Modelling the structure and development of g

This study investigated the structure and development of processes involved in g. One hundred and forty children, about equally drawn among primary school grades 1–6 were examined by four types of Stroop-like speeded tasks addressed to processes of increasing complexity (i.e., speed of processing, perceptual discrimination, perceptual control, and conceptual control) and tasks addressed to working memory, information integration, and reasoning. Structural equation modelling showed that these processes are hierarchically organized so that the processes at each subsequent higher level in the hierarchy include the processes of all previous levels together with processes specific to this level. Speed of processing and perceptual control were the most powerful predictors of the state of processes residing higher in the cascade. Analysis of variance showed that all of these processes improve systematically with age and that developmental differences in higher level processes are partly accounted for by lower level processes and by factors germane to themselves. The implications of these findings for the general theory of intelligence are discussed.