Developmental psychology.pdf

Memory 247
Figure 9.12
Interference of Prior Experience.
These results show that the larger
the number of previously learned
lists, the lower the accuracy of recall.
Each point represents the findings of
a single study (Underwood, 1957a).
5 10 15 .
Number of previous lists
20
In an impressive demonstration of proactive inhibition, a psychologist compared
several studies of memory by more than a dozen different investigators. These
studies had diverse aims, but in each instance it was known how much verbal material
the subjects had recalled 24 hours after the original learning and how many similar
lists had been learned before the critical list. It was found that the accuracy of recall
on the critical list was directly related to the number of lists learned previously. The
more items learned earlier, the poorer was the recall on the later list (Figure 9.12).
Retroactive Inhibition Another type of interference follows the opposite model. In
retroactive inhibition, later memories interfere with the recall of something learned
earlier. The experimental and control subjects both memorize task A and then the
experimental group learns task В while the control group performs an unrelated activity.
According to retroactive inhibition, the group that learned task В will show a poorer
memory for task A (Figure 9.13).
Group
Experimental
Control
First Second
Learning Learning
Session Session Recall
Task A Tasks Task A
Task A
Task Л
Figure 9.13
Retroactive Inhibition. The control
group rests or does an unrelated task
during the second learning session.
In one instance, two college students memorized lists of nonsense syllables and
then engaged in various activities or went to sleep. Retention was tested one, two, four,
and eight hours later, and it was found that memory was better after any amount of
sleep than after a comparable amount of time spent in activity while awake (Jenkins
& Dallenbach, 1924; Figure 9.14).
Cockroaches were used in another study of retroactive inhibition. At the outset
every cockroach was trained to avoid its natural response of running into a shaded
area at the end of a training box. If it did, the cockroach received an electric shock
through the floor. Afterward, the experimental subjects were rendered inactive by inducing
them to crawl between layers of tissue paper, where they remained motionless,
in so-called "animal hypnosis," until removed and tested for retention. Control subjects