Sleep Loss Hits Extroverts Harder

Nov. 6, 2010— -- Sleep deprivation takes a heavier toll on the performance and alertness of people who are extroverts than it does on their introverted counterparts, according to results of a randomized clinical study.

Extroverts had lower scores on tests of alertness and wakefulness during 36 consecutive hours awake, including a 12-hour period of social interaction, researcher Tracy L. Rupp of Walter Reed Army Institute of Research in Silver Spring, Md., and co-authors reported in the November issue of Sleep.

In contrast, 36 hours of sleep deprivation that included no social interaction had minimal effect on performance or alertness of extroverts or introverts.

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The findings provide insights into interindividual differences in vulnerability to sleep deprivation, particularly interaction between personality traits and social conditions. However, the effect of the interaction was the opposite of what the investigators had hypothesized.

"Although the hypothesized main effects of social condition and personality were not confirmed, the significant interaction between these two factors tends to confirm our primary hypothesis that social experience does significantly affect the ability to resist subsequent sleep deprivation," they wrote in the discussion of their findings.

"But this effect is mediated by individual differences in introversion-extroversion, a personality trait that is believed to reflect general cerebral arousal level."

The findings reflect the investigators' ongoing investigation of Eysenck's theory, which revolves around the concept of cortical arousal as a determinant of introverted or extroverted personality.

According to the theory, social gregariousness and sensation-seeking behaviors arise, at least in part, from lower levels of tonic arousal. Because of their presumed lower level of cortical arousal, extroverts seek out social contact and stimulation to increase brain arousal to optimum levels, the authors noted.