Schedule-induced drinking as a function of interreinforcement interval in the rhesus monkey

Lever presses by two rhesus monkeys produced food pellets that were assigned by both an ascending and descending series of fixed-interval schedules whose values varied between 1 and 512 sec. The amount of schedule-induced drinking was bitonically related to interreinforcement interval, reaching a maximum at approximately 120 sec and declining at longer fixed intervals. The relation between water intake and interreinforcement interval was complexly related to two drinking measures: (1) the probability of drinking following a pellet and (2) the amount drunk per bout. Drinking rate was also bitonically related to interreinforcement interval.     

Effects on responding of mixed and multiple schedules of signalled and unsignalled response-dependent electric-shock delivery

Responding in two rats was maintained under mixed and multiple variable-interval 35-sec variable-interval 35-sec food delivery schedules. Similar rates and patterns of responding occurred in each component of the two schedules. Mixed and multiple variable-interval 65-sec variable-interval 65-sec schedules of response-dependent shock delivery were super-imposed on the mixed and multiple baseline food schedules, respectively. In one component, a 5-sec stimulus was presented on the average of once every 65 sec. Offset of the stimulus arranged that the next response would produce shock. In the other component, no stimulus was presented during the 5-sec period. The mixed schedule of signalled and unsignalled dependent shock delivery yielded similar degrees of response suppression in each component, but the multiple schedule of shock delivery revealed differential degrees of response suppression. Considerably more suppression occurred in the component not associated with the preshock stimulus, thus implicating the discriminative functions of the correlated stimulus.     

An inverse relationship between baseline fixed-interval response rate and the effects of a tandem response requirement.

Previous experiments examining the effects of adding a tandem fixed-ratio response requirement on fixed-interval schedule performance have reported inconsistent results. One variable that may account for such inconsistencies is the baseline response rate in the fixed-interval condition. This possibility was investigated in the present study. Rats were given histories with either interresponse times greater than 11 s or fixed-ratio 40 schedules of reinforcement, which engendered either relatively low or high rates of responding, respectively, in the subsequent fixed-interval condition. A tandem ratio response requirement (fixed-ratio 9) was then introduced. The effects of adding this tandem response requirement were inversely related to the baseline fixed-interval response rates; low rates of responding in the fixed-interval condition were markedly increased, whereas high rates of responding were relatively unaffected. This inverse relationship appears to be similar to the rate-dependent relations observed in behavioral pharmacology. These results may provide an explanation for the inconsistent findings reported in previous studies on tandem fixed-interval fixed-ratio schedules and suggest that principles of behavioral pharmacology research may be applicable to the study of the effects of nonpharmacological variables on schedule-controlled behavior.     

Determinants of pausing under variable-ratio schedules: Reinforcer magnitude, ratio size, and schedule configuration

Pigeons pecked a key under two-component multiple variable-ratio schedules that offered 8-s or 2-s access to grain. Phase 1 assessed the effects of differences in reinforcer magnitude on postreinforcement pausing, as a function of ratio size. In Phase 2, postreinforcement pausing and the first five interresponse times in each ratio were measured as a function of differences in reinforcer magnitude under equal variable-ratio schedules consisting of different configurations of individual ratios. Rates were also calculated exclusive of postreinforcement pause times in both phases. The results from Phase 1 showed that as ratio size increased, the differences in pausing educed by unequal reinforcer magnitudes also increased. The results of Phase 2 showed that the effects of reinforcer magnitude on pausing and IRT durations were a function of schedule configuration. Under one configuration, in which the smallest ratio was a fixed-ratio 1, pauses were unaffected by magnitude but the first five interresponse times were affected. Under the other configuration, in which the smallest ratio was a fixed-ratio 7, pauses were affected by reinforcer magnitude but the first five interresponse times were not. The effect of each configuration seemed to be determined by the value of the smallest individual ratio. Rates calculated exclusive of postreinforcement pause times were, in general, directly related to reinforcer magnitude, and the relation was shown to be a function of schedule configuration.     

Within-session meal-size effects on induced drinking.

As a control for the effects of session duration and hunger on the relation between food magnitude and induced drinking, four food-deprived rats were exposed to a variable-time 50-s schedule of food delivery in which the size of each food delivery varied randomly within sessions. Food-related behavior and schedule-induced drinking per opportunity were examined as functions of meal size and postfood time. All rats showed an inverted-U-shaped relation between drinking per opportunity and meal size. This relation was caused by variation in the percentage of intervals that contained drinking and by variation in the number of drinking bouts per interval, rather than by bout duration or by the amount of drinking within those intervals that actually contained drinking. Head-in-feeder time increased linearly with meal size. Schedule-induced drinking was entrained by food delivery in 3 of 4 subjects; the entrainment was due to regulation of the starting time of each drinking bout rather than to regulation of bout duration.     

Interpersonal contingencies: Performance differences and cost-effectiveness

Three reinforcement contingencies were compared with regard to performance differences and cost-effectiveness (i.e., responses per unit reinforcer). Pairs of college students were studied under individual, cooperative, or competitive contingencies using a concurrent setting that included one of these three contingencies as one alternative and a lower paying individual contingency as the other alternative. With the individual and the cooperative contingencies, overall response rates were typically high; under competitive contingencies the overall response rates were substantially lower. Subjects responded at very high rates when competing, but chose not to compete most of the time. Competition and cooperation produced the most cost-effective responding, assessed as the number of responses made per $.01 of reinforcer. High overall rates of competitive responding were obtained when the contests were longer and the lower paying alternative contingency was not available.     

Choice behavior of rats in a concurrent-chains schedule: Amount and delay of reinforcement

Rats were exposed to concurrent-chains schedules in which the terminal links were equal fixed-interval schedules terminating in one or three food pellets. Choice proportions for large reward increased with increases in delay intervals programmed on fixed-interval schedules and supported the predictions derived from a general choice model originally formulated by Fantino and later developed by Navarick and Fantino. In addition, a functional equivalence of two alternatives was established by increasing delay intervals with large reward, whereas delay intervals for small reward were held constant. Functionally equivalent delay intervals with large reward, for each delay interval with small reward, can be described by a power function with exponent smaller than 1.0. A better prediction of choice proportions resulted when this function was used to derive predicted choice proportions.     

Instructed versus shaped human verbal behavior: Interactions with nonverbal responding

Undergraduate students' presses on left and right buttons occasionally made available points exchangeable for money. Blue lights over the buttons were correlated with multiple random-ratio random-interval components; usually, the random-ratio schedule was assigned to the left button and the random-interval to the right. During interruptions on the multiple schedule, students filled out sentence-completion guess sheets (e.g., The way to earn points with the left button is to...). For different groups, guesses were shaped with differential points also worth money (e.g., successive approximations to “press fast” for the left button), or were instructed (e.g., Write “press slowly” for the left button), or were simply collected. Control of rate of pressing by guesses was examined in individual cases by reversing shaped or instructed guesses, by instructing pressing rates, and/or by reversing multiple-schedule contingencies. Shaped guesses produced guess-consistent pressing even when guessed rates opposed those characteristic of the contingencies (e.g., slow random-ratio and fast random-interval rates), whereas guesses and rates of pressing rarely corresponded after unsuccessful shaping of guesses or when guessing had no differential consequences. Instructed guesses and pressing were inconsistently related. In other words, when verbal responses were shaped (contingency-governed), they controlled nonverbal responding. When they were instructed (rule-governed), their control of nonverbal responding was inconsistent: the verbal behavior sometimes controlled, sometimes was controlled by, and sometimes was independent of the nonverbal behavior.     

The effects of a salient self-schema on the evaluation of proattitudinal editorials: Top-down versus bottom-up message processing

The effects of a salient self-schema on message evaluation were studied. Subjects were identified who characterized themselves using trait adjectives that reflected the prototype of either a “religious” or a “legalistic” person. Equally persuasive sets of proattitudinal messages were developed empirically using weak arguments. Half of the messages were developed to reflect a “religious” perspective on the issue (capital punishment, abortion) whereas half were developed to reflect a “legalistic” perspective on the issue. Religious and legalistic subjects were then exposed to religious or legalistic arguments supporting an equally acceptable position (e.g., eliminating capital punishment). Afterward, subjects evaluated the persuasiveness of the communication and listed their thoughts as part of a “curriculum development project.” Results suggested that subjects when exposed to a schema-relevant message arguments for a position in which they believed were more positive about the quality of the message arguments and in their cognitive responding. These data extend the heuristic value of selfschemata to the area of attitudes and suggest that cognitive responses in persuasion are subjectively rather than objectively rational.     

Attribution and reconstructive memory

Two experiments were conducted to test the effects of making an attribution on later memory for the event that gave rise to the attribution. Subjects in Experiment 1 observed a scenario in which an actor's behavior was associated with high or low variance (distinctiveness) across situations, and high or low congruence (consensus) to the actions of others. Subjects either made attributions for the actor's behavior immediately following the scenario or not. One week later, subjects were asked to recall consensus and distinctiveness for the actor's original behavior. Subjects who made attributions were significantly better at estimating the high-high and low-low combinations of consensus and distinctiveness than were their no-attribution counterparts. It was suggested that making an attribution may allow for a reconstructed memory for the original event, but not enhance direct access to the original event information. A second experiment tested this concept further by having subjects view an edited version of the scenario in which either the distinctiveness or the consensus information was deleted and having subjects make attributions or not. One week later, subjects were asked to indicate their certainty that consensus and distinctiveness information was a part of the original scenario and to estimate the levels of consensus and distinctiveness. Subjects who made attributions were more confident and accurate in estimating the level of consensus or distinctiveness that was given in the original scenario than were no-attribution subjects. However, attribution subjects were also more confident that consensus information or distinctiveness information was contained in the scenario (when it was not) than were the noattributio subjects. Results of the two experiments suggest that eliciting attributions can distort subsequent memory for the event on which the attributions were based.