The impact of the neurotransmitter serotonin on the brain functioning is extensive, and the treatment of a number of psychological disorders involves serotonin in some way or another.
A new experimental study by Crockett and colleagues (2013) examined the influence of serotonin on the social behaviours fairness and justification (retaliation). They did so by conducting a functional neuroimaging study, and the impact of serotonin depletion on the participants’ behaviours was examined.
They found that serotonin had an influence on the reckoning of social value. This means that the enhancement of serotonin levels was associated with a decreased motivation to engage in the punishment of other people. In other words, higher levels of serotonin evokes fairness, and the aversion of hurting others.
In contrast, the depletion of serotonin affects retaliation behaviours, which implies that participants are more likely to punish unfair behaviours directed towards themselves, which can be considered as an antisocial behaviour, since it does not contribute to the maintenance of the group.
Indeed, the depletion of serotonin in humans, as well as in primates, has been associated with aggression and inappropriate (anti)social behaviours, and in fact, it also reduces fairness preferences. Higher levels of serotonin, on the other hand, increase fairness preferences, and decreases antisocial behaviours.
This study emphasizes the impact of serotonin on social and cooperative behaviours, which others studies have shown as well (Depue & Morrone-Strupinsky, 2005), and it can be perceived as a contribution to the understanding of why some people are extremely violent, while others are not.