58 • CHAPTER 3 Perception
make about the environment. This theory was proposed to
account for our ability to create perceptions from stimulus
information that can be seen in more than one way. For
example, what do you see in the display in ● Figure 3.14a?
Most people perceive a blue rectangle in front of a red
rectangle, as shown in Figure 3.14b. But as Figure 3.14c
indicates, this display could have been caused by a six-sided
red shape positioned either in front of or behind the blue
rectangle.
The theory of unconscious inference includes the likeli-
hood principle, which states that we perceive the object that
is most likely to have caused the pattern of stimuli we have
received. Thus, we infer that it is likely that Figure 3.14a is a
rectangle covering another rectangle because of experiences
we have had with similar situations in the past. Helmholtz
therefore described the process of perception as being simi-
lar to the process involved in solving a problem. For per-
ception, the problem is to determine which object has caused a particular pattern of
stimulation, and this problem is solved by a process in which the observer applies his or
her knowledge of the environment in order to infer what the object might be. In cases
such as the overlapping shapes in Figure 3.14, this process is unconscious, hence the
term unconscious inference. (See Rock, 1983, for a modern version of this idea.)
We can apply this idea that perception involves a process similar to solving a prob-
lem to Crystal’s attempts to identify the faraway shape on the beach. Based on what
she saw at fi rst, she hypothesized “driftwood” based on the image on her receptors and
her knowledge of which objects are often found on the beach. But as she got closer, she
decided it was more likely that the image was caused by the umbrella she had seen the
day before. Although in this example Crystal used a conscious reasoning process that
was much slower than Helmholtz’s unconscious inference, the basic principle is similar
to his proposal that perception involves an inferential process that resembles the pro-
cess involved in solving a problem.THE GESTALT LAWS OF ORGANIZATION
About 30 years after Helmholtz proposed his theory of unconscious inference, a group
called the Gestalt psychologists proposed another approach. The goal of this approach
was the same as Helmholtz’s—to explain how we perceive objects—but the empha-
sis was different. The Gestalt psychologists were concerned with perceptual organiza-
tion, the way elements are grouped together to create larger objects. For example, in
● Figure 3.15, some of the black areas become grouped to form a Dalmatian and others
are seen as shadows in the background. The Gestalt psychologists proposed a number
of laws of perceptual organization that indicate how elements in the environment are
organized, or grouped together.
The starting points for the Gestalt laws are things that usually occur in the environ-
ment. Consider, for example, the rope in ● Figure 3.16a that Crystal saw as she was
running down the beach (Figure 3.1c). Remember that when she grabbed one end of the
rope and fl ipped it, it didn’t surprise her that it was one continuous strand (page 48).
The reason this didn’t surprise her is that even though there were many places where
one part of the rope overlapped another part, she didn’t perceive the rope as consisting
of a number of separate pieces, but perceived the rope as continuous. She perceived
it this way because when one object overlaps another in the environment, the over-
lapped (underneath) object usually continues unbroken beneath the object on top. This
is illustrated by the highlighted segment of the rope in Figure 3.16b.
Observations such as this led the Gestalt psychologists to propose the law of good
continuation, which states: Points that, when connected, result in straight or smoothly
curving lines are seen as belonging together, and the lines tend to be seen in such a way● (^) FIGURE 3.14 The display in (a) is usually interpreted as being
(b) a blue rectangle in front of a red rectangle. It could, however,
be (c) a blue rectangle and an appropriately positioned six-sided
red fi gure.
(a)(b) (c)
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