"Altruistic" Behavior in Rhesus Monkeys

Previous work in our laboratory(1) had demonstrat-ed that most rhesus monkeys refrained form operating a device for securing food if this caused another monkey to suffer an electric shock. The present experiments were designed to investigate some of the determinants of this altruistic behavior. EXPERIMENTAL METHOD A 5 X 5 X 2 ft. masonite and plexiglass box was divided in the middle by a half-silvered screen that blocked vision only from the right (stimulus) to the left (operator) compartment. The latter was equipped with red and blue signal lights, two chains suspended from ceiling microswitches, a food tube and a water cup; the right compartment was bare except for floor and wall grids attached to a Grason-Stadler E6070B constant cur-rent shock source and scrambler. Eight male and 7 female feral rhesus monkeys (Os) were separately trained in the operator compartment to secure a 0.7 gm. pellet of food by pulling one chain in response to a red light and the other chain to a blue one, each of 5 sec. duration and occurring in random order at irregular intervals ranging from a mean of 15 sec.; this training was continued until the responses were 90% correct with less than 20 unsignalled reactions in 2 con-secutive sessions. A stimulous animal (SA) was then placed in the right compartment for 3 sessions while the O continued to feed on signal; however, on the 4th day one of the chanins was programmed also to administer a 3 sec., 5 ma high-frequency shock to the SA. Each O was run with a given SA until, again in 2 consecutive sessions, either (i), the O selected the non-shock