A WAIS longitudinal study of cognitive development during the life span from ages 50 to 70

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Abstract
A sample of 141 subjects born in 1914 was tested with the Wechsler Adult Intelligence Scale (WAIS) at the ages of 50, 60, and 70. Results showed a relatively moderate decline in test scores between successive examinations. For most subtests the decline was larger between 60 and 70 than between 50 and 60, and also larger for the Performance subtests than for the Verbal subtests (the total fall in Performance IQ was 7.2, and the total fall in Verbal IQ was 3.2). Seventy‐three males showed a larger decline than 68 females in Performance and Full‐Scale IQ, but the fall in test scores was not systematically related to educational background or initial IQ group. Further analysis provided evidence for a terminal drop hypothesis. The study demonstrated strikingly high retest stability of the WAIS IQ (a 20‐year retest coefficient of 0.90 for the Full‐Scale IQ).