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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]

Highlights • We studied stimulus generalization of response patterns in a multiple peak procedure. • Two training stimuli differentially signaled an FI 5-s and FI 20-s schedule. • Response-rate patterns to one training stimulus generalized nearly exclusively. • This research provides a strong starting point for future studies of generalization under FI schedules. • A thorough understanding of generalization under FI schedules requires analyzing a range of dependent variables. Abstract Stimulus generalization is typically assessed by analyzing overall response rates. Studies of generalization of response-rate patterns across time are less common, despite the ubiquitous nature of time and the strong temporal control over behavior in the natural world. Thus, we investigated generalization of response-rate patterns across time using a multiple peak procedure in pigeons. The frequency (fast or slow) at which the color of a keylight changed signaled a fixed-interval (FI) 5-s or 20-s schedule, counterbalanced across subjects. In peak trials, the frequency of keylight-color changes was varied. For the fast and slow training stimuli, response rates in peak trials were controlled by the arranged FI schedule value; they increased as the arranged reinforcer time approached, and decreased thereafter. Response-rate patterns to all test stimuli were similar to response-rate patterns to the slow training stimulus for all subjects. Thus, overall, strong generalization from the slow training stimulus to all test stimuli was evident, whereas there was little to no generalization from the fast training stimulus. These findings extend past research examining generalization of temporally controlled response-rate patterns, and provide a useful starting point for future investigations of generalization of fixed-interval responding. A thorough understanding of generalization processes requires analysis of dependent variables other than overall response rates, especially when responding is likely to be temporally controlled. [ABSTRACT FROM AUTHOR]

In concurrent schedules with a changeover delay (COD), choice often strongly favours the just-reinforced alternative immediately after a reinforcer delivery. These ‘preference pulses’ may be caused by a change in reinforcer availability created by the COD, and/or because the COD decreases the overall probability of switching. We investigated which explanation better accounts for preference pulses by arranging concurrent schedules that allowed us to separate the COD’s effects on reinforcer availability from its effects on the probability of switching. When the reinforcer ratio was 1:1, pulses were inconsistently accompanied by changes in reinforcer availability, but consistently accompanied by longer visits. These pulses appeared to be related only to the decreased probability of switching caused by the COD, providing the first evidence of pulses after reinforcers caused by the probability of switching alone. When the reinforcer ratio was 1:5 or 5:1; preference pulses were accompanied by changes in reinforcer availability and by longer visits. These pulses appeared to be related to the COD’s effects on reinforcer availability, although a small portion appeared to be related to low probability of switching. These findings suggest that the COD affects preference pulses by both decreasing the probability of switching and creating a change in reinforcer availability. [ABSTRACT FROM AUTHOR]

When short-term memory is assessed in the delayed matching-to-sample (DMTS) procedure, performance is better when cues signal larger reinforcer magnitudes or higher reinforcer probabilities for correct responding. Previous studies demonstrating signaled-magnitude or signaled-probability effects presented cues for a prolonged period during the sample stimulus and/or retention interval. The present study asked whether a signaled-probability effect would occur with brief post-sample cues that signaled the presence or absence of reinforcement. Five pigeons responded in a DMTS task in which sample stimuli were sometimes followed by a 0.5-s cue signaling that reinforcers would either be available or not available in the current trial, and the retention interval varied from 0.5 s to 20 s. A reliable signaled-probability effect was found when reinforcers were arranged independently and for all correct responses, whereas a smaller, less systematic effect was found when reinforcers were arranged dependently and probabilistically. These findings highlight the importance of reinforcement contingencies and contingency discriminability in remembering, and add to the evidence showing that cues signaling differential reinforcement in DMTS may affect processes during the retention interval and comparison phase, rather than attention to the sample stimulus. • We investigated how brief cues signaling the presence or absence of reinforcers affect memory performance. • Cues were presented for 0.5 s after the sample in a delayed matching-to-sample procedure. • In reinforced trials, reinforcers were arranged with p =.5 (Expt 1) or for all correct responses (Expt 2). • Accuracy was lower when cues signaled reinforcer absence in Expt 2. This effect was smaller and less systematic in Expt 1. • These findings highlight the role of discriminated reinforcement contingencies in remembering. [ABSTRACT FROM AUTHOR]

We recently found that initial-link stimuli signaling trial outcomes (signals) in a concurrent-chains procedure exerted imperfect control during initial and terminal links. Here, we conducted a follow-up experiment to investigate further such imperfect control. Five pigeons worked on a concurrent-chains procedure in which one alternative led to a terminal link ending in a smaller-sooner reinforcer delivery, and the other in a larger-later reinforcer. During initial links of some trials, compound stimuli (signals) signaled the trial outcome. We assessed control by signal dimensions in Conflicting trials, in which the dimensions signaled conflicting outcomes. Unlike our previous experiment, signals remained present during terminal links. During initial links, preference favored the signaled key in Signaled trials, and the key signaled by the dimension exerting stronger control in Conflicting trials, suggesting strong signal control. Initial-link choice also depended on trial outcomes; preference was overall biased towards the smaller-sooner key. Terminal-link responding was primarily controlled by the key peck producing terminal-link entry, although some weak signal control was also evident. Thus, signal control during initial and terminal links was enhanced, and control by key-peck location during terminal links persisted, when signals remained present during terminal links. This suggests that our previous findings were partly related to temporal separation between signals and trial outcomes, and to history effects producing strong control by key-peck location. • We investigated how temporal separation between stimuli and outcomes affects stimulus control. • Pigeons responded for differentially signaled, delayed outcomes in a concurrent-chains procedure. • Behavior was controlled by the signals, and by key-peck location. • Signal control was stronger when the signals remained present until the outcome. • Interoceptive cues such as key-peck location may help bridge the gap between stimuli and future outcomes. [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]