Depue & Collins propose that extraversion should be separated from the impulsivity-constraint dimension of personality, and that the VTA dopamine system is the primary engine of extraversion. Although their focus is on personality traits, it may be useful to consider the evidence on psychological state changes, related both to affective arousal and to drug effects. This evidence shows that there are inherent relations between extraversion and impulsivity-constraint, and that there are influences of dopamine on impulsivity-constraint that are not consistent with the Depue & Collins model. Increased positive affect leads to increased extraversion, and this is associated with more impulsivity and less constraint. The evidence on drug effects shows that greater dopaminergic control is associated with more constraint, and with anxiety and vigilance rather than positive affect.