An important component of the neurobiological basis of this measurement system is likely the mesocorticolimbic dopaminergic circuitry. The dopaminergic system (DS) has been for a long time considered the “reward system”. It is also possible, however, that mesolimbic dopamine neurons code for incentive salience in general (Robinson and Berridge, 1993) or stimuli with high motivational impact pertaining to novelty, aversiveness, or deprivation (Bassareo and Di Chiara, 1997) and thus relevant to evaluation on the fitness scale. Among such stimuli, social interactions, attachment, parental behavior, regulated by the vasopressin/oxytocin release, may play an important part, connecting social behavior to addiction liability via common neurobiology (Insel, 2003), which is not necessarily limited to the DS.
