Elementary cognitive processes in choice reaction time tasks and their correlations with intelligence

Today we know that the speed of information processing is correlated with psychometric intelligence, i.e. high intelligence is associated with a fast SIP (as indexed by short RTs in so-called elementary cognitive tasks). Especially in choice RT tasks the following elementary cognitive processes (ECPs) can be distinguished (according to Smith, 1980): stimulus perception, stimulus discrimination, response choice and motoric response. However, it is still unclear which of these processes contributes to the SIP-intelligence relationship. To investigate this question, we devised a new choice RT task that enables one to isolate the above-mentioned ECPs. This so-called stimulus discrimination test (SDT) was administered in two studies (N = 90 and N = 160) together with different intelligence tests and, in Study II, with several other elementary cognitive tests. The results of both studies show that the relationship between elementary cognitive tasks and intelligence seems to be determined mainly by the process of response choice, although in Study II there was also some evidence for the role of stimulus discrimination. These findings are discussed with respect to the mental speed hypothesis of intelligence.