Page:Popular Science Monthly Volume 51.djvu/667

Rh readily and accurately, to retain and reproduce visual impressions, and to identify new impressions similar to others recently experienced, is detected, These experiments test in a way at least the processes of attention, perception, retention, and comparison or reason; and because of their simplicity, not being complicated with other factors, it is comparatively easy to detect varying power on the part of the pupil.

Space will not permit a detailed statement of the results of these studies, but it may be said in summary that after two and a half hours' work in the schoolroom almost all pupils show a decrease in intellectual power. Reaction time is considerably lessened—the pupil can not perceive and react so quickly or with such surety. He can not discriminate colors with such keenness. If in the morning he can detect a gramme pressure upon the back of the hand, he now requires two grammes or more in order to receive an impression. If when he is refreshed he can detect two points upon the back of the hand thirty millimetres apart, they must be separated considerably in order to be detected as two when he is in a state of fatigue. In a test of physical control the hand will be found much less steady after a few hours of mental labor, as may be seen by examining one's handwriting with a magnifying glass. If the pupil endeavor to perform some difficult task requiring great co-ordination of the different parts of the body, as in directing a light rod upon a small point a few feet away but yet within easy reach, or in threading a fine needle, the influence of fatigue is easily observed. In the laboratory a device is used whereby an electric bell is rung when a given point is not touched. In testing a pupil in this way it has often been found that he can not only not touch