The neurobiological mechanisms associated with affiliation, that Depue & Collins argue are a central component of extraversion are not specified in their model. In addition, only the involvement of the prefrontal cortex in extraversion is discussed, although recent evidence suggests that activity associated with additional cortical regions may be related to this trait. Finally, the assumption that neurobiological mechanisms underlie or play a causal, and therefore, more fundamental role than psychological constructs in the trait is challenged.