Strategic behavior in monkeys

In a recent paper, Lee et al. examined adaptive decision-making processes by training monkeys to play a competitive game against a computer programmed to play using various strategies. They found that the monkeys' responses were sensitive to the computer's strategies and consistent with reinforcement learning. Research such as this strongly complements current research in behavioral economics. We propose some potential future directions for this work, and put forward conjectures about what might be learned about decision-making in humans.     

Second-order avoidance behavior in monkeys

Two monkeys were trained on a three-component multiple schedule using discrete trials. In one component (food), a response terminated a red stimulus and produced food and S(Delta). In the second component (avoidance), a response terminated a green stimulus and avoided shock. In the third component (optional), a response terminated a blue stimulus and produced S(Delta). The consequence of not responding in the blue stimulus, however, was the production of either a food or an avoidance trial. Manipulation of these consequences showed that when food trials were available only a small percent of the time after optional trials, the subjects tended not to respond in the blue, even though this led to an increase in the total number of avoidance trials per day. If only avoidance trials followed as a consequence of not responding in the optional component, the animals terminated the blue stimulus and avoided the avoidance trials. Throughout the experiment both subjects maintained consistently low shock rates (about 10 per day) and these were not affected by the various manipulations. The data suggest that a stimulus associated with avoidance can be a conditioned aversive stimulus and will maintain a more remote avoidance response under certain conditions.     

Measurement of social dominance in squirrel monkeys

Several laboratory methods for measuring social dominance in squirrel monkeys are described.     

Shaping avoidance behavior in restrained monkeys

Lever-pulling avoidance behavior of 24 monkeys was actively shaped with a manual shock-control box and a closed-circuit TV system. A negative reinforcement procedure was used wherein a periodically occurring body shock was postponed each time the subject moved toward the lever. All subjects were trainable with this method, two-thirds of them in fewer than five, 1- to 2-hr sessions. Negative reinforcement was more effective than a punishment procedure.     

Early social experience and responses to visual social stimuli in young monkeys

Juvenile stumptailed macaques (Macaca arctoides) were given preference tests in which they could approach an empty chamber, a mirror, a familiar conspecific, or an unfamiliar conspecific. Control subjects tended to withdraw from the mirror, and threatened the stranger more than did monkeys whose early social experience had occurred exclusively in darkness. Both groups explored the familiar stimulus animal most of all, but the group socialized in the dark showed most positive behavior when in the empty chamber. In a second study peer-reared infants responded more appropriately to slides of conspecifics than did infants reared with a mirror as the main source of social input. Infants reared only with a peer were also strongly attracted to a mirror, whereas infants reared only with mirrors preferred a film of an unfamiliar agemate. The results suggest that early visual social stimulation is important in the development of aggression and other social behaviors, and that novelty and complexity are important aspects of social stimuli that interact with effects of early experience. Study 2 was conducted while the first author was in receipt of a Postgraduate Research Studentship from the U.K. Science Research Council. The DTU tapes were analyzed using a computer program developed with the help of SRC grant B/RG 98910 to A. Chamove. This latter grant also supported the study from which the preference test data were taken.