Observational learning of two visual discriminations by pigeons: a within-subjects design.

Pigeon's observational learning of successive visual discrimination was studied using within-subject comparisons of data from three experimental conditions. Two pairs of discriminative stimuli were used; each bird was exposed to two of the three experimental conditions, with different pairs of stimuli used in a given bird's two conditions. In one condition, observers were exposed to visual discriminative stimuli only. In a second condition, subjects were exposed to a randomly alternating sequence of two stimuli where the one that would subsequently be used as S+ was paired with the operation of the grain magazine. In a third experimental condition, subjects were exposed to the performance of a conspecific in the operant discrimination procedure. After exposures to conspecific performances, there was facilitation of discriminative learning, relative to that which followed exposures to stimulus and reinforcement sequences or exposures to stimulus sequences alone. Exposure to stimulus and food-delivery sequences enhanced performance relative to exposure to stimulus sequences alone. The differential effects of these three types of exposure were not attributable to order effects or to task difficulty; rather, they clearly were due to the type of exposure.     

The effect of negative stimulus presentations on observing-response rates

Theories of observing differ in predicting whether or not a signal for absence of reinforcement (S−) is capable of reinforcing observing responses. Experiments in which S− was first removed from and then restored to the procedure have yielded mixed results. The present experiments suggest that failure to control for the direct effect of presenting S− may have been responsible. Pigeons and operant procedures were used. Experiment 1 showed that presentations of S−, even when not contingent on observing, can raise the rate of an observing response that was reinforced only by presentations of a signal (S+) that accompanied a schedule of food delivery. Experiment 2 showed that this effect resulted from bursts of responding that followed offsets of S−. Experiment 3 showed that, when the presence of S− was held constant, lower rates occurred when S− was dependent on, rather than independent of, observing. These results support theories that characterize S− as incapable of reinforcing observing responses.     

Preference for less segmented fixed-time components in concurrent-chain schedules of reinforcement

A concurrent-chain procedure was used to examine choice between segmented and less segmented response-independent schedules of reinforcement. A pair of independent, concurrent variable-interval 60-s schedules were presented in the initial link, along with a 1.5-s changeover delay. A chained fixed-interval fixed-time and its corresponding tandem schedule constituted the terminal links. The length of the fixed-interval schedule in the terminal link was varied between 5 s and 30 s while that of the fixed-time schedule was kept at 5 s over conditions. The first components of both terminal-link schedules were accompanied by the same stimulus. Except in the baseline condition, the onset of the second component of the terminal-link chained schedule was accompanied by either a localized (key color) or a nonlocalized (dark houselight) stimulus change. Stimulus conditions were constant during the terminal-link tandem schedule. With three exceptions, pigeons demonstrated a slight preference for the tandem over the chained schedule in the terminal link. Furthermore, this preference varied inversely with the length of the first component. In general, these results are consistent with previous studies that reported an adverse effect on choice by segmenting an interval schedule into two or more components, but they are inconsistent with studies that reported preference for signaled over unsignaled delay of reinforcement.     

Temporal control by signals of interval duration within variable-interval schedules

Rats' lever pressing produced sucrose reinforcers on a variable-interval schedule where, in different conditions, the duration of a stimulus presented immediately after reinforcement was either correlated or uncorrelated with the duration of the current interreinforcement interval. Under the baseline schedule, in which no stimulus was presented, the minimum interreinforcement interval was 8 s and the mean postreinforcement pause of each subject approximated this value. Response rates increased slowly over the first 10 to 15 s and then remained roughly constant throughout the remainder of the interval. In both the correlated and uncorrelated conditions, the added stimulus resulted in the postreinforcement pauses lengthening to values in excess of the duration of the preceding stimulus. This resulted in a poststimulus pause which was, in most cases, roughly constant irrespective of the duration of the preceding stimulus, or of the reinforcement contingencies prevailing immediately after stimulus offset. Local response-rate patterns in the uncorrelated conditions were similar to those obtained under the baseline schedule in which no stimulus was presented. However, in the correlated condition local response rates increased across the remainder of the interreinforcer interval. Further, the rate of acceleration was inversely related to the duration of the preceding stimulus. These results show that a correlation between stimulus duration and the ensuing time to reinforcement can control behavior—a type of temporal control not previously reported.     

A review on equivalence-based procedures to teach food-portion estimation skills

This review involved a systematic analysis of equivalence-based instruction (EBI) that aimed to improve food-size interventions in diverse populations. Systematic searches identified seven studies published since 2010 that met inclusion criteria. These studies were analyzed according to their participants, design, setting, content taught, training structures, training protocol, testing format, treatment integrity, and outcomes. Results showed EBI procedures for teaching food estimation skills have been mostly implemented with adults. The type of content taught in the identified studies included carbohydrate ranges, portion size with food and non-food items, measuring cups and nutritional content of calories. Majority of included studies used one-to-many training structure and simultaneous protocols for teaching stimulus relations. Five studies completed a generalization probe and three studies reported treatment integrity data. Overall, all participants demonstrated skill acquisition of novel relations between food and portion measurement aides. Recommendations for future research and clinical applications of EBI in teaching food portion estimation are presented.     

Evaluating public posting,goal setting,and rewards to increase physical activity in children

In this study, we evaluated several components of a pedometer-based intervention with children in an elementary-school-aged classroom, across 24-h sessions. The intervention included combinations of self-monitoring, goal setting, feedback, and reinforcement, and data were analyzed at both the classroom level (i.e., average daily step totals) and the individual level (i.e., daily step totals), across phases. The highest levels of physical activity were observed when components of self-monitoring, public posting, goal setting, and feedback with reward were applied concurrently.     

Fragile promise: The role of justification in promise-breaking

People who consider themselves moral sometimes use self-serving justifications to rationalize their selfish behaviours. Previous studies have tested the role of ambiguity in justifying wrongdoings, but it remains unclear whether ambiguity also plays a role in justifying promise-breaking behaviour and whether heterogeneity exists. To investigate justification in promise-breaking, we introduced a new experimental paradigm called the card-guessing task and used hierarchical cluster analysis to classify participants based on their promise-breaking decisions in unambiguous and ambiguous conditions. Experiment 1 revealed three clusters of solutions: Cluster 1 always kept their promises (i.e., keepers); Cluster 2 only exploited the vague promises and broke their promises in the ambiguous condition (i.e., intermediates); Cluster 3 tended to take advantage of vague promises and broke their promises irrespective of ambiguity (i.e., breakers). Experiment 2 confirmed that participants in the three clusters differed in their norm-abiding preferences and social value orientations. Keepers were more altruistic and had a stronger sense of norm compliance than intermediates and breakers. In conclusion, our study demonstrates that self-serving justifications were more likely to be employed by people who are moderately sensitive to deviation from social norms, which has implications for strategic interventions and policy formulation concerning unethical behaviour.