In vocabulary, comprehension, and arithmetic only a slight difference is found between the scores made by people in their thirties, the period when their abilities in these areas are highest, and the scores made by people 70 years old.
This special study of older people, supported by the Committee on Human Development, University of Chicago, and bythe U. S. Public Health Service, was carried out in Kansas City concurrently with the national standardization of the same intelligence test for adults 16 to 64 years of age.
For performance, maximum scores are attained by people in their twenties; performance falls off after age 3o with gradual decrements up to age 70, and with marked lowering after that age. Performance tests place a premium on visual acuity, speed, and manual dexterity. Substantial retention of verbal and communication abilities far into old age, is of special significance and is likely to have considerable practical importance in shaping attitudes about and planning programs for older people.