Perception Starts at the Receptors: Bottom-Up Processing • 51BOTTOM-UP PROCESSING: BEHAVIORAL
The idea that neurons fi re to individual features of a tree suggests that perhaps our
perception of the tree is created by combining the information provided by the fi ring
of many feature detectors. A behavioral approach to this idea that perception can be
created by combinations of individual features has been proposed by Irving Biederman
(1987). His idea, called recognition-by-components (RBC) theory, proposes that we
perceive objects by perceiving elementary features like those in ● Figure 3.3a, called
geons. Geons are perceptual building blocks that can be combined to create objects, as
shown in Figure 3.3b.
One of the characteristics of object perception, according to RBC, is that we can
recognize an object if we are able to perceive just a few of its geons. For example,
Biederman showed that an airplane that has a total of nine geons (● Figure 3.4a) was
recognized correctly about 78 percent of the time even if only three geons were present
(Figure 3.4b), and 96 percent of the time if six geons were present.
We can also perceive objects even if portions of the geons are obscured, as shown
in ● Figure 3.5a. The reason you can tell this is a fl ashlight, according to RBC, is that
you are able to make out its geons. This is an example of the principle of componen-
tial recovery—if we can recover (see) an object’s geons, we can identify the object.● (^) FIGURE 3.3 Left: Some geons. Right: Some objects created from the geons on the left.
The numbers on the objects indicate which geons are present. Note that recognizable
objects can be formed by combining just two or three geons. Also note that the relations
between the geons matter, as illustrated by the cup and the pail. (Source: Adapted from
I. Biederman, “Recognition-by-Components: A Theory of Human Image Understanding,” Psychological Review,
24 , 2, 115–147, Figures 3, 6, 7, and 11, Copyright © 1987 by the American Psychological Association. Reprinted
by permission.)
(a) Geons (b) Objects
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●FIGURE 3.4 An airplane represented (a) by nine geons and (b) by three geons.
(Source: From I. Biederman, Computer Vision, Graphics and Image Processing, p. 73. Copyright © 1985 by Irving
Biederman. Academic Press, 1985. All rights reserved. Reproduced by permission of Elsevier, Ltd.)
(a)(b)
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