Personality, arousal theory and the relationship to cognitive ability as measured by inspection time and IQ

It has been suggested that the association between inspection time and intelligence test scores is mediated by personality/temperament (Howe, 1990). Personality, and in particular the trait of extraversion, has been implicated in IQ performance, and based on differential nervous system arousal, Robinson (1989) has proposed a quadratic relationship between extraversion and IQ. The aims of the present study were to investigate whether personality mediates the correlation between inspection time and IQ, and to test the prediction by Robinson that ambiverts (moderate neural arousal) would score higher on IQ tests than extraverts or introverts. 237 pairs of monozygotic and 297 pairs of dizygotic adolescent twins completed a line discrimination task to measure inspection time, the Multidimensional Aptitude Battery (IQ), and the Junior Eysenck Personality Questionnaire. Correlations between personality and cognitive measures were significant for the extraversion––IQ association, but not for any other personality dimensions, and hence no mediating role of personality in the inspection time––IQ relationship was indicated. A test of mean effects of extraversion on cognitive measures did not support Robinson’s hypothesis, as introverts tended to outperform ambiverts rather than the reverse. A psychophysiological test of the association between personality and arousal was suggested for future research.