Drug effects in squirrel monkeys trained on a multiple schedule with a punishment contingency

The behavior of four monkeys trained on a multiple schedule was differentially sensitive to selected pharmacological agents. The three components of the multiple schedule were: (1) a variable-interval schedule in which responses were reinforced on the average of once per minute; (2) a concurrent schedule in which every tenth response was reinforced and every fifteenth response, on the average, was shocked; and, (3) a neutral stimulus in the presence of which responses were neither reinforced nor shocked. Pentobarbital, chlordiazepoxide, and meprobamate increased responding during each of the components. Scopolamine and d-amphetamine decreased variable-interval performance, had minimal effects on performance during the concurrent-schedule component, and increased responding in the presence of the neutral stimulus. Chlorpromazine decreased variable-interval responding and had slight effects on the responding during the other two components.     

Some effects of punishment shock intensity upon discriminative responding

Three pigeons received visual discrimination training under both multiple variable-ratio extinction and variable-interval extinction schedules. All birds developed nearly perfect discrimination. When punishment for every tenth response during food reinforcement was presented, responding decreased as shock intensity increased. At the same time, responding during extinction, which was not punished, increased at intermediate punishment intensities, but returned to low levels under severe punishment. A second procedure, in which punishment and no-punishment sessions alternated unsystematically, was employed with two of the birds. The results under this procedure essentially replicated the data obtained as punishment shock intensity increased gradually.     

Effects of shock intensity and duration on the frequency of biting attack by squirrel monkeys

Squirrel monkeys were periodically exposed to brief tail-shocks in the presence of a rubber tube connected to a pneumatic switch. Biting attack upon this tube was found to be a decreasing function of time since shock delivery and a direct function of shock intensity and duration. These results parallel findings in investigations employing more “naturalistic” social situations, indicating that attack against the inanimate and animate environment is a direct function of the intensity of an aversive stimulus. The results also demonstrate that frequency of biting attack as a datum is sensitive to several experimental manipulations.     

Tolerance to and residual effects of cocaine in squirrel monkeys depend on reinforcement-schedule parameter.

Lever pressing by 4 squirrel monkeys was maintained under a three-component multiple fixed-ratio schedule of food presentation; components differed with respect to ratio size. For each monkey, acute administration of cocaine (0.03 to 1.3 mg/kg, i.m.) produced dose-dependent decreases in overall response rate in each component. During repeated daily administration of 1.0 mg/kg of cocaine, tolerance developed to the rate-decreasing effects under each of the ratio contingencies, but developed to a greater extent and was evident in earlier parts of sessions for performance under the smaller ratios. Response rates of 2 monkeys increased above nondrug control levels despite the putative reinforcer not being consumed during the session. When saline or a smaller dose of cocaine was substituted for 1.0 mg/kg, response rates often were suppressed below nondrug control-level responding. This suppressive effect was observed in each monkey and was more likely to be observed and/or to be of greater magnitude in large-ratio components for 3 of the 4 monkeys. When saline was administered chronically at the end of the chronic-drug phase, response rates remained suppressed in the large-ratio component for 2 of the monkeys. There was, therefore, a schedule-dependent dissociation between behavioral tolerance and the residual effects: Tolerance was greater when small ratios were arranged, whereas the residual effects were more pronounced when larger ratios were arranged.     

Measurement of social dominance in squirrel monkeys

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

A measure of intensity of parental punishment

To test the possibilities that antecedents and consequents of certain levels of intensity of punishment may have far-reaching effects on behavior, a self-report measure of parental intensity of punishment was developed. Consisting of 33 different situations to which parents react, scores from the instrument were found to be reliable over time. Further construct validity was demonstrated with a variety of predicted relationships between punishment intensity and parent and child characteristics. Five samples of subjects were used with over 400 families, high intensity of punishment scores were found to be related to mothers' lack of warmth and to her intrusiveness when playing with her child; children's maladjusted behavior; aggression and impulsivity in boys; withdrawal and inhibition in girls, and uncooperativeness. Inconsistency of parental punishment also was associated with maladjustment. Results were discussed in terms of Rotter's social learning theory.     

The Thatcher illusion in squirrel monkeys (Saimiri sciureus)

Like humans, Old World monkeys are known to use configural face processing to distinguish among individuals. The ability to recognize an individual through the perception of subtle differences in the configuration of facial features plays an important role in social cognition. To test this ability in New World monkeys, this study examined whether squirrel monkeys experience the Thatcher illusion, a measure of face processing ability in which changes in facial features are difficult to detect in an inverted face. In the experiment, the monkeys were required to distinguish between a target face and each of the three kinds of distracter faces whose features were altered to be different from those of the target. For each of the pairs of target and distracter faces, four rotation-based combinations of upright and inverted face presentations were used. The results revealed that when both faces were inverted and the eyes of the distracter face were altered by rotating them at an angle of 180° from those of the target face, the monkeys' discrimination learning was obstructed to a greater extent than it was under the other conditions. Thus, these results suggest that the squirrel monkey does experience the Thatcher illusion. Furthermore, it seems reasonable to assume that squirrel monkeys can utilize information about facial configurations in individual recognition and that this facial configuration information could be useful in their social communications.     

The effect of punishment shock intensity upon responding under multiple schedules

In the first of two experiments, responses of two pigeons were maintained by multiple variable-interval, variable-ratio schedules of food reinforcement. Concurrent punishment was introduced, which consisted of a brief electric shock after each tenth response. The initial punishment intensities had no lasting effect upon responding. Then, as shock intensity increased, variable-ratio response rates were suppressed more quickly than variable-interval response rates. When shock intensity decreased, variable-interval responding recovered more quickly, but the rates under both schedules eventually returned to their pre-punishment levels. In the second experiment, the following conditions were studied in three additional pigeons: (1) With each shock intensity in effect for a number of sessions, punishment shock intensity was gradually increased and decreased and responding was maintained by multiple variable-ratio, fixed-ratio schedules of food reinforcement; (2) Changes in punishment shock intensity as described above with responding maintained by either a variable-ratio or a fixed-ratio schedule, which were presented on alternate days; (3) Session-to-session changes in shock intensity with responding maintained by multiple variable-ratio, fixed-ratio schedules. Responding under the two schedules was suppressed to approximately the same extent by a particular shock intensity. Also, post-reinforcement pauses under the fixed-ratio schedule increased as response suppression increased.     

Determinants of serial discrimination learning by squirrel monkeys

Squirrel monkeys were presented multiple serial discriminations 1, 2, 4, and 8 problems long. They were then presented problems designed to separate the effects of within-list associative interference from the effects of within-problem intertrial interval as list length was increased. The Ss committed consistently fewer errors after Trial 1 reward than after Trial 1 nonreward and showed strong stimulus perseveration. An increase in within-problem intertrial interval from 30 sec to 4 min had no effect whereas the associative interference resulting from increased problem length caused a small but significant performance decrement. Old and new problems had about equal effects on serial discrimination. The findings indicated that squirrel monkeys are relatively insensitive to within-problem associative interference.     

Resistance to punishment as a function of intensity and frequency of prior punishment experience

Rats with a history of intermittent punishment have been found to persist in the face of continuous punishment. It was predicted from an extension of frustration theory to punishment that increasing the intensity or frequency of intermittent punishment would increase persistence to high fear elicited by continuous punishment. Two experiments, employing 310 rats, verified this prediction for both intensity and frequency manipulations but indicated rather narrow boundary conditions for their effects.     

Some effects of punishment on pain-elicited aggression

Painful mechanical tail-pinch elicited aggressive responses in paired rats; response-contingent electric shock to either forepaws or hindpaws suppressed fighting and stereotyped aggressive postures, including those in which dominance was expressed. There was no evidence that aggression was facilitated by shock that was contingent on pain-elicited aggressive responses. Aggressive responding recovered when shock was discontinued.     

Selective punishment of interresponse times: The roles of shock intensity and scheduling

Two experiments investigated the roles of shock intensity and scheduling in selective punishment of interresponse times. In each experiment the punishment contingencies were imposed on a background of rats' responding maintained by a variable-interval schedule of food presentation. In Experiment 1 all interresponse times greater than 8 seconds produced shock. In Experiment 2 all interresponse times greater than 8 seconds but less than 12 seconds produced shock. In each experiment shock intensity was initially 0.3 milliamperes (mA) and then was varied through an ascending sequence ranging from 0.1 mA to 0.4 mA, in 0.1-mA increments. Experiment 1 produced response-rate increases at low intensities (0.1 and 0.2 mA) but eliminated responding at the remaining intensities. Experiment 2 produced response-rate increases only with 0.1-mA shock, although responding was maintained at all shock parameters investigated. Analysis of the interresponse times per opportunity showed differential suppression of the targeted responses in all cases except the high-intensity shock phases of Experiment 1. The current data support and extend previous studies of selective interresponse-time-dependent shock schedules but suggest that response-rate increases are not a necessary outcome of this type of procedure. The view that variable-interval schedules of shock presentation selectively target long interresponse times was also supported.