Abstract
BackgroundReaction time (RT) has played a prominent part in research on mental ability for over a century. Throughout this time a number of questions have been repeatedly posed: what is the relationship of RT to general mental ability, and is this the same for simple and choice RT? Does the relationship change with age? How important is RT variability compared with mean values? Here we examine these questions in three population representative cohorts. MethodsParticipants were drawn from the West of Scotland Twenty-07 study, a longitudinal population based study designed to investigate socially structured health inequalities. At the fourth wave of data collection, part I of the Alice Heim 4 (AH4) test of general intelligence was administered, and reaction times were measured using a portable device. Means and standard deviations were recorded for simple and 4-choice reaction time. Full data were available for 2196 participants, comprising 714 aged 30years, 813 aged 50, and 669 aged 69. ResultsCorrelations of simple RT means with AH4 scores were −0.27, −0.30 and −0.32, for age 30, 50 and 69, respectively; and −0.44, −0.47 and −0.53 for 4-choice RT. The underlying relationships showed evidence of non-linearity, particularly for simple RT, with stronger association at lower AH4 scores. This was more pronounced with age. RT variability was correlated with the mean at 0.57, 0.57, 0.58 for simple RT; and 0.53, 0.53, 0.47 for choice RT. Residuals from regressing the RT variability on the mean showed no association with AH4 in the case of simple RT but a weak association for choice RT which decreased with age. ConclusionsThere is a strong correlation of RT means with general mental ability which increases with age. The underlying relationship is complex for SRT. RT variability shows little association with mental ability when its dependence on the mean is removed. Combining samples with disparate ages may overestimate the association.
Highlights
Individual differences in reaction time were already being observed in the early 19th century (Brebner & Welford, 1980; Jensen, 2006) and have played a part in research on human mental ability for well over a century
Given that simple reaction time (SRT) and CRT have different relationship to IQ and show different patterns of ageing, we hypothesized that the pattern of correlations might differ with age. To test this hypothesis we present the correlations between Reaction time (RT) parameters – means and standard deviations – and scores on the Alice Heim 4 test of general mental ability in three large population-representative cohorts aged around 30, 50 and 69 years
We address a number of questions with respect to SRT and CRT: How strong is the correlation between intelligence and RT parameters? Does the relationship between them vary with age across adulthood? Is the underlying relationship linear? We examine the effect of combining the data from different ages
Summary
Individual differences in reaction time were already being observed in the early 19th century (Brebner & Welford, 1980; Jensen, 2006) and have played a part in research on human mental ability for well over a century. From the earliest days psychologists realised that RT might be used as a measure of mental speed (which might be termed ‘processing speed’) They had differing expectations of whether a purified measure of speed, such as simple reaction time (SRT), would be related to more general, higher-level mental ability. Reaction time (RT) has played a prominent part in research on mental ability for over a century Throughout this time a number of questions have been repeatedly posed: what is the relationship of RT to general mental ability, and is this the same for simple and choice RT? The underlying relationships showed evidence of non-linearity, for simple RT, with stronger association at lower AH4 scores
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