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Much research has documented rate matching in concurrent variable‐interval schedules, but comparatively little research has examined performance in concurrent variable‐ratio schedules, except in discrete‐trials procedures that sometimes produce probability matching. One should expect that the two types of schedule would result in different performances, because ratio schedules cannot improve with time the way interval schedules do; ratio schedules lack the temporal dynamics of interval schedules. The present experiment exposed rats to concurrent variable‐ratio schedules. Seven unsignaled components were presented in random order within each daily session, with probability ratios ranging from 1:8 to 8:1. Three conditions were studied that varied the overall probability of food while leaving probability ratios the same. Choice appeared to conform to probability matching, because sensitivities in the rate–matching relation were close to 0.5, whereas sensitivities to probability ratio were close to 1.0. The sensitivities alone, however, could not confirm probability matching, because undermatching to rate occurs often. Analyses at smaller time scales supported the interpretation of probability matching. In particular, control by food deliveries was highly local in concurrent variable‐ratio schedules, in contrast with concurrent variable‐interval schedules, in which control is extended. Activity continued to switch between alternatives throughout components, contradicting optimal sampling theory.

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Many approaches for reducing unwanted behavior use punishment, extinction, or noncontingent reinforcement. Other methods focus on teaching and reinforcing alternative behaviors that can replace the unwanted behavior. Another strategy can be to change the stimulus control of the unwanted behavior. The present study investigated if conditional discrimination training using positive reinforcement could reduce undesirable behaviors in a pet dog. After conditional discrimination training, two unwanted behaviors (jumping and mouthing) occurred reliably in the presence of new discriminative stimuli, while other behaviors occurred in the presence of the discriminative stimuli that had previously produced these unwanted behaviors. This experiment demonstrates that conditional discrimination training can be an effective way to control the frequency of an unwanted behavior by controlling the frequency of the presentation of a discriminative stimulus.

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Equivalence classes are defined according to the substitutability, or functional similarity, of the stimuli within a stimulus class. Several studies have demonstrated that the degree of functional similarity between stimuli in a class is dependent, in part, upon the number of nodes (intervening stimuli) between the stimuli. Higher nodal number is related to lower functional similarity. This effect is referred to as “nodality.” There are three key factors that have not been simultaneously controlled for in the relevant studies: priming effects, reinforcement during training, and multiple stimulus functions of stimuli (sample, comparison, or both). In the present experiment, controlling for these factors, two 6‐member, 4‐node equivalence classes were established, and a within‐class preference assessment was used to evaluate nodality. Of 12 participants, five achieved criterion accuracy (90%) during testing. These participants demonstrated nodality, showing preference for stimuli that were nodally proximal to a sample in the preference test. When distal comparisons were chosen, participants took longer, on average, to make the selection compared to selections of proximal stimuli. These findings are consistent with earlier studies demonstrating nodality, which suggests that nodality is a robust phenomenon and not an artifact of the factors that were controlled for in the present study.

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Individuals diagnosed with autism spectrum disorder (ASD) tend to display restricted, repetitive behaviors and deficits in social interaction. Rats exposed to valproate (VPA) in utero have been shown to model symptoms of ASD. In previous research, VPA rats engaged in less social interaction and more repetitive responding than controls. The purpose of the present study was to further investigate behavioral variability in the VPA rat model of ASD by testing VPA and control rats in a reinforced‐behavioral‐variability operant task. In this procedure, rats emitted sequences of lever presses, some of which produced food. During baseline, food was delivered probabilistically, and variability was not required. Next, rats were exposed either to a variability contingency, in which food was only delivered following sequences that differed sufficiently from previous sequences (i.e., variability required), or to a yoked contingency, in which variability was not required. We hypothesized that VPA rats would behave less variably than controls in this task. However, VPA and control rats responded similarly variably when variability was required. Furthermore, VPA rats behaved slightly more variably than controls during baseline and yoked conditions, when variability was not required. These findings contribute to the complex literature surrounding the VPA rat model of ASD.

Positive reinforcement is becoming more common in horse training. Identifying effective reinforcers is critical for training success. The aim of this study was to determine relative reinforcer efficacy of different grains. Four horses learned to muzzle touch a target, after which they were tested using a progressive ratio schedule of reinforcement with different grains as the consequence. Break points were used to determine relative reinforcer efficacy of each grain and were also converted into unit price per kilocalorie to determine if caloric value impacted reinforcer efficacy. Condition 1 compared three textured grains that spanned industry‐accepted standards of low to high nonstructural carbohydrate content. Condition 2 compared three pelleted grains that similarly differed in nonstructural carbohydrate content, comparable to Condition 1, but that had a different texture than those of Condition 1. Finally, Condition 3 directly compared one grain each from Conditions 1 and 2. Results showed overall little difference in reinforcer efficacy or unit price between grains but found that all grains tested functioned as reinforcers for the horses. This suggests that a range of commercially available grains can maintain behavior and therefore be used for training. We also identified possible extraexperimental factors that impact reinforcer efficacy.