Short-Term Memory • 1292 shaded squares) to large (a 5 × 6 matrix with 15 shaded squares),
with half of the squares being shaded in each pattern. He found that
participants were able to complete patterns consisting of an average
of 9 shaded squares before making mistakes.
The fact that it is possible to remember the patterns in Della
Sala’s matrix illustrates visual coding. But how come the participants
could remember patterns consisting of as many as 9 squares? This
number is at the high end of Miller’s range of 5 to 9 and is far above
the lower estimate of 4 items from Luck and Vogel’s experiment
(Figure 5.8). Try answering this question. (For a possible answer, see
the footnote at the bottom of this page.*)Semantic Coding Semantic coding is representing items in terms
of their meaning. An example of semantic coding in STM is pro-
vided by an experiment by Delos Wickens and coworkers (1976).
● Figure 5.11 shows the experimental design for Wickens’ experi-
ment. On each trial, participants were presented with words related
to either (a) fruits (the “fruit group”) or (b) professions (the “profes-
sions group”). Participants in each group listened to three words (for
example, banana, peach, apple for the fruit group), counted back-
ward for 15 seconds, and then attempted to recall the three words.
They did this for a total of four trials, with different words presented
on each trial.
The basic idea behind this experiment was to create proactive inter-
ference, the decrease in memory that occurs due to prior learning (see
page 124), by presenting words in a series of trials from the same category. For example, for
the fruit group, banana, peach, and apple were presented on trial 1 and plum, apricot, and
lime were presented on trial 2.
Let’s consider the results for the fruit group, shown in ● Figure 5.12a. On the fi rst
trial the average percent recalled was 86 percent, but performance dropped on trials 2,
3, and 4 as additional names of fruits were presented. The blue data points indicate the
presence of proactive interference caused by repeated presentation of the names of fruits.
Evidence that this interference can be attributed to the meanings of the words (all
of the words were fruits) is provided by the results for the professions group, shown in
Figure 5.12b. As with the fruits group, performance is high on trial 1 and then drops
on trials 2 and 3 because all of the words are names of professions. But on trial 4, the
names of fruits are presented. Because these are from a different category, proactive
interference is reduced, which results in an increase in performance on trial 4. This
effect is called release from proactive interference.
What does release from proactive interference tell us about coding in STM? The
key to answering this question is to realize that the release from PI that occurs in the
Wickens experiment depends on the words’ categories (fruits, professions). Because plac-
ing words into categories involves the meanings of the words, the results of the Wickens
experiment demonstrate the operation of semantic coding in STM.- The beginning of the chapter makes the claim that “life is all memory.” How
has this claim been supported by considering what memory does for people
with the ability to remember and what happens when this ability is lost, as in
cases like that of Clive Wearing? - Describe Atkinson and Shiffrin’s modal model of memory, in terms of both
its structure (the boxes connected by arrows) and the control processes. Then
describe how each part of the model comes into play when you decide you
want to order pizza but can’t remember the pizzeria’s phone number.
TEST YOURSELF 5.1
● FIGURE 5.11 Stimuli for the Wickens et al. (1976)
experiment. Participants in the fruit group are
presented with the names of three fruits on each trial.
Participants in the professions group are presented
with the names of three professions on trials 1, 2,
and 3, and with the names of three fruits on trial 4.
Proactive interference based on meaning could occur
on trials indicated by the blue rectangles. (Source: Based on
D. D. Wickens, R. E. Dalezman, & F. T. Eggemeier, “Multiple Encoding of Word
Attributes in Memory,” Memory & Cognition, 4, 307–310, 1976.)Banana
Peach
ApplePlum
Apricot
LimeMelon
Lemon
GrapeOrange
Cherry
PineappleTrial 1(b) Professions(a) FruitsTrial 2 Trial 3 Trial 4Lawyer
Firefighter
TeacherDancer
Minister
ExecutiveGrocer
Doctor
EditorOrange
Cherry
PineappleTrial 1 Trial 2 Trial 3 Trial 4*With patterns such as the ones in Figure 5.10, it is possible to combine individual squares into subpatterns.
This is an example of chunking, which could increase the number of squares remembered, much as Chase and
Simon’s expert chess players remembered the patterns of chess pieces (page 127).Copyright 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part.