Negative Behavioral Contrast in Capuchin Monkeys (Sapajus sp.)

A capuchin monkey will accept a preferred food in exchange for tokens if a conspecific also exchanges tokens for the preferred food; but he will reject a less-preferred food if the conspecific exchanges tokens for preferred food. These rejections are usually interpreted as a case of an inequity aversion based on a precursor of a sense of justice. An alternative hypothesis proposes that it is the contrast between the types of food reinforcement...