Page:Popular Science Monthly Volume 79.djvu/93

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PSYCHOLOGY OF MENTAL DEFICIENCY
89
Fig. 7. An Experiment in Action with the Ergograph.
Mental Age Capabilities Class
8 years, Errands. Light work. Makes beds. Low Moron.
9 years, Heavier work. Scrubs, mends, lays bricks, cares for room with simple furniture.
10 years, Good institution helpers. Routine work. Middle
11 years, Fairly complicated work with only occasional oversight.
12 years, Uses machinery. Cares for animals. No supervision. Can not plan. High
Figs. 8 and 9. Ergograms. Records of a normal man and of a defective boy, the latter showing characteristic irregularities.

The ergograph was devised by Mosso, an Italian psychologist, and is used to measure muscular fatigue. A weight is lifted with one finger every alternate second until the muscle is tired out. Each lift is recorded on a vertical line and the sum total of lifts and lengths of lines are indicative of muscular action and voluntary control.

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