The evoked cardiac response as a function of cognitive load differs between subjects separated on the main personality dimensions

We report research on different phasic evoked cardiac responses associated with differences in personality. Heart rate changes were examined in relation to the stable individual difference variables of psychoticism, neuroticism and extraversion. Subjects were divided into different pairs of subgroups on the basis of the measure of their personality dimension scores (above and below the group median). Each subject received 10 innocuous auditory stimuli with randomly varying interstimulus intervals. Stimuli were presented in one of two conditions. In the irrelevant condition there was no task, while in the relevant condition, subjects were required to count the number of stimuli presented. A main effect of condition was obtained in the evoked cardiac response. The initial heart rate deceleration was significantly larger in the irrelevant condition and a later acceleration was significantly larger in the relevant condition. High psychoticism subjects had smaller heart rate changes to the irrelevant stimuli and smaller differences between the relevant and irrelevant conditions than did low psychoticism subjects. High neuroticism subjects, compared with low neuroticism subjects, showed some enhanced cardiac responding to relevant stimuli, but there were no effects of differences in extraversion. The data are discussed in terms of the intensity of stimulus processing (both physical and cognitive) as a factor that may be related fundamentally to stable individual differences in personality.