Behavioral control by the response–reinforcer correlation

Using a discrete‐trials procedure, two experiments examined the effects of response–reinforcer correlations on responding while controlling molecular variables that operated at the moment of reinforcer delivery (e.g., response–reinforcer temporal contiguity, interresponse times preceding reinforcement). Each trial consisted of three successive components: Response, Timeout, and Reinforcement, with the duration of each component held constant. The correlation between the number of responses in the Response component and reinforcer deliveries in the Reinforcement component was varied. In the Positive‐correlation condition, a larger number of responses in the Response component programmed a higher reinforcement rate (Experiment 1) or a shorter time to reinforcement (Experiment 2) in the Reinforcement component. Although programmed in this way, the actual reinforcer delivery was dependent on, and occurred immediately after, a response in the Reinforcement component. In the Zero‐correlation condition, the programmed rates of reinforcement (Experiment 1) or the times to reinforcement (Experiment 2) in the Reinforcement component of each trial were yoked to those in the preceding Positive‐correlation condition. Responding in the Response component was higher in the Positive‐ than in the Zero‐correlation condition, without systematic changes in molecular variables. The results suggest that the response–reinforcer correlation can be a controlling variable of behavior.     

Predator videos and electric shock function as punishers for zebrafish (Danio rerio)

Zebrafish (Danio rerio) are a promising animal model for studying the effects of gene–environment interactions on behavior. Two experiments were conducted to assess punishment effects of presenting predator videos (Indian leaf fish; Nandus nandus) and electric shock on operant approach responses in zebrafish. In Experiment 1, the predator video and shock stimuli were presented upon a response maintained by a single variable‐interval schedule of food reinforcement in different groups of fish. In Experiment 2, the predator video and shock stimuli were presented upon one of two response alternatives maintain by concurrently available variable‐interval schedules of food reinforcement in different groups of fish. Responding decreased when the predator video and shock stimuli were presented relative to their absence in both experiments. Moreover, responding on an unpunished alternative did not reliably decrease in Experiment 2. These results indicate that the decrease in responding resulted from the punishment contingency rather than from elicited species‐specific defense responses or conditioned avoidance. Thus, the predator video and electric shock functioned as punishers of operant behavior for zebrafish. Identifying punishers for this species could lead to research on how gene–environment interactions influence individual differences in sensitivity to punishment.     

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Dysfunctional Attitudes Lead to Depressive Symptoms by Generating Subjective Stress

Previous studies have indicated that objective stress—negative events that have actually occurred outside of individuals—is involved in processes of dysfunctional attitudes leading to depression. Subjective stress—individuals' perception of negative events that have not actually occurred outside of them—is also predicted to be involved in these processes. However, few studies have empirically investigated this prediction. The primary purpose of this study was to fill this gap by testing the hypothesis that dysfunctional attitudes lead to depression by generating subjective stress. A longitudinal design was employed and initial depression was controlled. The results supported the hypothesis. It was also found that initial depression fostered subsequent depression by generating subjective stress. This study contributes to the literature on depression mechanisms by elucidating that subjective stress plays an important role in the development and exacerbation of depression. This study also has important clinical implications as it suggests that preventing subjective stress in individuals with dysfunctional attitudes or depression helps to protect the development or exacerbation of their depression.     

Zebrafish choice behavior is sensitive to reinforcer rate,immediacy, and magnitude ratios

Behavioral flexibility has, in part, been defined by choice behavior changing as a function of changes in reinforcer payoffs. We examined whether the generalized matching law quantitatively described changes in choice behavior in zebrafish when relative reinforcer rates, delays/immediacy, and magnitudes changed between two alternatives across conditions. Choice was sensitive to each of the three reinforcer properties. Sensitivity estimates to changes in relative reinforcer rates were greater when 2 variable-interval schedules were arranged independently between alternatives (Experiment 1a) than when a single schedule pseudorandomly arranged reinforcers between alternatives (Experiment 1b). Sensitivity estimates for changes in relative reinforcer immediacy (Experiment 2) and magnitude (Experiment 3) were similar but lower than estimates for reinforcer rates. These differences in sensitivity estimates are consistent with studies examining other species, suggesting flexibility in zebrafish choice behavior in the face of changes in payoff as described by the generalized matching law.     

The role of adventitious reinforcement during differential reinforcement of other behavior: A systematic replication

Differential reinforcement of other behavior (DRO) is commonly used to decrease problem behavior by presenting reinforcers contingent upon the absence of a target response. Although it is well demonstrated that DROs decrease response rates, the processes producing these decreases are not well understood. The present study systematically replicated previous research assessing whether adventitious reinforcement of alternative behavior contributes to the effectiveness of DRO. We presented university students with two options on a computer and reinforced target responding on a variable-ratio schedule. Next, we compared decreases in target-response rates and any increases in alternative responding during DRO schedules versus yoked variable-time schedules or extinction probes. DRO schedules resulted in the lowest target-response rate and highest alternative-response rate. These findings generally provide some support for the adventitious reinforcement of “other” behavior.     

Adventitious reinforcement during long-duration DRO exposure

Differential reinforcement of other behavior (DRO) is a procedure often used to decrease problem behavior, but the processes responsible for behavior reduction are not well understood. This study assessed whether adventitious reinforcement of other behavior contributes to DRO effectiveness when, relative to previous research, DRO exposure is prolonged. Two response options were presented on a computer and target responding was reinforced on a variable-ratio schedule. Response rates were then compared during DRO versus yoked variable-time or extinction probes. Across 2 experiments, DRO decreased target responding and increased other responding more than control conditions. However, increases in other responding did not usually maintain despite target responding remaining at low levels. DRO might adventitiously reinforce other responses transiently but the decreases in target behavior could not be entirely explained by adventitious reinforcement of the other response. Instead, reductions in target responding likely depend on the discriminability of the DRO contingency.     

Discrimination of two neighboring intra- and intermodal empty time intervals marked by three successive stimuli

We investigated the discrimination of two neighboring intra- or inter-modal empty time intervals marked by three successive stimuli. Each of the three markers was a flash (visual—V) or a sound (auditory—A). The first and last markers were of the same modality, while the second one was either A or V, resulting in four conditions: VVV, VAV, AVA and AAA. Participants judged whether the second interval, whose duration was systematically varied, was shorter or longer than the 500-ms first interval. Compared with VVV and AAA, discrimination was impaired with VAV, but not so much with AVA (in Experiment 1). Whereas VAV and AVA consisted of the same set of single intermodal intervals (VA and AV), discrimination was impaired in the VAV compared to the AVA condition. This difference between VAV and AVA could not be attributed to the participants' strategy to perform the discrimination task, e.g., ignoring the standard interval or replacing the visual stimuli with sounds in their mind (in Experiment 2). These results are discussed in terms of sequential grouping according to sensory similarity.