Choice between single and multiple reinforcers in concurrent-chains schedules

Pigeons responded on concurrent-chains schedules with equal variable-interval schedules as initial links. One terminal link delivered a single reinforcer after a fixed delay, and the other terminal link delivered either three or five reinforcers, each preceded by a fixed delay. Some conditions included a postreinforcer delay after the single reinforcer to equate the total durations of the two terminal links, but other conditions did not include such a postreinforcer delay. With short initial links, preference for the single-reinforcer alternative decreased when a postreinforcer delay was present, but with long initial links, the postreinforcer delays had no significant effect on preference. In conditions with a postreinforcer delay, preference for the single-reinforcer alternative frequently switched from above 50% to below 50% as the initial links were lengthened. This pattern of results was consistent with delay-reduction theory (Squires & Fantino, 1971), but not with the contextual-choice model (Grace, 1994) or the hyperbolic value-added model (Mazur, 2001) as they have usually been applied. However, the hyperbolic value-added model could account for the results if its calculations were expanded to include reinforcers delivered in later terminal links. The implications of these findings for models of concurrent-chains performance are discussed.     

Why pigeons say what they do: reinforcer magnitude and response requirement effects on say responding in say-do correspondence

The effects of reinforcer magnitude and response requirement on pigeons' say choices in an experimental homologue of human say-do correspondence were assessed in two experiments. The procedure was similar to a conditional discrimination procedure except the pigeons chose both a sample stimulus (the say component) and a comparison stimulus that corresponded to it (the do component). Correspondence was trained on red, green, and white key colors before the duration of food presentations following correspondence on each key color (Experiment 1) and the number of key pecks required as the say response on each key color (Experiment 2) were manipulated in an attempt to influence the initial say response. The frequency of say responses on each key color coincided with programmed changes in the duration of food presentations and the key-peck requirements assigned to each key color. Correspondence accuracy remained stable in all conditions, even those in which the say responding occurred primarily on two of the three key colors. Implications for human behavior are discussed.     

The Effect of Negative Incentives in Serial Learning: VII. Theory of Punishment

Eighty three-, four-, five-, and six-year-old boys and girls were presented with experimental conditions where context, transformational complexity, and verbal cue were varied, Two experimental tasks, a perceptually Concrete and an Abstract task, were included and Ss were assigned to a Verbal Cue or a Nonverbal Cue condition. All Ss responded to both the present progressive and the past tenses. Results revealed significant effects of the Age and Tense factors, and improved performance on Comprehension over Production. Younger children made fewer overall errors than older ones. Ss performed better on the present progressive than on the past tense on the perceptually Concrete task, while the reverse was true on the Abstract task. These findings demonstrate that language performance is the result of a complex interrelationship between transformational complexity and the perceptual properties of linguistic structures.     

History and Analysis of Delayed Discovery Statutes of Limitations in Adult Survivor Litigation

Summary

In this chapter, attorney Mary R. Williams examines how while Childhood Sexual Abuse (CSA) cases share many of the types of facts for which delayed discovery, mental incapacity, equitable estoppel and other legal statutes of limitations doctrines were created, the combination of factors of CSA cases, including unusual social dynamics and long-term psychological effects, does not fit exactly with any of these legal doctrines. She explores the historical development of delayed discovery statutes of limitations, evaluates the different types of statutes and case law, and analyzes the problematic use of the concept of repression in legislation. This chapter interprets her ground-breaking state-by-state tabulations of delayed discovery statutes of limitations and reported appellate decisions on limitations in CSA actions, published in this volume as appendices A, B, and C.     

Resurgence of goal-directed actions and habits

This study investigated how goal-directed and habitual behaviors recover after extinction within the context of the resurgence effect, a form of relapse induced by the removal or worsening of alternative reinforcement. Rats were trained to press a target lever with one reinforcer (O1) for either minimal (4) or extended (16) sessions. An extinction test after the completion of O1 devaluation confirmed that minimal and extended training formed goal-directed and habitual behaviors, respectively. Then, pressing an alternative lever was reinforced with a second reinforcer (O2) while the target response was placed on extinction. When O2 was discontinued, the minimally trained target response resurged with goal-directed status as in the extinction test. However, the extinguished habitual behavior in the extensively trained rats did not recover as a habit but instead with goal-directed status, possibly due to the context specificity of habits or the introduction of a new response–reinforcer contingency. The critical finding that reinforcer devaluation consistently led to less resurgence regardless of the amount of acquisition training provides a clinical implication that coupling differential-reinforcement-of-alternative-behavior (DRA) treatments with the devaluation of the associated reinforcer of problematic behavior could effectively diminish its recurrence.     

Response persistence under ratio and interval reinforcement schedules

In Experiment 1, rats were exposed to progressive-ratio schedules of food reinforcement while other rats were exposed simultaneously to yoked-interval schedules that arranged equivalent interreinforcer intervals but required only a single response at the end of the interval for food delivery. In Experiment 2, a within-subject yoked-control procedure was employed in which pigeons were exposed to alternating sessions (one per day) of progressive-ratio schedules and yoked-interval schedules as described above. In both experiments, responding under the yoked-interval schedule persisted beyond the point at which responding under the progressive-ratio schedule had ceased. The progressive-ratio schedules controlled break-and-run distributions, and the yoked-interval schedules controlled more even distributions of responses in time. Response rates decreased and postreinforcement pauses increased over time within individual sessions under both schedules. The results suggest that responding maintained by interval schedules is more persistent than that maintained by ratio schedules. The limitations and implications of this conclusion are discussed in the context of other investigations of response strength and behavioral momentum.     

Choice with delayed and probabilistic reinforcers: effects of prereinforcer and postreinforcer stimuli.

In Experiment 1, pigeons' pecks on a green key led to a 5-s delay with green houselights, and then food was delivered on 20% (or, in other conditions, 50%) of the trials. Pecks on a red key led to an adjusting delay with red houselights, and then food was delivered on every trial. The adjusting delay was used to estimate indifference points: delays at which the two alternatives were chosen about equally often. Varying the presence or absence of green houselights during the delays that preceded possible food deliveries had large effects on choice. In contrast, varying the presence of the green or red houselights in the intertrial intervals had no effects on choice. In Experiment 2, pecks on the green key led to delays of either 5 s or 30 s with green houselights, and then food was delivered on 20% of the trials. Varying the duration of the green houselights on nonreinforced trials had no effect on choice. The results suggest that the green houselights served as a conditioned reinforcer at some times but not at others, depending on whether or not there was a possibility that a primary reinforcer might be delivered. Given this interpretation of what constitutes a conditioned reinforcer, most of the results were consistent with the view that the strength of a conditioned reinforcer is inversely related to its duration.     

Food-deprivation level alters the effects of morphine on pigeons'' key pecking.

Four pigeons pecked response keys under a multiple fixed-ratio 30 fixed-interval 5-min schedule of food presentation. Components alternated separated by 15-s timeouts; each was presented six times. Pigeons were maintained at 70%, 85%, and greater than 90% of their free-feeding weights across experimental conditions. When response rates were stable, the effects of morphine (0.56 to 10.0 mg/kg) and saline were investigated. Morphine reduced response rates in a dose-dependent manner under the fixed-ratio schedule and at high doses under the fixed-interval schedule. In some cases, low doses of morphine increased rates under the fixed-interval schedule. When pigeons were less food deprived, reductions in pecking rates occurred at lower doses under both schedules for 3 of 4 birds compared to when they were more food deprived. When pigeons were more food deprived, low doses of morphine increased rates of pecking in the initial portions of fixed intervals by a greater magnitude. Thus, food-deprivation levels altered both the rate-decreasing and rate-increasing effects of morphine. These effects may share a common mechanism with increased locomotor activity produced by drugs and with increased drug self-administration under conditions of more severe food deprivation.     

重点中学与普通中学学生非智力因素的比较研究

本研究分别对重点中学与普通中学初一、初三年级学生的非智力因素状况进行调查,结果表明初一年级学生的非智力因素水平在两类学校之间不存在差异,而初三年级学生的非智力因素水平在两类学校之间存在着显著性差异（Ｐ＜０．０５）。随着年龄的增长,重点中学与普通中学学生的非智力因素水平都有所发展,但重点中学的学生发展得更好。本研究表明学校的教育环境影响着学生非智力因素的发展。