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Performances on the Benton Visual Retention Test were collected for 894 men 17 to 96 years of age between 1960 and 1976 and were analyzed using slopes to estimate time-of-measurement effects. For each of the nine birth cohorts and eight age groups, performance (errors) was plotted on calendar time. Comparisons of the within-birth-cohort slopes showed an increase in slope with age (rho = 0.92); earlier born (older) cohorts had larger slopes indicating increased errors per year. Comparisons of within-age-group slopes showed no difference among age groups. Slopes of four of the five oldest cohorts were larger (p less than .05) than the common age-group slope. Whether the common age-group slope was a secular effect, a cohort effect, or some combination of the two, the data were consistent with age changes in performance late in life confirming longitudinal results of direct measures of change previously reported.
David Arenberg (Fri,) studied this question.