Extraversion, attention, and startle response reactivity

The present study investigated the impact of directed attention tasks performed by introverts and extraverts, using the brainstem startle eyeblink response as a measure of automatic reactivity. Participants (23 introverts and 24 extraverts) were instructed to either attend to a startle-eyeblink-eliciting acoustic noise pulse (90 or 105 dB) or to a drawing of animals, or to ignore all stimuli, while their eyeblink reflex to the noise pulse was measured. In the no-task condition, introverts were generally more reactive than extraverts. When attention was directed to the startle-eliciting stimulus, startle response amplitude was potentiated in both introverts and extraverts. When attention was directed to a visual task, acoustic startle reactivity was reduced for introverts, but not for extraverts. Therefore, introverts were more able to focus their attention, and were less distractible than extraverts. These data support previous findings of a narrower focus of attention in introverts than in extraverts, based on differences in arousal as a function of extraversion.