Intelligence and speed of information-processing: A review of 50 years of research

This study reports the results of a large scale literature review of research studying the relationship between intelligence and speed of information-processing. Data from 172 studies, with a total of 53,542 participants, were analyzed to find the mean correlations between a variety of intelligence and mental speed measures. Additionally, effect sizes representing group differences on speeded measures were calculated, and multivariate behavioral genetic (BG) studies reporting genetic correlations between speed of processing and IQ were reviewed. The results indicate that measures of intelligence are significantly correlated with mental speed and that for some measures this relationship shows a trend toward strengthening as the complexity of the speeded tasks increase. Additionally, there are various group differences on mental speed tasks: females and males are quicker than one another on different speeded tasks, and younger adults have shorter (faster) reaction time latencies than older adults and children. Reports comparing whites and blacks on mental speed yield inconsistent results. Finally, BG studies indicate that phenotypic correlations between IQ and mental speed are substantially attributable to correlated genetic factors.