Distinct visible elements will be grouped to form coherent perceptual organ-
izations if they fulfill certain conditions. The first is similarity. In the first part
of the figure, the black and white blobs can be seen as different subgroups be-
cause of the similarity of color within each group and the contrast between
groups. Similarly, in audition we find that sounds of similar timbres will group
together so that the successive sounds of the oboe will segregate from those of
the harp, even when they are playing in the same register.
The second part of the figure shows grouping by a second factor, proximity,
where the black blobs seem to fall into two separate clusters because the mem-
bers of one cluster are closer to other members of the same one than they are to
the elements that form the other one. It would appear then that the example of
stream segregation would follow directly from the Gestalt law of grouping by
proximity. The high tones are closer to one another (in frequency) than they are
to the low ones. As the high and low groups are moved further away from one
another in frequency, the within-group attractions will become much stronger
than the between-group attractions. Speeding the sequence up simply has the
effect of moving things closer together on the time dimension. This attenuates
the differences in time separations and therefore reduces the contribution of
separations along the time dimension to the overall separation of the elements.
In doing so, it exaggerates the effects of differences in the frequency dimension,
since the latter become the dominant contributors to the total distance.
In both parts of figure 9.11, it is not just that the members of the same group
go with one another well. The important thing is that they go with one another
betterthan they go with members of the other group. The Gestalt theorists
argued that there was always competition between the ‘‘forces of attraction’’ of
elements for one another and that the perceptual organization that came out of
this conflict would be a consequence of the distribution of forces across the
whole perceptual ‘‘field,’’ and not of the properties of individual parts taken in
isolation.
The Gestalt psychologists’ view was that the tendency to form perceptual
organizations was innate and occurred automatically whenever we perceived
anything. It was impossible, they claimed, to perceive sensory elements with-
out their forming an organized whole. They argued that this organizing ten-
dency was an automatic tendency of brain tissue.
Figure 9.11
Illustration of the effects of the Gestalt principles of similarity and proximity on visual grouping.
228 Albert S. Bregman