Homo economicus
The emerging science of "neuroeconomics" suggests that there are serious shortcomings in the conventional theories of economic rationality. Rational economic decision making has been shown to produce high levels of cortisol, epinephrine and corticosteroids, associated with elevated levels of stress. It seems that the dopaminic system is only activated upon achieving the reward, and otherwise the "pain" receptors, particularly in the pre-frontal cortex of the left hemisphere of the brain show a high level of activation. Serotonin and oxytocin levels are minimised, and the general immune system shows a level of suppression. Such a pattern is associated with a generalised reduction in the levels of trust. Unsolicited "gift giving", considered irrational from the point of view of "Homo economicus", by comparison, shows an elevated stimulation of the pleasure circuits of the whole brain, reduction in the levels of stress, optimal functioning of the immune system, reduction in cortico-steroids and epinephrine and cortisol, activation of the substantia nigra, the striatum and the nucleus acumbens (associated with the placebo effect), all associated with the building of social trust. Mirror neurons result in a win-win positive sum game in which the person giving the gift receives a pleasure equivalent to the person receiving it. This confirms the findings of anthropology which suggest that a "gift economy" preceded the more recent market systems where win-lose or risk-avoidance lose-lose calculations apply.