Geography Reference
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Figure 11.5
Two versions of the Kanizsa triangle illusions (Adapted from Kaiser, 2007) www.
yorku.ca
are meant to be disconnected can appear to be very strongly connected. There are many
examples of optical illusion that illustrate this and one of the simplest is the Kanizsa triangle
(Figure 11.5). The white triangle is seen even with drastic miss-alignments of the angles and
large separations of the end points. The way the human visual system is able to interpret
a triangle is understood through these higher-level 'contour' cells that signal a continuous
line even when there are disconnected edges.
Other illusions are now resolvable with better understanding of the neurological wiring.
Figure 11.6 illustrates the spatial location variation within our visual system, with a device
called the Herman grid illusion. There is a higher degree of accuracy for our vision at the
central area of focus. When you focus on a small part of the grid of squares, the edges of
the neighbouring squares are very sharp, whereas at the periphery grey dots appear between
the squares. The intermediary cells have smaller and larger receptive fields at the focus
and periphery of vision, respectively, and the process of convolution involved is a plausible
explanation.
Figure 11.6
Version of the Herman grid illusion (Adapted from Kaiser, 2007) www.yorku.ca
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