The Aging Dimension: A Factorial Analysis of Individual Differences with Age on Psychological and Physiological Measurements

Abstract

A battery of 25 physiological, ability and personality measures, most of which were expected to vary with age, were administered to a sample of 102 males and females evenly covering the age span of 20 to 70 years. Five factors were extracted from the 25 x 25 correlation matrix by the centroid method and rotated into an approximation to oblique simple structure. A single general aging factor was obtained, loading 19 of the 25 measures and accounting for almost all the variance of age. It was not possible to break this general factor down, that is, to unload more of its variance onto the minor factors. We must conclude that, at the level of this analysis, aging occurs along a single dimension, measured best by blood pressure, lens accommodation and sound threshold and less well by ability and speed tests. Factor 2 lent credence to the generality of the aging factor. Factor 2 was an unambiguous general ability factor approximately orthogonal to the aging factor and having no age loading. Because of the lack of a hyper-plane, the positioning of the aging factor was inexact. A further factor analysis should include a sufficient amount of variance in the hyper-plane to enable the rotation of the aging factor to a unique position.