Given a situation where there is food available for shared consumption and where the food consists of groups of single items (Dim Sum or Hot Wings). The Dim Sum Effect is when the food is depleted to the point that every group of food has one item remaining. At this point, the rate of items eaten stops and with great reluctance the remaining individual items are eaten only after the person taking the item asks nearly everyone in the group whether they want the final item. If there are multiple types of item in a group, the food will deplete to the point that one of each type remains (wings vs drumsticks).

This is proof that altruism is a basic human behaviour.