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Forgetting is a nuisance, but it happens to all of us—why? There is a
phenomenon in human memory known as decay. Jenkins and Dallenbach believed the decay of
memory strength was a function of time. Their research concerned what happened during the time
span and how it could influence how much you forgot—or did not forget. They had their
participants memorize nonsense syllables and then tested their recall at 1, 2, 4, or 8 hours later.
According to Jenkins and Dallenbach, decay theory proposes that busy or not, if time between
memorization and recall is equivalent across participant groups, then the amount of forgetting will
be equivalent. WRONG! Participants who remained awake and working after memorizing the
syllables recalled less than those who were able to sleep and then were retested on awakening did.
This effect is a phenomenon called interference. The amount that you forget depends on how much
other “stuff’ you had to absorb and deal with in the interim and what you learned earlier is going to
compete with material learned later. This is called Interference Theory.
There are two types of interference:
Proactive interference (a.k.a. inhibition) deals with forward (pro) acting interference, the
detrimental impact that having learned List A has on your ability to remember a subsequently
learned List B. An experimental group tested on List B, the second list, after a retention interval,
did worse on recall of List B than did a control group who did not learn List A. (What else
might explain this? Serial position curves and the primacy effect).
Retroactive interference refers to the detrimental impact that learning List B has on previously
learned List A. This is backward-acting interference and occurs when something that you have
learned recently interferes with something that you learned in the past. For example, when an
experimental group learns List A, then List B, followed by a retention period and is asked to
recall List A ten minutes later, performance is poor. Learning List B interferes with memory for
List A.
Example of Proactive Interference/Inhibition Experiment Protocol
Experimental Learn List A Learn List B Retention Period Memory test
Group for List B
Control Group Learn List B Retention Period Memory test
for List B
The Control Group in this experiment usually performs better on the test of List B because they did
not have List A to interfere with what they learned later.
Example of Retroactive Interference/Inhibition Experiment Protocol
Experimental Learn List A Learn List B Retention Period Memory test
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Group for List A
Control Group Learn List B Retention Period Memory test
for List A
The Control Group in this experiment usually performs better on the test of List A because they did
not have List B to interfere with what they had learned previously.
Reasons for Memory Loss with Age
As people get older, their ability to remember tends to decrease. It takes longer for older people to
retrieve information, and sometimes they are unable to retrieve information that they are confident
is “in there somewhere.” Here are some of the factors that contribute to memory loss in older people.
. Proactive interference occurs when something we learned in the past interferes with something learned
more recently. This type of interference may be more of a problem for older people because they have
been exposed to more information than younger people have, and there is potentially more previously
learned material to interfere with what was learned later.
. State-dependent memory tells us that being in the same physiological state at the time of storage and
retrieval facilitates remembering. We change physiologically with age and physiological states
experienced at 65 may be much different from those experienced at younger ages.
. Environmental cues for memory also decrease as people grow older. Houses and other structures they
remember have been replaced, family and friends have died or moved away, streets and roads have
been replaced by expressways, and fields and forests have been replaced by buildings.
. Memory failures in older people may have a physiological cause. Neurons involved in a memory or in
the associations that would lead to a memory may have degenerated, or the supply of an important
neurotransmitter like acetylcholine may have decreased.
. Depression in the elderly may be a cause of memory loss. As a function of such factors as living alone,
being widowed, living far from one’s children, watching one’s friends and acquaintances become ill and
die, and their own deteriorating physical health are all more than adequate reasons for depression.
Depression brings limited attention. If the attention span of an elderly individual is impaired as a
concomitant of depression, memory impairment may follow.
BIOGRAPHICAL PROFILES
Hermann Ebbinghaus (1850—1909)
Born in Barmen, Germany, Ebbinghaus was instrumental in the development of the new
science of experimental psychology at the turn of the century. A professor at both Breslau and
Halle, he was the first experimentalist to conduct vigorous laboratory investigations of human
learning and memory. Using himself as a participant, Ebbinghaus memorized long lists of
nonsense syllables that he believed had no prior meaning or associative value. His research
resulted in several discoveries, including the finding that as the quantity of material to be
learned increases, the amount of time needed to learn it increases disproportionately, known as
Ebbinghaus’ Law, and the serial position curve.
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Endel Tulving (b. 1927)
Born in Estonia, Endel Tulving was educated at the University of Heidelberg and the
University of Toronto before obtaining his Ph.D. at Harvard in 1951. He taught at the
University of Toronto for most of his professional career. His major contributions include both
experimental and theoretical work on human memory. In particular, Tulving has introduced
many of the concepts that are today considered indispensable to understanding human
cognition and memory, including subjective organization, retrieval cues, and the distinction
between episodic and semantic memory.
Elizabeth F. Loftus (b. 1944)
Born in Los Angeles, Loftus earned her B.A. in psychology at UCLA in 1966 and her Ph.D. at
Stanford in 1970. She has been a professor of psychology at the University of Washington since
1975. Professor Loftus’ area of specialty is human memory. Her expertise is in the area of
eyewitness testimony, and she is often referred to as “the expert who puts memory on trial.”
Loftus has made a career of exploring the frailties and flaws of human memory, particularly
with respect to the validity of memories encoded under duress, such as when witnessing a
crime or being a victim of a crime. She is sought after as the expert witness who can explain to
juries the fallibility of human memory, and help them to understand that what the eyewitness
says he or she saw may, in reality, be due to post-event information that has been encoded and
incorporated into the original memory.
TIMELINE
Year Event
1859 Charles Darwin published On the Origin of the Species.
1885 Ebbinghaus published the first psychological study of memory.
19141918
World War I was fought.
1932 Frederic Bartlett published his findings on reconstructive memory, demonstrating
that memory is influenced by multiple subjective factors such as emotions and the
consistency of information.
19391945
World War II was fought.
1956 George Miller published “The Magic Number Seven Plus Or Minus Two: Some
Limits On Our Capacity For Processing Information,” outlining his work on short-
term memory.
1959 Donald Broadbent published Perception and Communication, outlining a new and
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important theory of attention.
1963 John F. Kennedy was assassinated.
1966 S. Sternberg published High Speed Scanning in Human Memory, providing the first
evidence that processing of searching information in short-term memory takes
place serially.
1968 Richard Atkinson and Richard Shiffrin introduced the “three-system” model of
memory.
1969 The first moon landing occurred.
1972 F. Craik and R. Lockhart published their levels of processing model of memory,
the most successful competitor to the three-system model.
1972 J. Bransford and J. Franks published the results of an experiment showing that
people use schemas in recalling information.
1974 The Vietnam War ended.
SUGGESTIONS FOR FURTHER READINGS
Berkerian, D. A. (1993). In Search of the Typical Eyewitness. American Psychologist, 48(5), 574–576.
Poses the question as to whether results of research in eyewitness testimony generalize to the
actual eyewitness.
Bruce, D. (1994). Lashley and the Problem of Serial Order. American Psychologist, 49(2), 93–103. An
overview of Lashley’s classic 1951 paper on serial order, with its foreshadowing of the coming
changes in linguistic and cognitive approaches to learning, memory, perception, and action.
Egeth, H. E. (1993). What Do We Not Know about Eyewitness Identification?