Reciprocal cooperation in dyads

This study investigated the conditions that promote long-term social exchange when the immediate payoff for social participation is equal to or less than for individual responding. The 10 subjects, from a special education unit and ranging between 10 and 16 years of age, comprised five dyads to participate in daily 20-min sessions. During the first experiment, the subjects sat beside each other and in front of an automated apparatus which automatically distributed points (representing money) to self, to partner, or to the group. During baseline conditions, the subjects could earn reinforcers from all three modes. During the dependency conditions, which alternated between subjects at 3-day intervals, one subject could earn reinforcers from all three modes while a partner could earn reinforcers only from the mode requiring subject's assistance. Four of the five dyads increased their levels of cooperative responding during the several reversals in which first one and then the other subject was dependent upon the partner for reinforcement. This pattern maintained when the method of distributing reinforcers was changed to a manual procedure requiring the experimenter to record point distributions by transferring beads on an abacus. This suggested that the distribution modes rather than the experimental apparatus were important in promoting the cooperative pattern. In the second experiment all subjects continued to cooperate with partner, even when they could have earned more by working alone. Eventually a value for the self mode was reached where the subjects discontinued their cooperation to work for self.     

On being imitated: Effects on models and observers

Forty first- and second-grade children were imitated by an adult confederate and not imitated by a second adult confederate. For each child exposed to the above treatment, another child observed the imitation and nonimitation. It was found that children tended to be attracted to the confederate who imitated them. More importantly, although the observers were not imitated, they also were attracted to the imitating confederate. The two groups did not differ significantly in subsequent imitation of the two confederates. The results, which were conceptualized within the framework of vicarious reinforcement, have methodological implications for research on the effects of being imitated.     

Psychophysics of key-peck duration in the pigeon

The duration of the pigeon's key peck was differentially reinforced in either a trials or a free-operant procedure. Mean emitted peck duration was a power function of the duration required for food delivery to occur. The exponents of the power function differed considerably from those observed in earlier research involving longer duration responses in pigeons and other species. The coefficients of variation also did not correspond with those of the earlier research on other responses, nor did consideration of the durations actually reinforced resolve the differences. Duration was neither a function of response rate nor of intermittency of reinforcement. Key-peck duration was changed in an orderly way by differential reinforcement. However, it appeared to be more strongly determined by its duration in the absence of differential reinforcement than were longer duration responses.     

Discriminative functions of schedule stimuli and memory: a combination of schedule and choice procedures

Pigeons responded under a combination brief-stimulus schedule and choice procedure. Normally, a fixed-interval schedule was in effect, where completion randomly produced either a brief stimulus or food. Intermittently, this schedule was interrupted by a choice arrangement. Two choice keys were lit, either a short or a long time since a prior event (food or stimulus). One choice response produced food if the time had been short, and the alternate response produced food if the time had been long. Across conditions, the duration of the fixed-interval schedule was varied, the stimuli that comprised the brief-stimulus operation were changed, and the stimuli were presented as paired and nonpaired with food. The focus of the study was the control of both schedule performance and choice responding across conditions. The results showed that choice accuracy was correlated with the degree of fixed-interval curvature, the response pattern of a pause followed by a gradually accelerated rate. As fixed-interval schedule duration was increased, both the degree of fixed-interval curvature and choice accuracy decreased. The particular brief stimulus used affected schedule and choice performance, with a more salient stimulus producing a greater degree of curvature and higher accuracy. Pairing and nonpairing operations produced striking differences in performance with the less salient brief stimulus, but not with the more salient stimulus. The results suggest that brief-stimulus schedule performance may be conceptualized in the context of memory research.     

Effect of punishment on human variable-interval performance

Three female human subjects pressed a button for monetary reinforcement in a range of variable-interval schedules specifying different frequencies of reinforcement. On alternate days, responding was also punished (by subtracting money) according to a variable-ratio 34 schedule. In the absence of punishment, rate of responding was an increasing negatively accelerated function of reinforcement frequency; the relationship between response rate and reinforcement frequency conformed to Herrnstein's equation. The effect of the punishment schedule was to suppress responding at all frequencies of reinforcement. This was reflected in a change in the values of both constants in Herrnstein's equation: the value of the theoretical maximum response-rate parameter was reduced, while the parameter describing the reinforcement frequency corresponding to the half-maximal response rate was increased.     

Reinforcement by an imprinting stimulus versus water on simple schedules in ducklings

Ducklings (5 to 28 days old) were trained to peck a pole on fixed-ratio, fixed-interval, and multiple schedules using brief presentation of an imprinting stimulus as the response-contingent event. Other ducklings of the same age were trained similarly except that reinforcement consisted of access to water. With water reinforcement the typical fixed-ratio (“break-run”), fixed-interval (“scallop”), and multiple schedule response patterns were readily established and consistently maintained. With the imprinting stimulus these schedule effects were inconsistent in some subjects and virtually nonexistent in others, despite extended training. Schedule control with the imprinting stimulus was not improved by the use of a reinforcement signaling procedure which enhances responding reinforced by electrical brain stimulation on intermittent schedules. However, the overall rates of responding and the extinction functions generated after reinforcement with water versus the imprinting stimulus were comparable. These findings imply that control by temporal and discriminative stimuli may be relatively weak when a young organism's behavior is reinforced by presentation of an imprinting stimulus.