FOCUS ON RESEARCH Attention and the Brain

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Chapter 3 Sensation and Perception
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FIGURE
3.31
The Stroop Task
Look at this list of words and,
as rapidly as possible, call out
the color of the ink in which
each word is printed. How did you do?
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Tutorial: The Stroop Task
Dividing Attention
Often you can divide your attention efficiently enough to allow you to perform more
than one activity at a time (Damos, 1992). You can drive a car, listen to the radio, sing
along, and keep a beat by drumming on the steering wheel. However, your attention
cannot be divided beyond a certain point without a loss in performance and mentalprocessing ability. The reason is that attention is a limited resource. If you try to spread
it over too many targets, you “run out” of attention.
Still, it can sometimes be hard to keep your attention focused rather than divided.
Look at the list of words in Figure 3.31 and, as rapidly as possible, call out the color of
the ink in which each word is printed. This Stroop task (Stroop, 1935) is not easy,
because your brain automatically processes the meanings of the familiar words in the
list. These meanings then compete for attention with the responses you are supposed
to give. To do well, you must focus on the ink color and not allow your attention to
be divided between color and meaning. Children just learning to read have far less trouble with this task, because they don’t yet process the meanings of words as automatically as experienced readers do.
Although you can walk while talking, or drive while listening to music, you would
find it virtually impossible to read and talk at the same time. Why is it sometimes so
easy and at other times so difficult to do two things at once? When one task is so automatic as to require little or no attention, it is usually easy to do something else at the
same time (Schneider, 1985). Even when two tasks require attention, it may still be possible to perform them simultaneously if each taps into different kinds of attention
(Wickens, 2002; Wickens et al., 1992). Some types of attention are devoted to perceiving incoming stimuli. Others handle making responses. This specialization of attention
allows a skilled pianist to read musical notes and press keys simultaneously the first
time through a piece. Apparently, the human brain can manage more than one type of
attention and more than one spotlight of attention (Wickens, 1989). This notion of different types of attention also helps explain why an experienced driver can listen to the
radio while steering safely. If two tasks require the same kind of attention, however,
performance on both tasks will suffer (Just et al., 2001).
W
hat happens in the brain as people
try to attend to more than one
source of information at the same
FOCUS ON RESEARCH
Attention and the Brain
time?
■ What was the researchers’ question?
If directing attention to more than one task causes extra mental work to be done, there
should be evidence of that work in brain activity. One possibility is that informationprocessing activity in the brain should slow down. Does it? This was the question asked
by one research team.
■ How did the researchers answer the question?
Allan J. Nash and Mercedes Fernandez (1996) examined the brain processing speed of
participants engaged in various tasks. Sixteen college students heard high and low tones
and saw red and green light flashes. They were asked to respond as quickly as possible
to the identified target stimulus. On some trials they were to ignore tones and respond
only to one of the lights, and on other trials they were to respond to one light and keep
a running count of one of the tones. In short, the participants either attended to one
task (responding to a light) or split their attention between two tasks (responding to a
light and counting tones). The speed of the participants’ reactions to the flashing light
was measured throughout the experiment.