"What you see may not be what you get": Reverse contingency and perceived loss aversion in pigeons.

The reverse-contingency task is a task in which one is given a choice between two rewards, but one receives the larger amount only if one chooses the smaller amount. This task is very difficult for chimpanzees unless the choice is between symbolic representations of the amounts. We found that pigeons can learn this task easily, if the reward amounts are associated with distinctive colors and the choice is delayed by 5 s.