66 • CHAPTER 3 Perception
This effect of semantic knowledge on our ability to perceive was illustrated in an
experiment by Stephen Palmer (1975), using stimuli like the picture in ● Figure 3.28. Palmer
fi rst presented a context scene such as the one on the left and then briefl y fl ashed one of
the target pictures on the right. When Palmer asked observers to identify the object in the
target picture, they correctly identifi ed an object like the loaf of bread (which is appropri-
ate to the kitchen scene) 80 percent of the time, but correctly identifi ed the mailbox or the
drum (two objects that don’t fi t into the scene) only 40 percent of the time. Apparently
Palmer’s observers were using their knowledge about kitchens to help them perceive the
briefl y fl ashed loaf of bread. The effect of semantic regularities is also illustrated by the
“multiple personalities of a blob” illustration in Figure 3.6, because our perception of
the blob depends on our knowledge of what is usually found in different types of scenes.- What is speech segmentation? How does the author’s description of his
Telemundo experience illustrate how perception is infl uenced by knowledge? - Describe Helmholtz’s theory of unconscious inference. What does it say about
the role of knowledge in determining perception? - Describe the Gestalt laws of perceptual organization. Why do we say that these
laws are based on what usually occurs in the environment? What is the relation
between these laws and Helmholtz’s likelihood principle? Why can the Gestalt
laws be called “heuristics”? - What are regularities in the environment? Describe physical regularities and
semantic regularities. Be sure you understand the following concepts and
experiments: oblique effect; light-from-above heuristic; Hollingworth gym
experiment; Palmer kitchen experiment; multiple personalities of a blob.
Neurons and Knowledge About the Environment
Our discussion of how perception is linked to the perceiver’s knowledge of the envi-
ronment has so far focused on behavioral examples. But there is neural activity behind
every behavior, and research has demonstrated connections between neural activity,TEST YOURSELF 3.2
● FIGURE 3.28 Stimuli used in Palmer’s (1975) experiment. The scene at the left is
presented fi rst, and the observer is then asked to identify one of the objects on the right.
(Source: S. E. Palmer, “The Eff ects of Contextual Scenes on the Identifi cation of Objects,” Memory and
Cognition, 3, 519–526, 1975. Reprinted by permission of the Psychonomic Society, Inc.)Context scene Target objectCBACopyright 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part.