Our sense organs 45

– The distances between the arrow tips are
equal. But the directions in which they point
make them appear unequal (illusion of length).
– The second row of figures contains two
equal-sized circles which nevertheless appear
to be different in size (illusion of size).
– The two sets of parallel lines seem to converge
or be crooked (illusion of direction).
– In the lower part of the diagram the circle as
well as the square seems to be distorted (illusion
of shape).
In Figure 2 we see three men walking along a
street. The person in front seems to be the tallest
one, and the one in the rear the shortest. This is
an illusion, since all three of them are the same
height. The surrounding perspective lines make
them appear to be of different sizes.
The three diagrams in Figure 3 do not mislead our
senses, but, in contrast to Figures 1 and 2, they
confront our perception with more than one
possible interpretation:
The semi-opened book can either be seen from
the inside or from the outside.
The staircase can either be seen as ascending
steps, or as viewed from the underside.
The cubical block is even more complex, since
there are three possible ways of “seeing” it.
Figure 2: Are these three men the
same size? (Example of an optical
illusion).
Figure 3: Illusions of perception. Each of
these three geometric figures can be interpreted
in more than one way.
Figure 4: Young girl or old lady?
(Example of an illusion of
perception).
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