Effects of extraversion and mental arithmetic on heart-rate reactivity.

The purpose of the present study was to examine the effect of extraversion and task difficulty on heart-rate reactivity. 15 extraverts and 15 introverts as identified by their scores on the Eysenck Personality Inventory completed mental arithmetic problems of three levels of difficulty. Two-way analysis of variance indicated that heart-rate reactivity increased as task difficulty increased. Also, introverts showed larger heart-rate reactivity to the task than extraverts. The present findings partially support Eysenck's physiological theory of extraversion in that introverted subjects were more aroused by the mental arithmetic task; however, the factors which produce such a difference are unclear.