2nd Edition

Chapter 9

Interactive exercise



Accessibility/availability distinction:
Accessibility refers to the ease with which a stored memory can be retrieved at a given point in time. Availability refers to the binary distinction indicating whether a trace is or is not stored in memory.
Associative blocking:
A theoretical process hypothesized to explain interference effects during retrieval, according to which a cue fails to elicit a target trace because it repeatedly elicits a stronger competitor, leading people to abandon efforts to retrieve the target.
Collaborative inhibition:
A phenomenon in which a group of individuals remembers significantly less material collectively than does the combined performance of each group member individually when recalling alone.
Competition assumption:
The theoretical proposition that the memories associated to a shared retrieval cue automatically impede one another’s retrieval when the cue is presented.
Contextual fluctuation:
The gradual and persistent drift in incidental context over time, such that distant memories deviate from the current context more so than newer memories, thereby diminishing the former’s potency as a retrieval cue for older memories.
Cue-overload principle:
The observed tendency for recall success to decrease as the number of to-be-remembered items associated to a cue increases.
Forgetting curve/retention function:
The logarithmic decline in memory retention as a function of time elapsed, first described by Ebbinghaus.
Incidental forgetting:
Memory failures occurring without the intention to forget.
Infantile amnesia:
Tendency for people to have few autobiographical memories from below the age of five.
The phenomenon in which the retrieval of a memory can be disrupted by the presence of related traces in memory.
Motivated forgetting:
A broad term encompassing intentional forgetting as well as forgetting triggered by motivations, but lacking conscious intention.
Part-set cuing impairment:
When presenting part of a set of items (e.g. a category, a mental list of movies you want to rent) hinders your ability to recall the remaining items in the set.
Proactive interference:
The tendency for earlier memories to disrupt the retrievability of more recent memories.
Retrieval-induced forgetting (RIF):
The tendency for the retrieval of some target items from long-term memory to impair the later ability to recall other items related to those targets.
Retrieval practice paradigm:
A procedure used to study retrieval-induced forgetting.
Retroactive interference:
The tendency for more recently acquired information to impede retrieval of similar older memories.
Trace decay:
The gradual weakening of memories resulting from the mere passage of time.
The proposition that the associative bond linking a stimulus to a memory trace will be weakened when the trace is retrieved in error when a different trace is sought.


Research activities: factors affecting retrieval

Activity 1

Research has demonstrated that contextual fluctuations that occur between encoding and retrieval of information significantly alter individuals’ ability to retrieve memories. Think about times when you have encountered this problem and what realistic revision strategies you could use to minimize these effects.

Activity 2

Consider the possible implications of collaborative inhibition for the successful outcomes of group assignments, political decisions, and brainstorming. How could you reduce the impact of this phenomenon on your productivity and still be involved in group processes?


A video clip about Jill Price: The woman that never forgets.
Another interview with Jill Price.
Another interview with Jill Price.
A CBS news report about superior autobiographical memory.

Please find below biographies of three important researchers in the field of memory: Hermann Ebbinghaus, Leo Joseph Postman, John A. McGeoch, and Arthur Weever Melton.

Hermann Ebbinghaus

Personal history

Hermann Ebbinghaus was born on January 24, 1850 in Barmen, Germany to a merchant family. His early studies included history and philology, though he settled on philosophy while at the University of Bonn. His studies there were interrupted by his service in the Prussian army during the Franco–Prussian War. Returning to the University of Bonn to receive his Ph.D. in 1873 upon completion of his dissertation, On Hartmann’s Philosophy of the Unconscious, Ebbinghaus moved to Berlin. \

After a few years, he ventured to France and then England, where he briefly taught at a couple of small English schools and discovered Gustav Fechner’s Elements of Psychophysics. Reading the used copy of Fechner’s book helped inspire Ebbinghaus’s interest in the quantitative study of memory, as he had already developed a desire to better understand the process of forgetting.

In 1885, after Ebbinghaus was hired as a professor at the University of Berlin and subsequently founded a new journal called (in English) The Psychology and Physiology of the Sense of Organs. Although Ebbinghaus was considered an inspiring teacher by many and founded two psychological laboratories while in Germany, his sparse publication record stymied his career in Berlin, prompting his move to the University of Breslau, where he became a full professor in 1894. In 1905, Ebbinghaus made what would become his last move, this time to the University of Halle. It was there, 59 years after his birth on February 26, that Ebbinghaus succumbed to pneumonia. Poetry left a substantial mark on Ebbinghaus’s life, having enjoyed it so thoroughly that some of his experimental techniques involved memorizing passages of famous works.


Although Ebbinghaus would occasionally employ meaningful stimuli, such as poetry, in his memory experiments, he preferred a technique he developed that would become the standard for numerous researchers to follow. In order to avoid the potential confound created by the use of meaningful words with pre-existing semantic associations, he created over 2000 consonant–vowel–consonant combinations, forming nonsense syllables.

Ebbinghaus famously used himself as his sole subject for his tedious studies, drawing a random selection of the syllables, repeating them at a constant rate (thanks to a metronome) and later recalling them, repeating the process until he was able to get the list correct twice in a row.

Other measures of retention included recall (either free recall or serial recall), item recognition, and savings—the reduction in the amount of time necessary to relearn material to criterion after having studied it previously, indicating that memories often remain available even if they’re not consciously accessible at the time. Consciousness also was a factor in Ebbinghaus’s distinction between involuntary retrieval, when memories pop into mind spontaneously, and voluntary memory, which requires a willful attempt to bring a specific memory to mind. His sentence completion test not only became a standard implicit measure of memory, it became incorporated into the Binet–Simon intelligence scale.

Ebbinghaus’s experiments, which carefully controlled for factors like the time of day and even food intake, produced the learning and forgetting curves that would forever be attributed to the German researcher. As described in his 1885 monograph, Über das Gedächtnis (“On Memory”), memory increases with additional study repetitions, with the greatest amount of learning occurring on the early repetitions. Plotting memory as a function of the delay between learning and recall revealed an exponential forgetting curve, with the steepest declines occurring early on but eventually flattening out. Overtraining items (i.e., continuing to study pairs beyond the point of recallability), reduces the likelihood of forgetting and produces a shallower forgetting curve.

Ebbinghaus analyzed his recall data in a novel way, indicating the probability of recall based on when in a study list the item is presented. The resulting U-shaped serial position curve revealed primacy and recency effects (i.e., higher recall probabilities for items early and late in the list, respectively).

The rigorous methodology and analysis techniques advanced by Ebbinghaus, though criticized as literally meaningless by some, inspired enormous growth in memory research across the globe, especially in the United States. While he was not the first to study psychology empirically, he standardized the reporting of results, dividing his publication into an introductory section, followed by sections on the results, methods, and discussion. Generations of German students were influenced by his textbook on general psychology, translated as The Foundations of Psychology, and the follow-up that was published after his death. The Ebbinghaus Illusion, an optical illusion of relative size perception, also lives on in contemporary cognitive psychology research.


Ebbinghaus, H. (1885). Über das gedächtnis: Untersuchungen zur experimentellen psychologie. Leipzig: Duncker & Humblot.

Ebbinghaus, H. (1902). Grundzüge der psychologie. 1. Band, 2. Theil. Leipzig: Veit & Co.

Ebbinghaus, H. (1913). Grundzüge der psychologie. 1.-3. Auflage, fortgeführt von E. Dürr. Leipzig: Veit & Co.

Leo Joseph Postman

Personal history

Leo Postman was born on June 7, 1918 in St. Petersburg, Russia. He would soon move to New York City and eventually enroll in the College of the City of New York, where he earned his Bachelor of Science degree in 1943. From there, he enrolled in Harvard University’s doctoral program. During his time in graduate school, he was a teaching assistant, helping to grade undergraduates’ psychology papers, including that of his future wife. He earned his Ph.D. in 1946 and taught until 1950, save for a year at Indiana University. In that year, he moved to the University of California, Berkeley, where both he and his wife, Dorothy Lerman Postman, would work for many years. Quickly after arriving, he was named chair of the department of psychology.

He founded the Institute of Human Learning at Berkeley in 1961, later renamed the Institute for Cognitive and Brain Sciences. He headed the Institute until 1977 and retired from teaching in 1987. In between, Postman founded the Journal of Verbal Learning and Verbal Behavior, editing it from 1962 to 1968, when he was elected president of the Western Psychological Association. In 1974 he won the Warren Medal of the Society of Experimental Psychologists. In 2002, the Review of General Psychology listed Postman as a member of the 100 most eminent psychologists of the century. Postman’s wife died following a long illness a year before Postman himself was to pass away of heart failure in Marblehead, Massachusetts on April 22, 2004 at the age of 85.


After World War II, Postman helped lead psychology’s transition from the more theoretical to the experimental, producing, with the help of James Egan, one of the fundamental textbooks of the new field called Experimental Psychology: An Introduction. In 1947 his book, co-authored with Gordon Allport, called The Psychology of Rumor, systematically investigated how rumors are created and spread, a hot topic during the stressful period following the War. At Berkeley, Postman’s work largely focused on perception and its interaction with motivation and emotion, though he would shift his emphasis to incidental learning and forgetting.

Postman has been credited as constructing modern interference theory, which posits that forgetting is mainly a result of a combination of retroactive and proactive interference, as well as various aspects of the current mnemonic landscape. Postman’s view of forgetting—specifically his response-set suppression hypothesis—made an early reference to a possible inhibitory mechanism, in which an executive control selector mechanism was thought to simultaneously strengthen currently relevant information while suppressing outdated material.In many ways, this theory could be seen as related to the mechanisms thought to underlie retrieval-induced forgetting.

Though he will be remembered for his forgetting research and closing out the classical interference era, he spent the last years of his life investigating methods to minimize interference and preserve memories.


Allport, G. W., & Postman, L. (1947). The psychology of rumor. New York: Holt.

Postman, L. (1962). Psychology in the making: Histories of selected research problems. New York: Alfred A. Knopf.

Postman, L. (1961). The present status of interference theory. In C. N. Cofer (Ed.), Verbal learning and verbal behavior (pp. 152–179). New York, NY: McGraw-Hill.

Postman, L., Bruner, J. S., & McGinnies, E. (1948). Personal values as selective factors in perception. Journal of Abnormal and Social Psychology, 43, 142–154.

Postman, L., Stark, K., & Fraser, J. (1968). Temporal changes in interference. Journal of Verbal Learning and Verbal Behavior, 7, 672–694.

Postman, L., & Underwood, B. J. (1973). Critical issues in interference theory. Memory & Cognition, 1, 19–40.

John A. McGeoch

Personal history

Born on October 9, 1897, John A. McGeoch was trained as a functionalist under Harvey A. Carr. He received his Ph.D. from the University of Chicago in 1926 after having defended his dissertation called A study in the Psychology of Testimony. He accepted a position at Washington University in St. Louis. There he encountered and mentored Arthur Melton before moving to the University of Arkansas in 1928. He would make three other academic moves in his life: to the University of Missouri, where he was chairman of the Psychology Department; then to Wesleyan University; and finally the University of Iowa, where he held the equivalent position. Tragically, McGeoch died of a stroke just before his 45th birthday in 1942.

McGeoch’s seminal work, The Psychology of Human Learning: An Introduction, was published posthumously that same year. Originally, McGeoch had planned to publish the work contained in this textbook as part of a two-volume compendium of human learning research. However, McGeoch’s ill health and multiple moves eventually forced him to attempt to rewrite his draft as a briefer summary, intended as a textbook.


McGeoch has been heavily criticized for focusing on contrived, basic research with little to no practical outlets. However, this reputation stands in contrast to much of his earlier research. For instance, McGeoch’s dissertation was based on fieldwork he carried out with children in their East St. Louis classrooms. He was interested in the relationship between memory accuracy for staged eyewitness events, for instance, and intelligence (based on either background or the Army Alpha test—a short answer test designed to measure the general intelligence of new recruits). Additionally, McGeoch tested memory for real-world stimuli such as poetry, attempted to measure emotions, and better understand how juvenile delinquency affects suggestibility.

It was only later in his career that McGeoch took to carefully controlled experimental studies conducted within the confines of the laboratory. McGeoch’s laboratory studies, which propelled him to fame in the verbal learning arena, also tapped memory phenomena that have profound influences on our everyday lives.

McGeoch broke away from the then common assumption that most forgetting occurs simply as a function of passing time, as memories passively decay. Instead, McGeoch argued in his 1932 paper, Forgetting and the Law of Disuse, that interference created by the addition of new memories actually causes the difficulties in recalling older information. For McGeoch, this retroactive inhibition results from response competition between old and new memories arising during recall. He then methodically set out to characterize retroactive interference, trying to let the data speak for itself, rather than reaching to create a grand theory.


McGeoch, J. A. (1928b). Intelligence and the ability to report. American Journal of Psychology, 40, 596–599.

McGeoch, J. A. (1928c). The relation between different measures of the ability to report. American Journal of Psychology, 40, 592–596.

McGeoch, J. A. (1932). Forgetting and the law of disuse. Psychological Review, 39, 352–370.

McGeoch, J. A. (1942). The psychology of human learning. New York: Longmans, Green.

Arthur Weever Melton

Personal history

Born on August 13, 1906 in Fayetteville, Arkansas, Arthur Melton began his career in psychology as an undergraduate at Washington University at the age of 18. A year after graduating, in 1928, Melton’s first paper, with his undergraduate mentor, John A. McGeoch, called The Comparative Retention Value of Maze Habits and of Nonsense Syllables was published in the Journal of Experimental Psychology. In it, Melton laid out his functional approach to the study of human behavior. McGeoch’s early theory of forgetting laid the seed for Melton’s contribution to interference theory, but that was to come following his Ph.D. studies at Yale University, beginning in 1928 under the supervision of Edward S. Robinson, another functionalist interested in verbal learning.

While in graduate school, Melton worked on a project investigating how museumgoers behaved and which methods of instructing children in science museums were most effective. After receiving his Ph.D. in 1932, he continued to teach at Yale until 1935 before becoming the Chair of Psychology at the University of Missouri, a position held up to that time by McGeoch. In the wake of World War II, Melton joined the faculty at Ohio State University, where he stayed for 3 years until he was appointed director of the Air Force’s Human Resources Research Center in 1951 (he was a brigadier general in the Air Force Reserve). Following his 12-year tenure at the Research Center, he moved to the University of Michigan, remaining there until his retirement in 1974.

Beyond Melton’s numerous empirical findings and informative theories, he left a legacy as a strong advocate for rigorous experimental designs that avoided the many pitfalls facing researchers, such as confounds, while attempting to more fully understand effects by testing multiple levels of factors whenever possible. As editor of the Journal of Experimental Psychology for 12 years and as chief editorial advisor to the American Psychological Association, he used every opportunity to encourage researchers to subscribe to these goals. Melton was recognized by the American Psychological Association with a Gold Medal Award for his lifetime achievements in the experimental study of human learning in 1976. Previously, he had also been elected to the National Academy of Sciences in 1969. Melton died on November 5, 1978.


While conducting his museum studies at Yale, Melton used dwell time (i.e., the length of time that visitors spend in front of museum displays) as his dependent measure, looking at how it varied as a function of season, among other factors. He concluded that museums attract different types of people with different goals and competing interests. These studies typified Melton’s drive to use systematic naturalistic observations to better understand the functional relationships underlying the generalizations culled from the data.

In his later work, McGeoch importantly added a second component to the model of forgetting advanced by McGeoch. To explain forgetting (and retroactive interference, specifically), McGeoch emphasized response competition between old and newly learned associations when people are recalling information. Melton and his collaborator, Irwin, proposed a second factor, X—a form of unlearning, which also contributed to retroactive interference by weakening the older associative bonds during the learning of new information. The resulting two-factor theory of interference, explicated in a 1940 paper, helped shape the research in the classical interference era and continues to impact on research to this day. At Michigan, Melton employed the Brown–Peterson paradigm to study short-term memory.

In Melton’s landmark 1963 paper, Implications of Short-Term Memory for a General Theory of Memory, he made the case that short-term memory, rather than being an entirely distinct entity from long-term memory, could be incorporated into a general theory of memory. The free recall effect commonly called the Melton Lag Effect describes his finding that the recall probability is related to the number of items separating the two items in the study list. Thus, it is more likely that, after recalling a particular item, people will next recall an item that had appeared near the recalled item during learning.


Melton, A. W., & Irwin, J. M. (1940). The influence of degree of interpolated learning on retroactive inhibition and the overt transfer of specific responses. American Journal of Psychology,53,173–203.

Melton, A. W., & McGeoch, J. A. (1929). The comparative retention values of maze habits and nonsense syllables. Journal of Experimental Psychology,12, 392–414.

Melton, A. W. (1963). Implications of short-term memory for a general theory of memory. Journal of Verbal Learning and Verbal Behavior, 2, 1–21.

Melton, A. W. (1936). The methodology of experimental studies of human learning and retention. I. The functions of a methodology and the available criteria for evaluating different experimental methods. Psychological Bulletin,33, 305–94.

Melton, A. W. (1967). Repetition and retrieval from memory. Science,158, 232.