104 • CHAPTER 4 Attention
shown that location-based and object-based attention activate different areas of the
brain. This result supports the idea that location-based attention and object-based
attention involve different mechanisms (Shomstein & Behrmann, 2006).Feature Integration Theory
So far we have described a number of ways that attention contributes to our aware-
ness. When we selectively attend, we focus our awareness on one thing among
many; when we divide our attention, we spread our awareness or carry out multiple
tasks; when we scan a scene, we direct awareness to different parts of a display or
scene.
Now we are going to consider another function of attention, which is notable
because we are unaware of its operation. This property of attention, which operates in
the background outside of our awareness, enables
us to perceive an object’s visual features as belong-
ing together. To appreciate why it is necessary to
propose a mechanism that enables us to perceive
an object’s features as belonging together, think
back to Chapter 2 (page 37), where we intro-
duced a person observing a rolling red ball, shown
again in ● Figure 4.31. Remember that the ball’s
features—color (red), shape (round), movement
(to the right) —are processed in different parts of
the person’s brain, so the ball’s features are sepa-
rated physiologically. The point of this example
was that even though observing the ball activates
separate areas in the brain, we perceive one object,
a red ball, moving to the right.
Anne Treisman (1986, 1998) proposed a the-
ory, called feature integration theory, to explain
how we perceive these initially separated features
as part of the same object. In her theory, the fi rst
step in processing an image of an object is the
preattentive stage (the fi rst box in the fl ow dia-
gram in ● Figure 4.32). In the preattentive stage,
objects are analyzed into separate features. For
example, the rolling red ball would be analyzed
into the features color (red), shape (round), and
movement (to the right). Because each of these
features is processed in a separate area of the
brain, they exist independently of one another at
this stage of processing.
The idea that an object is automatically
broken into features may seem counterintuitive
because when we look at an object, we see the
whole object, not an object that has been divided
into its individual features. The reason we aren’t
aware of this process of feature analysis is that it
occurs early in the perceptual process, before we
have become conscious of the object. Thus, when
you see this book, you are conscious of its rectan-
gular shape, but you are not aware that before you
saw this rectangular shape, your perceptual system● FIGURE 4.32 Steps in Treisman’s feature integration theory. Objects
are analyzed into their features in the preattentive stage, and then the
features are combined later with the aid of attention.Preattentive
stageObject PerceptionAnalyze into
featuresCombine
featuresFocused
attention
stage● FIGURE 4.31 As this person watches the red ball roll by, diff erent areas
of his cortex are activated by diff erent properties of the ball. These areas
are in separated locations in the cortex, although there is communication
between them. (Source: From E. B. Goldstein, Sensation and Perception, 8th ed., Fig. 6.18.
Copyright © 2010 Wadsworth, a part of Cengage Learning. Reproduced with permission.
http://www.cengage.com/permissions.)Depth
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