Divided Attention • 93This is the same procedure as in the previ-
ous experiment, but with the following modifi ca-
tions that make it more diffi cult: (1) The targets
in the memory set and the distractors are both let-
ters. In the previous experiment, the targets were
numbers and the distractors were letters. (2) Just
as in Schneider and Shiffrin’s previous experi-
ment (Figure 4.12), the targets and distractors
are changed on each trial. However, for this new
task, a target on one trial can be a distractor on
the next trial. For example, target stimulus P on
trial 1 becomes a distractor on trial 2. Also, the
target stimulus T on trial 2 was a distractor on
trial 1. This is called the varied mapping condition
because the rules keep changing from trial to trial.
● Figure 4.15 shows that performance was
worse in the varied mapping condition than in the
consistent mapping condition. Each data point is the
maximum performance achieved after many trials of
practice, when there was one target stimulus and four
stimuli in each test frame. The duration that each
frame was visible is plotted on the horizontal axis.
First look at the consistent mapping condition.
Performance reaches above 90 percent correct when the test
frame duration is only 80 ms. This speed is too fast for varied
mapping, so the presentation has to be slowed down by increas-
ing frame duration. When this is done, performance doesn’t
exceed 90 percent until each test frame is presented for 400 ms.
Clearly, the varied mapping condition is much more diffi cult.
Another important outcome of varied mapping is that par-
ticipants never achieved automatic processing. Schneider and
Shiffrin describe the processing used in the varied mapping
condition as controlled processing, because the participants
had to pay close attention at all times and had to search for
the target among the distractors in a much more focused and
controlled way than in the consistent mapping condition.
Let’s summarize the results of the experiments we have
discussed in this section. Divided attention is possible and can
become automatic if tasks are easy or well-practiced. Divided
attention becomes diffi cult and can require controlled pro-
cessing when the task is made too hard (also see Schneider &
Chein, 2003). For example, you may fi nd it easy to drive and
talk at the same time if traffi c is light on a familiar road. But as
traffi c increases, you see a fl ashing “Construction Ahead” sign,
and the road suddenly becomes rutted, you might have to stop
your conversation to devote all of your cognitive resources toTHE IMPORTANCE OF MEMORY IN OUR LIVES
and the recent phenomenon of people talking on cell phones● FIGURE 4.15 Comparing performance on the consistent
and varied mapping tasks. Note that the horizontal axis
indicates the duration of each test frame. These graphs show
that frames must be presented for longer durations to achieve
good performance in the varied mapping condition. (Source:
Based on data from R. M. Shiffrin & W. Schneider, “Controlled and Automatic
Human Information Processing: Perceptual Learning, Automatic Attending,
and a General Theory,” Psychological Review, 84, 127–190. Copyright © 1977
with permission of the American Psychological Association.)
60708010090Test frame duration (ms)0 100 200 300 400
Frame duration (ms)Consistent
Varied● FIGURE 4.14 Varied mapping condition for Schneider and Shiff rin’s
(1977) experiment. This is more diffi cult than the consistent mapping
condition because all the characters are letters and also because a
character that was a distractor on one trial (like the T) can become a target
on another trial, and a character that was a target on one trial (like the P)
can become a distractor on another trial. (Source: Reprinted from R. M. Shiffrin & W.
Schneider, “Controlled and Automatic Human Information Processing: Perceptual Learning,
Automatic Attending, and a General Theory,” Psychological Review, 84, 127–190. Copyright ©
1977 with permission of the American Psychological Association.)
Trial 1M TF LQ ER PA YC T......
PTrial 2G CM QH ZB VX PF A......
TA distractor
on trial 1In memory
set on trial 1(a)
(b)
(c)
(d)
DEMONSTRATION Detecting a Target
Cover ● Figure 4.14b, c, and d. Note the target stimulus in
(a). Then uncover (b) and determine if the target stimu-
lus is present in the sequence of frames in Figure 4.14b,
scanning from left to right. Now repeat this procedure
for the new target stimulus in (c) and the frames in (d).Copyright 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part.