The Structure of Cognitive Speed Measures in Old and Young Adults.

The speed hypothesis attempts to explain changes in speed of intellectual functioning with increased age by postulating a central speed mechanism or, in a weaker version, multiple speed mechanisms. In this study the issue of structure of measures of speed was addressed by conducting simultaneous confirmatory factor analyses in two age groups at the level of first order and then at the level of second order factors. Sixteen speed measures were included. The analyses were performed in a sample of 149 elderly adults aged 58 to 73 and in a sample of 147 young adults aged 18 to 33. Five first order factors of speed were found, as hypothesized. A model assuming both invariance of factor loadings and of factor intercorrelations was found to fit well the data. Three second order speed factors were necessary to account for the relationships between the first order speed factors, suggesting that a weak version of the speed hypothesis is correct.