Persons representing the extremes of intelligence cannot be included in the same study unless they are approximately equated on mental age, in which case the relative performances of the extreme groups can provide useful information about the nature of intelligence. (Author/RD)

The author reviews cross-sectional and longitudinal studies on the status of intelligence in the aging, and finds conflicting conclusions: (1) intelligence does decline as persons grow older; (2) only some aspects decline while others improve; and (3) intelligence does not decline. Certain factors are adduced to suggest that such…