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We investigated the effects of differential and nondifferential reinforcers on divided control by compound‐stimulus dimensions. Six pigeons responded in a delayed matching‐to‐sample procedure in which a blue or yellow sample stimulus flashed on/off at a fast or slow rate, and subjects reported its color or alternation frequency. The dimension to report was unsignaled (Phase 1) or signaled (Phase 2). Correct responses were reinforced with a probability of.70, and the probability of reinforcers for errors varied across conditions. Comparison choice depended on reinforcer ratios for correct and incorrect responding; as the frequency of error reinforcers according to a dimension increased, control (measured by log d) by that dimension decreased and control by the other dimension increased. Davison and Nevin's (1999) model described data when the dimension to report was unsignaled, whereas model fits were poorer when it was signaled, perhaps due to carryover between conditions. We are the first to test this quantitative model of divided control with reinforcers for errors and when the dimension to report is signaled; hence, further research is needed to establish the model's generality. We question whether divided stimulus control is dimensional and suggest it may instead reflect joint control by compound stimuli and reinforcer ratios. [ABSTRACT FROM AUTHOR]

Organisms may sometimes behave as if a contingency exists between behavior and consequences, even if this is not actually the case. Killeen (1978) suggested that such superstition occurs because of factors that bias subjects to behave "superstitiously" rather than because of failures of discrimination. We systematically replicated Killeen's experiment and compared contingency discrimination between different consequences. Six pigeons responded in a matching‐to‐sample procedure in which a response‐independent or response‐dependent stimulus change, food delivery, or blackout occurred. The pigeons reported whether the consequence was response dependent or response independent by choosing between two side keys. Discrimination was strongest after stimulus changes, weaker after blackouts, and weakest after food deliveries. These differences persisted even after additional training, suggesting asymmetries that may reflect differences in the disruptive effects of different consequences on remembering and/or behavioral mnemonics. Importantly, the pigeons were not biased to report response‐dependent consequences unless that response was consistent with locational biases; that is, they behaved "superstitiously" when there was a reason to be biased to do so. These findings corroborate Killeen's and demonstrate that behavior may deviate from contingencies not necessarily because subjects cannot discriminate those contingencies but because they are biased to behave otherwise. [ABSTRACT FROM AUTHOR]

Highlights • Control by stimuli signaling future reinforcer availability is often weaker in more certain environments. • We examined whether this was the case when reinforcer availability changed over time. • Across conditions, we varied the certainty of the next-reinforcer location at a particular time. • Stimuli strongly controlled behavior and environmental contingencies exerted weak control. • Control by stimuli and by the environment may depend on global, not local, environmental certainty. Abstract Several studies suggest that the degree of control by reinforcer ratios (environment tracking) and by exteroceptive stimuli that signal future reinforcer availability (signal following) depends on environmental certainty: As reinforcers become more likely at one location, environmental contingencies exert stronger control and exteroceptive stimuli exert weaker control. This research has not yet been extended to environments in which reinforcer availability changes across time, even though such changes are present in most natural environments. Thus, in the present experiment, we examined environment tracking and signal following in a concurrent schedule in which the reinforcer ratio reversed to its reciprocal 30 s after a reinforcer delivery and keylight-color stimuli signaled the likely or definite time or location of the next reinforcer. Across conditions, we manipulated environmental certainty by varying the probability of reinforcer deliveries on the locally richer key. This made the location of future reinforcers at a particular time more or less certain, but did not change the overall reinforcer ratio. Changes in local environmental certainty had little to no effect on environment tracking and signal following; in all conditions, keylight-color stimuli strongly controlled choice and reinforcer ratios exerted weak control. The present findings suggest that the extent of environment tracking and signal following is primarily determined by global, not local, environmental certainty. [ABSTRACT FROM AUTHOR]

• Stimuli signaling reinforcement reduce responding on one alternative of a concurrent schedule. • We asked how signal reliability affects choice between signaled and unsignaled alternatives. • Signal reliability changed responding on the signaled alternative, but not the unsignaled alternative. • These results are consistent with matching theories, but not with research showing changes in responding on both alternatives. • Response competition and local reinforcer rates may modulate effects of signaled reinforcement in concurrent schedules. When reinforcer availability on one alternative of a concurrent schedule is signaled by a discriminative stimulus, responding on that alternative decreases. We investigated how the correlation between signal presentation and reinforcement (signal reliability) affects choice between signaled and unsignaled alternatives. Six pigeons responded in a concurrent schedule, in which reinforcers on one alternative were signaled by a key-color change. Across conditions, the probability of reinforcement following signal presentation varied (the probability in its absence was the complement). As signal reliability increased, response rates and latencies following signal onset on the signaled alternative decreased, whereas responding on the unsignaled alternative remained unchanged. Because the signal did not alter overall reinforcer rates, these findings are consistent with matching theories and research suggesting that responding on one alternative of a concurrent schedule depends on reinforcer, but not response, rates on other alternatives. However, these findings are inconsistent with others demonstrating concomitant changes in responding on signaled and unsignaled alternatives. We consider whether a response-competition account of concurrent performance can explain these discrepancies, and suggest avenues for future studies to investigate the mechanisms underlying effects of signaled reinforcement in concurrent schedules. [ABSTRACT FROM AUTHOR]