Recent psychological investigations have left little doubt that considerable mental deterioration takes place with advancing age. The work of the United States Army Psychologists in the last war (22), of Beeson (1), Jones and Conrad (10), Weisenburg, Roe and McBride (21), Sorensen (18), Miles (11, 12, 13, 14), Ruch (17), Thorndike (19), Wechsler (20), Gilbert (7); Cleveland and Dysinger (3) and others makes it apparent that not only do the various mental abilities decline with age, but also that they decline at different rates.