MIT Encyclopedia of the Cognitive Sciences - Cryptome

ility that an object is recognized by comparing it to
multiple, viewpoint-dependent representations in long-term
memory, rather than to a single, viewpoint-independent representation.
Relatively little is known about the physiological mechanisms
underlying shape perception, but researchers have
located neurons in the inferotemporal cortex (IT) that
respond better to some shapes than to others, even when
these shapes are not identified with specific previously
learned objects. Whereas the primary VISUAL CORTEX initially
codes basic features such as orientation, size, and
color, area IT codes much more complex features such as
particular shapes, or combinations of shapes and colors
(Tanaka 1993). Neurons in area IT also have similar shape
selectivity regardless of the cue that defines the shape (e.g.,
luminance-, texture-, or motion-defined shapes; Sary et al.
1995), the size and position of the shape (Ito et al. 1995;
Logothetis, Pauls, and Poggio 1995), or the presence or
absence of partially occluding contours (Kovacs, Vogels,
and Orban 1995). These recent discoveries suggest that area
IT plays a significant role in shape constancy and recognition,
but other cortical areas may be involved in the use of
shape to guide the manipulation of objects (Goodale and
Milner 1992; see also VISUAL PROCESSING STREAMS). Additional
physiological and psychophysical research in the next
few years undoubtedly will increase our understanding of
the physiological processes underlying shape perception.
See also ILLUSIONS; PICTORIAL ART AND VISION; SPA-
TIAL PERCEPTION; TOP-DOWN PROCESSING IN VISION
—Allison B. Sekuler and Patrick J. Bennett
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Shape Perception 755
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Further Readings
Biederman, I. (1987). Recognition-by-components: A theory of
human image understanding. Psychological Review 94: 115–
147.
Cavanagh, P., and Y. Leclerc. (1989). Shape from shadows. Journal
of Experimental Psychology: Human Perception and Performance
15: 3–27.
Jolicoeur, P. (1992). Identification of disoriented objects: A dualsystems
theory. In G. Humphreys, Ed., Understanding Vision:
An Interdisciplinary Perspective. Cambridge, MA: Blackwell,
pp. 180–198.
Marr, D., and H. Nishihara. (1978). Representation and recognition
of the spatial organization of three-dimensional shapes. Proceedings
of the Royal Society of London Series B Biological
Sciences 200: 269–294.
Rock, I. (1973). Orientation and Form. New York: Academic Press.