Intelligence and inspection time: Achievements, prospects, and problems.

Ian J. Deary Con Stough I I The purpose of this article is to introduce the inspection- time measure to the wider psychological community. In- spection time is, to date, the only single information- processing index that accounts for approximately 20% of intelligence-test variance. We argue that inspection time, because of its much-replicated correlation with 1Q and its potential for theoretical tractability, has more potential for our understanding of individual differences in cognitive ability than other indexes of human information process- ing. The nature of inspection time and its measurement are described, studies correlating inspection time and IQ- type test scores are summarized, and the difficulties of explaining this correlation are highlighted.