Figure 1.

A schematic diagram indicating the procedure for each trial of an inequity test. Two primates (P1 and P2) are tested in a pair. For each condition (see Table 1, columns 1 and 2), the primates must sequentially perform a task with the experimenter (typically a token exchange; Table 1, column 3) in order to receive a food reward (Table 1, column 4; see full description of each condition in column 5). An arrow indicates the order in which the object (token or food) moves between the experimenter (E) and the primates in each step of the trial. In all studies in my laboratory, primates are seated side-by-side. Monkeys are separated by a mesh barrier which they can reach through while apes are not separated. The details of the exchange task and the foods given to each primate are determined by the test condition; for details see Table 1.