "production"). I am
assuming that the actual measure is the point at which the memory
slips below the recall strength.

In short, I believe that R *is* recall probabiity. If you disagree,
please point me to the relevant section of the paper.

I had a closer look at the paper and believe that the error could be in
the wikipedia article. The table just above the heading 'Section 29', in
chapter 7 appears to summarise his data - note that I haven't checked
that it is a valid summary but, assuming it is, it predicts a very
different behaviour from the wiki article.

= exp(-t/s),
whereas a simple fit to the data suggests
b) R

= Ao*t^(-b)
for appropriately chosen Ro,s,Ao,b, over a significant range of t (and
Ebberhaus comes to a similar conclusion about 20 lines down from the
table).

The two behaviours are very different.
a) claims that for any set of learned data, if (for example) you forget
10% on the first day, then you will forget 10% of what is left on the
second day, 10% of what is still left on the third day, another 10% on
the fourth day, etc.
b) claims that for the same set of data, if (for example) you forget
10% on the first day, you might forget another 10% of the total in the
next 2 days, another 10% of the total in the next 4 days, 10% in the
next 8 days, etc..

My guess is that someone, either the writer of the qwiki or the
reference they used to write it, misunderstood or misinterpreted the
papoer and data, or didnt really understand the nature of exponentials
and logarithms. Note that if formula b) is approximately correct then it
is also approximately true that exp(R)

= k*t (for some constant k), so
there _is_ an exponential relationship between memory and time, but just
not of the nature shown by the wiki.

As a physicist (and I have to admit I have no background in psychology
or teh theory of brain function), I always like to check a proposed
formula by looking at what it suggests in real life. If you look at the
comment near the bottom of the wiki that states "In a typical schoolbook
application (e.g. learning word pairs), most students remember only 10%
after 3?6 days (depending on the material)", the (presumably incorrect
?) wiki formula suggests that on the same test the students would only
remember 1% in 6-12 days, and 0.1% in 9-18 days, which might be a little
far-fetched. Whereas formula b) (Ebberhaus' and mine from fitting the
data) might suggest that teh 1% retention might be after 30-60 days (for
example) and the 0.1% retention after a year or two - this 'feels' a bit
more reasonable when compared with my personal experience.

= exp(-t/s),
whereas a simple fit to the data suggests
b) R

= Ao*t^(-b)
for appropriately chosen Ro,s,Ao,b, over a significant range of t (and
Ebberhaus comes to a similar conclusion about 20 lines down from the
table).
The two behaviours are very different.
a) claims that for any set of learned data, if (for example) you forget
10% on the first day, then you will forget 10% of what is left on the
second day, 10% of what is still left on the third day, another 10% on
the fourth day, etc.
b) claims that for the same set of data, if (for example) you forget
10% on the first day, you might forget another 10% of the total in the
next 2 days, another 10% of the total in the next 4 days, 10% in the
next 8 days, etc..
My guess is that someone, either the writer of the qwiki or the
reference they used to write it, misunderstood or misinterpreted the
papoer and data, or didnt really understand the nature of exponentials
and logarithms. Note that if formula b) is approximately correct then it
is also approximately true that exp(R)

= k*t (for some constant k), so
there _is_ an exponential relationship between memory and time, but just
not of the nature shown by the wiki.

What you say makes intuitive sense. Thanks for taking the time to
check it out.

Do you have any interest is doing some consulting on this and related
topics? I have some work I need to do and my math skills are not up to
the task.

= exp(-t/s),
whereas a simple fit to the data suggests
b) R

= Ao*t^(-b)
for appropriately chosen Ro,s,Ao,b, over a significant range of t (and
Ebberhaus comes to a similar conclusion about 20 lines down from the
table).
The two behaviours are very different.
a) claims that for any set of learned data, if (for example) you forget
10% on the first day, then you will forget 10% of what is left on the
second day, 10% of what is still left on the third day, another 10% on
the fourth day, etc.
b) claims that for the same set of data, if (for example) you forget
10% on the first day, you might forget another 10% of the total in the
next 2 days, another 10% of the total in the next 4 days, 10% in the
next 8 days, etc..
My guess is that someone, either the writer of the qwiki or the
reference they used to write it, misunderstood or misinterpreted the
papoer and data, or didnt really understand the nature of exponentials
and logarithms. Note that if formula b) is approximately correct then it
is also approximately true that exp(R)

= k*t (for some constant k), so
there _is_ an exponential relationship between memory and time, but just
not of the nature shown by the wiki.

Glad to have been of help.

Could be interested if there is some small compensation for my time. You
could contact me privately by deleting the 'nospam' (and one of the '.')
from my e-mail address.


The Internal Assessment

  • Relevant Theory: The multi-store model of memory
  • Tip 1: Simplify the IV to two conditions to make the inferential statistics easier.
  • Tip 2: To conduct the inferential statistics, you will need two conditions (mean scores) to compare for onedependent variable. You should therefore focus on the primacy orthe recency effect. Choose one (Note: one of them is much better than the other to choose because there are different results in each condition – see the graph above to make your decision).
  • Tip 3: You will need two average scores to compare. You will need to operationally define what the primacy or recency is in your experiment. For example, if you’re doing recency only, is this the last word in the sequence, the last two words, the last quarter, one third, etc. You could base your decision on the graph above.
  • Tip 4: If you decide against using this study for your IA, check out this blog post instead: Key Studies for the IA

Travis Dixon is an IB Psychology teacher, author, workshop leader, examiner and IA moderator.


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