Replicating the movement time–extraversion link…with a little help from IQ

Doucet and Stelmack [Doucet, C., & Stelmack, R. M. (1997). Movement time differentiates extraverts from introverts. Personality and Individual Differences, 23, 775–786] report the most recent finding of a negative correlation between movement time and extraversion, and provide a detailed examination of the effect. The present study examined this association with particular emphasis on the moderating role of intelligence. To this end, 68 adult male subjects completed tests of extraversion and intelligence and a set of three reaction time tests. Although the zero-order correlation between extraversion and movement time was nonsignificant (but in the predicted direction), after partialling out FSIQ, the predicted significant negative correlation was observed, r=−0.25, P<0.05. Effects for reaction time were nonsignificant. Evidence was also found for a curvilinear effect whereby ambiverts are the slowest movers, extraverts are the fastest, and introverts fall in the middle. These results are interpreted as showing the importance of examining elementary motor processes in addition to higher-order psychological functions in attempting to explain individual differences in extraversion.