Pain perception and extraversion.

Abstract

Eysenck's ( 1960) theory of personality indicates a positive relationship between Extraversion and the inhibition of stimulation. Ss high on Extraversion should, accord~ng to this theory, have higher thresholds for pain and greater tolerance of pain than low Ss H~gh scorers should, in other words, interpret a given amount of stimulation as less painful than would low scorers. Haslam (1967), using radiant energy as the pain-inducing stimulus, found that high scorers had significantly higher pain thresholds than low scorers. She did not find sex differences for pain threshold with either high or low group. The current study was undertaken to examine the relationships between Extraversion and the initial perception of pain, and between sex and the initial perception of pain, using electric shock as rhe pain-inducing stimulus. Ss were 20 male and 20 female undergraduate students who scored at least 1 SD above (high Extraversion) or below (low Extraversion) the mean on an Extraversion test' which had previously been standardized on 2500 undergraduate students. S's initial pain-perception level was determined by administering an increasing series of electric shocks to S's right index finger. S was asked to indicate the first shock felt and the first shock perceived as painful. The pain-perception level was defined as the difference, in volts, between these two shocks. High and low Extraversion males had mean initial pain-perception levels of 29.8 and 27.7 v, respectively, while high and low females had mean pain-perception levels of 18.8 and 19.8 v, respectively. An analysis of variance showed no significant differences in painperception level as a function of Extraversion for either males or females. The over-all sex difference was significant = 11.01, P < .01). The lack of a systematic relationship between Extraversion and pain-perception level does not seem to support Haslam (1967). Perhaps this discrepancy results from the current study's use of American Ss where Haslam used European Ss. As Mann (1958) suggests, different cultural backgrounds may yield varied behavioral manifestations of Extraversion. An alternate explanation may be found in Haslam's use of continuous stimulation, causing the high scorers to inhibit the stimulation after sufficient build-up. The current study used a series of discrete administrations of the stimulus. Note also, Haslam used the Maudsley Personality Inventory and this study an original device. The sex difference found in the current study also seems not to support Haslam. This discrepancy may be due to the differing physiological effects of the two stimuli used to induce pain. Since the pain-threshold level is much closer to the tissue-damage level with radiant energy than with electric shock, a ceiling effect may well have obscured sex differences in Haslam's study.