 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.