Chapter 6 Sensation and Perception 197of objects, from tools to animal predators to
chairs, and so far have found no other specialized(^) areas (Downing et al., 2006). This is understand-
able, because the brain cannot possibly contain
a dedicated area for every conceivable object. In
general, the brain’s job is to take fragmentary
fact was first demonstrated by David Hubel and
Torsten Wiesel (1962, 1968), who painstakingly re-
corded impulses from individual cells in the brains
of cats and monkeys. In 1981, they were awarded
a Nobel Prize for their work. Hubel and Wiesel
found that different neurons were sensitive to dif-
ferent patterns projected on a screen in front of an
animal’s eyes. Most cells responded maximally to
moving or stationary lines that were oriented in a
particular direction and located in a particular part
of the visual field. One type of cell might fire most
rapidly in response to a horizontal line in the lower
right part of the visual field, another to a diagonal
line at a specific angle in the upper left part of the
visual field. In the real world, such features make
up the boundaries and edges of objects.
Since this pioneering work was done, scien-
tists have found that other cells in the visual sys-
tem have even more specialized roles. A group of
cells at the bottom of the cerebral cortex responds
much more strongly to faces than to objects—
human faces, animal faces, even cartoon faces.
Evolutionary scientists note that a facility for
deciphering faces makes sense because it would
have ensured our ancestors’ ability to quickly dis-
tinguish friend from foe, or in the case of infants,
mothers from strangers. Another area, a part of
the cortex near the hippocampus, makes sure you
understand your environment. It responds to im-
ages of all kinds of places, from your dorm room
to an open park, and does so far more strongly
than it does to objects or faces. A third region, a
part of the occipital cortex, responds selectively to
bodies and body parts much more strongly than to
faces or objects—and more strongly to other peo-
ple’s bodies than to your own (Kanwisher, 2010).
But there are limits on such specialization.
Researchers have studied 20 different classes
Get Involved! Find Your Blind Spot
A blind spot exists where the optic nerve leaves the back of your eye. Find the blind spot in your left eye
by closing your right eye and looking at the magician. Then slowly move the book toward and away from
yourself. The rabbit should disappear when the book is between 9 and 12 inches from your eye.
Cases of brain damage support the idea that particular
systems of brain cells are highly specialized for identify-
ing important objects or visual patterns, such as faces.
One man’s injury left him unable to identify ordinary
objects, which, he said, often looked like “blobs.” Yet he
had no trouble with faces, even when they were upside
down or incomplete. When shown this painting, he could
easily see the face but not the vegetables comprising it
(Moscovitch, Winocur, & Behrmann, 1997).