mental context, and if the disk of figure 21.8 is removed to reveal two bars, the
infant registers surprise (as measured by breathing and heart rate increases).
We will discuss more on early infant studies later in this chapter.
The Italian psychologist Gaetano Kanizsa has come up with a number of in-
teresting examples of perceptual completion orsubjective contours. Figure 21.9
demonstrates this phenomenon: it is difficult not to see a white triangle located
at the center of the figure, although no such triangle actually exists. In the
external world, the most probable cause for the improbable alignment of the
objects is that a white triangle is lying on top of these objects, covering some
and partially masking others.
This phenomenon can also be demonstrated in the auditory domain. Al
Bregman has demonstrated this with sinusoidal tones that sweep up and down
Figure 21.7
Continuation. We would normally assume one bar beneath the disk.
Figure 21.8
Another possible explanation of figure 21.7.
Figure 21.9
More continuation, and some symmetry.
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