Page 176 - Foundations of Cognitive Psychology : Core Readings

180 Philip G. Zimbardo and Richard J. Gerrig

Figure 7.38
Role of parts in object recognition. The deletions of visual information in the middle column leave
the parts intact. In the right-hand column, the deletions disrupt the parts. Do you agree that the
objects are easier to recognize in the middle versions?

Recovery of components alone, however, will not always be sufficient to rec-
ognize an object (Tarr, 1994). One difficulty, as shown in figure 7.39, is that you
often see objects from radically different perspectives. The appearance of the
parts that make up the object may be quite different from each of these per-
spectives. As a hedge against this difficulty, you must store separate memory
representations for each of the major perspectives from which you view stan-
dard objects (Tarr & Pinker, 1989). When you encounter an object in the envi-
ronment, you may have to mentally transform the percept to determine if it
correctly matches one of those views. Thus to recognize a gray, oddly shaped,
medium-size, furry thing as a cat, you must recognize it both as an appropriate
combination of geons and as that appropriate combination of geons from a
specific viewpoint.

The Influence of Contexts and Expectations
What also might help you recognize the cat, however, is to find that gray,
oddly shaped, medium-size, furry thing in its accustomed place in your
home. This is the top-down aspect of perception: expectations can influence
your hypotheses about what is out there in the world. Have you ever had
the experience of seeing people you knew in places where you didn’t expect