Page 192 - Foundations of Cognitive Psychology : Core Readings

196 Stephen E. Palmer

Figure 8.5
Grouping by synchrony. All else being equal, elements that change their properties at the same time
(as indicated by the arrows) are grouped together.

Figure 8.6
Grouping by common region. All else being equal, elements within the same region of space are
grouped together (A), even when they are farther apart than elements in different regions (B). (After
Palmer, 1992.)

same surrounding contour. Figure 8.6B shows that grouping by common re-
gion is powerful enough to overcome proximity that would, in itself, produce
theoppositegrouping structure.
A third newly proposed principle of grouping is element connectedness:All
else being equal, elements that are connected by other elements tend to be
grouped together. Palmer and Rock (1994) provide a number of demonstrations
of its potency in grouping. An example that is analogous to Wertheimer’s clas-
sic demonstrations is shown in figure 8.7A. The line of equally spaced dots is
strongly grouped when subsets of the dots are connected by additional ele-
ments, such as the short horizontal line segments of this example. Figure 8.7B
demonstrates that element connectedness can overcome even the powerful ef-
fect of proximity.
Wertheimer may not have considered element connectedness as a separate
principle because it could be considered as the limiting case of maximal prox-
imity. However, Palmer and Rock argue for distinguishing connectedness from
proximity for several reasons. First, there is an important qualitative distinction
between actual connectedness and mere proximity. Indeed, this distinction is a