Age differences in the structure of intelligence - Influences of information processing speed

A battery of widely studied psychometric ability tests, measuring seven primary abilities, was administered to undergraduate students and a cross-sectional sample ranging in age from 43 to 78. The battery included measures of how rapidly individuals could mark answer sheets when provided with booklets containing correct answers to test questions. Confirmatory factor analyses showed that the ability factors could be identified in all age groups, but that the factor structure did not show (metric) invariance of factor loadings across age groups. Factor correlations increased with age, as did the ability tests' communalities, indicating a type of dedifferentiation of the primary ability factor structure. Thurstone's Primary Mental Abilities (PMA) Verbal Meaning Test was shown to have a strong relationship to answer-marking speed, independent of Verbal Ability, and this relationship was higher for older adults. Several ability factors had high correlations with a factor measuring answer sheet speed, and controlling for speed by removing the answer sheet-related variance attenuated the pattern of higher factor correlations for older adults. Findings were consistent with the view that speed of information processing can be both an important correlate of individual differences in rates of intellectual aging and a performance-specific confound that distorts estimates of age-related change in psychometric ability tests. (C) 2001 Elsevier Science Inc. All rights reserved.