Turning from illusions of suggestion, shape and size, another field of peculiar sensory illusions is found in color aberration. Some colors look closer than others. For instance, paint an object red and it seems nearer than it would if painted green. [Sidenote: _What Colors Look Nearest_] Aside from the obvious uses to which these sense-illusions can be put, they form the basis for a number of psychological experiments to test the abilities of persons in many ways. Here is a test which deals with the range of attention. If you desire to discover the capacity of any person to pay attention to unfamiliar questions or subjects which might at some future time have great importance, try this test. Have a piece of pasteboard cut into squares, circles, triangles, halfmoons, stars and other forms. Then write upon each piece some such word as hat, coat, ball or bat. The objects are then placed under a cloth cover and the subject to be examined is told to concentrate his attention on the shapes alone, paying no attention to the words. The cloth is lifted for five seconds and then replaced. The subject is then told to draw with a pencil the different shapes and such _words_ as he may chance to remember. The experiment should then be repeated, with the injunction to pay no attention to the shapes but to remember as many words as possible, and write them down on such _forms_ as he may happen to recall. [Sidenote: _Testing the Range of Attention_] Of course, the real object is to determine whether the subject will see more than he is told, or whether he is a mere automaton. The result will tell whether his attention is of the narrow or broad type. If it be narrow, he will see only the forms in the first case and no words, and in the second case he will remember the words but be unable to recall the shape of the pieces of cardboard. [Sidenote: _A Guide to Occupational Selection_] His breadth of attention will be shown by the number of correct forms and words combined which he is able to remember in both cases. In other words, this will measure his ability to pay attention to more than one thing at a time. Other things being equal, the narrow type of attention belongs to a man fitted for work as a bookkeeper or mechanic, while the broad type of attention fits one for work as a foreman or superintendent or, lacking executive ability, for work requiring the supervision of mechanical operations widely separated in space. [Sidenote: _Test for Attention to Details_] The ordinary man sees but one thing at a time, while the exceptional man sees many things at every glance and is prepared to remember and act upon them in emergency.