Confusion of group interest and self-interest in parochial cooperation on behalf of a group

People often sacrifice their self-interest for a group to which they belong. even when outsiders are harmed so that the sacrifice has no net benefit. Two experiments (conducted on the World Wide Web) suggest that people do this, in part, because they think that cooperation on behalf of the group is in their narrow self-interest; they show an enhanced self-interest illusion. One experiment found that the self-interest illusion is related to the enhanced tendency to cooperate on behalf of a group when the insiders' gain is the outsiders' loss. A second experiment found that the illusion (and the resulting parochial cooperation) was reduced when subjects were required to calculate all gains and losses.