Perceptual Coherence : Hearing and Seeing

392 Perceptual Coherence
Figure 9.5. The principle of
uniform connectedness first
breaks the visual scene into
enclosed regions. The problem
now is grouping the
discrete regions into objects
(e.g., whether the two small
triangles are part of a larger
triangle and whether the two
rectangular segments are
connected) and creating the
figure-ground relationships.
We perceive the two large
light gray areas as forming a
continuous ground, but again,
that is an inference.
stay with the figure; the boundary shifts from being part of the white rectangle
in front of the black rectangle to being a hole in the black rectangle
in front of a white continuous background. The boundary shifts as a unit; it
does not break apart. 2
The principles for determining which regions become the figure include
the following:
1. Surroundedness: Any region completely surrounded by another usually
is perceived as the figure in front of the surrounding ground.
(Unless, as illustrated in figure 9.6, it is perceived as a hole in an
object, the choice between figure and hole being determined by
other cues.)
2. Size: The smaller region usually is perceived as the figure. It is more
likely that a smaller object will occlude part of a larger one than the
reverse.
3. Contrast: Within a surrounded region, the area with the highest
contrast to the background usually is perceived to be the figure.
2. The same perceptual phenomenon is found for auditory induction. The tone (i.e., the
figure) appears to continue through the noise masker, and the frequency components common
to the tone and masker belong to the tone.