EBBINGHAUS, HERMANN (1850-1909)

Hermann Ebbinghaus was the founder of the experimental psychology of memory. He laid the foundation for the scientific study of memory in a monograph titled Über das Gedächtnis (1885), translated into English in 1913 under the title Memory: A Contribution to Experimental Psychology.

Life

Ebbinghaus was born on January 23, 1850, at Barmen, near Bonn, Germany. His father was a well-to-do merchant. He studied languages and philosophy at the University of Bonn. He served in the army during the Franco-Prussian War of 1870-1871, and upon returning to the university completed his doctoral dissertation in 1873. He then spent some five years traveling in France and England. He began his research on memory at Berlin in 1878, spending more than a year on the initial set of experiments. Upon completing these studies he became a private lecturer at the University of Berlin in 1880, and he continued his studies of memory. He repeated many of the original experiments from 1879-1880 in 1883-1884 and added new ones. He published the report on both series in his 1885 monograph.

Ebbinghaus's life after he published his epochmaking study was active and productive. He was appointed a professor at the University of Berlin in 1886, remaining there until 1894, when he moved to the University of Breslau. He stayed at Breslau for eleven years and then accepted an appointment at the University of Halle. Over the years he became a prominent and respected member of the new scientific discipline of experimental psychology. A major source of his renown lay in his textbook of general psychology, Grundzüge der Psychologie (1897), which became the most widely read psychology text in Germany. Ebbinghaus died of pneumonia at Halle on February 26, 1909.

Ebbinghaus's Approach to Memory

Before Ebbinghaus, the study of memory consisted of philosophical armchair speculation concerning remembering and forgetting in everyday life, and clinical observations of patients with memory disorders. The philosophical approach of the day is reflected in William James's Principles of Psychology (1890);. the clinical approach is illustrated by the work of Théodule Ribot. Both lines of thought produced many insights into the nature and workings of normal and impaired memory. However, there were also curious gaps; not surprisingly, the contemporary thinkers were unaware of many of them. One widely held view, for instance, maintained that memory could not be studied by strict scientific methods. Although methods of science had been applied to the "lower" mental processes, such as sensation and perception, under the general rubric of psychophysics, the "higher" mental processes such as memory were regarded as being beyond the pale of such methods. Another tacit idea of the time was that remembering and forgetting occur in an all-or-nothing fashion: A person either does or does not remember a fact, a thought, a name, and the like. The possibility that nonrecoverable mental contents could exist at different levels of strength was discussed neither by philosophers nor by students of memory pathology.

Ebbinghaus's work changed all that. In his now-classic monograph he introduced the general approach to the study and measurement of learning and memory by psychological means, outlined the appropriate methodology, and reported a number of experiments illustrating the power of his methods.

The general strategy that Ebbinghaus adopted can be summarized in terms of three simple principles for the scientific study of mental processes that are not directly observable. These principles are as valid today as they were when Ebbinghaus first made use of them. First, it is necessary to find a way of converting the unobservable mental processes into observable behavior. Second, it is necessary to be able to measure this observable behavior reliably. Third, it is necessary to show that the behavior thus quantified varies systematically with other variables and experimental conditions.

The unobservable mental processes that Ebbinghaus wanted to study and measure were associations between ideas. Like almost all of his contemporaries, he assumed that memory reflects the existence of associations between ideas. He also thought that learning consists of the acquisition of associations, whereas forgetting reflects their loss. Ebbinghaus decided that the study of the acquisition and loss of associations would best be undertaken in a situation in which the associations to be learned were initially nonexistent. To that end he invented the nonsense syllable as a basic idea unit to be used in experiments on memory. A nonsense syllable is a meaningless single syllable consisting of two consonants separated by a vowel or a diphthong (e.g., WEZ, SIF). A single "lesson" to be learned and remembered consisted of a series of randomly chosen syllables. It was natural to imagine that no associations existed between and among the members of the series. The learning of a "lesson" (committing the series to memory) therefore would involve the formation and strengthening of associations between its constituent syllables. The process of learning could be captured by observing and measuring some behavior that could be assumed to be closely correlated with changes in the associations.

Methods and Results

In all his experiments Ebbinghaus was his sole subject. In numerous studies, in which he varied the conditions of learning and retention, he would learn and then test himself with a large number of different series of syllables. He would learn a given series by first reading and then repeating the sequence of syllables aloud to the beating of a metronome, at the rate of two and a half syllables per second, until he could produce the series faultlessly. The amount of effort required to master the series provided measures of both original learning and subsequent retention (or forgetting, the opposite of retention). Ebbinghaus adopted the number of readings, or the amount of time required for the learning of the series, as the measure of learning. Some time later he would relearn the same series, using the same method of reading and repeating the syllables. The comparison of initial learning and relearning scores provided a measure of what Ebbinghaus called savings. Ebbinghaus took savings to represent a measure of retention of the original learning.

Using these methods of measurement of memory, Ebbinghaus investigated a number of basic phenomena of learning and retention. The results of his experiments, concerning things such as the relation between the length of the series and the difficulty of learning it, the effects of the original overlearning of a series on its subsequent relearning, the advantages of distributed over massed practice, and the shape of the forgetting curve, turned out to be highly regular and lawful. Ebbinghaus exercised meticulous care in carrying out his experiments. Among other things, he went to great trouble in performing large numbers of replications of individual experiments. The resulting regularity and lawfulness of his findings greatly impressed other scientists.

In one particularly ingenious set of experiments Ebbinghaus measured and compared three kinds of associations: forward associations between adjacent members of a series, backward associations, and remote associations. In order to measure remote associations he would initially learn a series of syllables in a particular order, and subsequently relearn various series systematically derived from the original one. In these derived series the originally learned syllables were separated by a certain number of other syllables. For instance, if the original series is symbolized by A B C D E F … ("…" designating other syllables), then the derived series "skipping one syllable" would consist of A C E … B D F …, and the derived series "skipping two syllables" would consist of A D … B E … C F… Ebbinghaus found that the savings in learning these derived series varied systematically with the remoteness of the members of the derived series from one another in the originally learned series. These data suggested that in the course of learning a series of syllables, associations are formed not only between immediately adjacent syllables but also among remote ones, the strength of the remote associations between any two members of a series varying directly with the degree of their remoteness in the original series.

Influence

Ebbinghaus's work proved to be highly influential for a number of reasons. Despite the pioneering nature of his work, he did just about everything right by the standards of science. He replaced philosophical discussions about memory and its phenomena with tightly controlled experimental demonstrations of how memory could be measured and how memory performance could be found to be related to and determined by various independent variables. He discussed the sources of error and the problems of unreliability of measurement. He explained and demonstrated how one could measure fine gradations in mental processes that until then were thought to be scientifically intractable. He showed how the "higher" mental processes seemed to obey the same general kinds of laws that governed the "lower" processes. He explicitly and forcefully pointed out the intimate connection that exists between learning and memory, a realization that has guided the study of memory ever since. Like many other novel ideas introduced by Ebbinghaus, the connection between learning and memory is obvious in our day, but it had been overlooked by most thinkers before Ebbinghaus. Perhaps the most important innovation introduced by Ebbinghaus was his adoption of the basic study-and-test paradigm in which a subject learns some previously unknown material and is subsequently tested for retention of the studied material. The study-test paradigm contrasted sharply with the then current philosophical practice of discussing problems and phenomena of memory from the vantage point of existing associations.

Three features of Ebbinghaus's groundbreaking work that are most frequently mentioned in textbooks—his invention of the nonsense syllable; his serial learning task; and his adoption of the savings method as a measure of strength of associations—have had little direct influence on succeeding generations of memory researchers, who even shortly after 1885 rapidly adopted other methods and techniques of studying and measuring memory. Nonsense syllables turned out to vary greatly in meaningfulness and thus lost the advantage of their homogeneity. The serial learning task did not allow independent manipulation or assessment of stimulus and response functions in learning and retention. And the originally ingenious savings method was replaced with more direct methods of measuring retention and forgetting.

Ebbinghaus's most momentous single achievement consisted in his convincing demonstration that it is possible to reliably measure aspects of complex mental processes that are not directly observable. Almost as important were his general orientation and approach and his attitude and spirit in the matter of applying the methods of science to the study of the human mind. These were embraced by his contemporaries and have continued to inspire and guide the thinking of succeeding generations of students of psychology interested in learning and memory.

Ebbinghaus's pioneering role in the founding of the field of research on human learning and memory is universally acknowledged. Über das Gedächtnis represented a remarkable achievement of a great scientist, one that has left an indelible stamp on the study of one of the most fascinating problems of the human brain (or mind).

Bibliography

Ebbinghaus, Hermann (1885). Über das Gedächtnis: Untersuchungen zur experimentellen Psychologie. Leipzig: Duncker and Humblot. Trans. (1913) H. A. Ruger and C. E. Bussenius, Memory: A contribution to experimental psychology. New York: Teachers College, Columbia University. Reprint (1964), New York: Dover.

—— (1897). Grundzüge der Psychologie. Leipzig: Veit.

Hoffman, R. R., Bringmann, W., Bamberg, M., and Klein, R. (1987). Some historical observations on Ebbinghaus. In D. S. Gorfein and R. R. Hoffman, eds., Memory and learning: The Ebbinghaus centennial conference.

Hillsdale, NJ: Erlbaum. Postman, L. (1968). Hermann Ebbinghaus. American Psychologist 23, 149-157.

Roediger, H. L. (1985). Remembering Ebbinghaus. Contemporary Psychology 30, 519-523.

Slamecka, N. J. (1985). Ebbinghaus: Some associations. Journal of Experimental Psychology: Learning Memory, and Cognition 11, 414-435.

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