occurrence of other events. When memory for an event is undermined by
events that precede it, the result is calledproactive interference.Whenmemory
for an event is undermined by events that follow it, the result is calledretroac-
tive interference.
A variety of experimental paradigms have been used to demonstrate inter-
ference (see Klatzky, 1980, or Watkins, 1979, for a review). The classic demon-
stration of retroactive interference comes from Jenkins and Dallenbach (1924).
In their experiment, subjects were first presented a list of nonsense syllables,
then spent the following 8 hours either asleep or awake, and then tried to recall
the nonsense syllables. The subjects who remained awake, and so experienced
more interfering events, recalled fewer syllables than did the subjects who went
to sleep. This experiment is not the ideal demonstration of retroactive interfer-
ence, though, because the subjects who experienced less interference also expe-
rienced a night of sleep. Maybe people are more motivated or less fatigued
after sleeping, and so perform better on memory tests.
An example of a better controlled experiment demonstrating interference is
provided by Kalbaugh and Walls (1973; also see Barnes & Underwood, 1959;
McGeoch, 1942; Melton & Irwin, 1940). They required their eighth-grade sub-
jects to study a critical passage describing the essential biographical details of a
fictional character. Some subjects read no other passages while other subjects
read either two or four other biographical passages. The additional passages
were presented either before the critical passage or after the critical passage. As
summarized in figure 14.5, the experiment demonstrated both retroactive and
Figure 14.5
Proactive and retroactive interference. Based on Kalbaugh and Walls, 1973.
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