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

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Abstract

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.

Section snippets

Method

An extensive literature search from 1955 to 2005 was completed with the assistance of electronic search engines PSYCARTICLES and PSYCINFO, as well as relevant scholarly books and journals. Paired combinations of the following search terms were used electronically: “reaction time”, “response time”, “mental speed”, “speed of processing”, “speed of short-term memory processing”, “speed of long-term memory retrieval”, “chronometric ability”, “inspection time”, “task complexity”, “intelligence”,

Results

The overall sample size of studies included in this review was 53,542. Individual study sample sizes ranged from ten to 10,535 participants, with 278.9 participants as the mean sample size (s = 963.12). The inter-quartile ranges were as follows: 25th = 49.25, 50th = 82, and 75th = 177. Of those studies that reported the sexes of their subjects, the average sample had between zero and 3811 female participants with a mean of 103.7 (s = 341.38), and between zero and 3674 male participants, with a mean of

Discussion

The results of this review indicate that diverse measures of mental speed are significantly correlated with measured intelligence. There is a trend – among some mental speed tasks – for more complex measures to be more highly correlated with intelligence but this effect is not evident for all tasks. The results also reveal that mental speed often (though not always) correlates more strongly with gf than with gc. This is particularly evident for novel mental speed tasks – many of which fell into

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