Gray’s theory offers arguably the best to nowadays neurophysiological explanation of personality. One of its most polemical issues is the relationships between reward sensitivity, which depends primarily on the activity of dopaminenergic brain structures, and personality constructs of Extraversion and Psychoticism. One part of the researchers, including Gray, links the high activity of dopaminenergic brain structures to Psychotism while others connect it to Extraversion. By contrast, the author argues that the high activity of dopaminenergic brain structures, which mediates the activation of behaviour, is typical of both extraverts and high Psychoticism scorers. Meantime, such feature of extraverts as their positive emotionality and sociability might depend on other mechanisms, arguably on the activity of the opiate brain system. This is illustrated by a series of empirical research that shows that the psychometric scales created for measuring behavioural activation can correlate with either Extraversion or Psychoticism depending on whether those who created these scales had considered positive emotionality an attribute of behavioural activation or not. The second series of empirical research demonstrates that under conditions of psychophysiological experiment the scale of behavioural activation (linked to Extraversion) helps detect subjects who show higher electrophysiological manifestation of emotional arousal in a reward situation. The third series of research shows that the scale of behavioural activation linked to Psychotism is one of the strongest predictors of substance use. Extraversion may also be a risk factor but it is also positively related to subjective well-being, educational aspiration, and good relationships with parents which act as protective factors for problem behaviour.