]

Filled spaces look larger than empty ones because the eye
unconsciously stops to look over the different parts of the filled
area, and we base our estimate upon the extent of the eye movements
necessary to take in the whole field. Thus the filled square in
Figure 5 looks larger than the empty one, though they are of equal
size.

[Illustration: FIG. 5.]

White objects appear much larger than black ones. A white square
looks larger than a black one. It is said that cattle buyers who
are sometimes compelled to guess at the weight of animals have
learned to discount their estimate on white animals and increase
it on black ones to make allowances for the optical illusion.

[Illustration: THIS MAN AND THIS BOY ARE OF EQUAL HEIGHT, BUT
ASSOCIATION OF IDEAS MAKES THE MAN LOOK MUCH THE LARGER]

[Sidenote: _Use of Illusions in Business_]

The dressmaker and tailor are careful not to array stout persons
in checks and plaids, but try to convey an impression of sylph-like
slenderness through the use of vertical lines. On the other hand,
you have doubtless noticed in recent years the checkerboard and
plaid-covered boxes used by certain manufacturers of food products
and others to make their packages look larger than they really are.

The advertiser who understands sensory illusions gives an impression
of bigness to the picture of an article by the artful use of lines
and contrasting figures. If his advertisement shows a picture of a
building to which he wishes to give the impression of bigness, he
adds contrasting figures such as those of tiny men and women so that
the unknown may be measured by the known. If he shows a picture of a
cigar, he places the cigar vertically, because he knows that it will
look longer that way than if placed horizontally.

[Sidenote: _Making an Article Look Big_]

A subtle method of conveying an idea of bigness is by placing
numbers on odd-shaped cards or blocks, or on any blank white space.
The object or space containing the figures always appears larger
than the corresponding space without the figures.

This fact has been made the basis of a psychological experiment to
determine the extent to which a subject's judgment is influenced by
suggestion. To perform this experiment cut bits of pasteboard into
pairs of squares, circles, stars and octagons and write numbers
of two figures each, say 25, 50, 34, 87, etc., upon the different
pieces. Tell the subject to be tested to pick out the forms