Recent research suggests that individual differences in brain dopamine (DA) functioning may be related to the personality dimension of extraversion. The present study was designed to further elucidate the biological mechanisms underlying behavioral differences between extraverts and introverts. For this purpose, the differential effects of a pharmacologically induced blockade of mesolimbocortical DA D2 receptors on reaction-time performance were investigated in 24 introverted and 24 extraverted subjects. Introverts were found to be much more susceptible to pharmacologically induced changes in D2 receptor activity than extraverts. This finding provides additional experimental evidence for the notion that individual differences in D2 receptor responsivity may represent a neurobiological substratum for the personality dimension of extraversion.
