Perceptual Coherence : Hearing and Seeing

378 Perceptual Coherence
Figure 9.2. Examples of the classic Gestalt grouping principles. A sequence of
equally spaced dots will be subjectively grouped into groups of two or three, depending
on the spacing between the dots (A). Dots can be grouped into pairs on the basis
of physical proximity (B), similarity in brightness, size, or another feature (C), common
fate in movement (D), or good continuation along smooth trajectories (E). Dots
will tend to be grouped if they are connected in some way, even though they differ in
size and brightness (F). All of these Gestalt principles also apply to sounds. For example,
a sequence of isochronous sounds will be grouped into twos or threes (subjective
rhythms). The term subjective was chosen because there was no physical
property to account for the grouping. It was an unfortunate choice because all of
these groupings are subjective: Elements merely follow each other in space and time.
target segments increased in luminance at the same time as the remaining
part of the checkerboard decreased, and vice versa. The outof-phase
modulations segmented the elements in the linear segment
from the rest of the checkerboard and permitted the observers to
determine if the linear target region was horizontal or vertical. In
similar fashion, Alais, Blake, and Lee (1998) found that correlated
contrast changes, even in opposite directions, bind Gabor-like blackand-white
patterns together. Another example of common fate is coherent
amplitude or frequency modulation. If parts of an auditory or
visual scene undergo correlated changes (e.g., musical vibrato), it is
likely that those parts will be combined into one object.
5. Temporal synchrony: Elements that undergo simultaneous and coherent
changes in time are grouped together (e.g., S.-H. Lee & Blake,