What 50 years of research tell us about pausing under ratio schedules of reinforcement

Textbooks in learning and behavior commonly describe performance on fixed-ratio schedules as “break and run,” indicating that after reinforcement subjects typically pause and then respond quickly to the next reinforcement. Performance on variable-ratio schedules, on the other hand, is described as steady and fast, with few long pauses. Beginning with Ferster and Skinner''s magnum opus, Schedules of Reinforcement (1957), the literature on pausing under ratio schedules has identified the influences on pausing of numerous important variables, in particular ratio size and reinforcement magnitude. As a result, some previously held assumptions have been called into question. For example, research has shown that the length of the pause is controlled not only by the preceding ratio, as Ferster and Skinner and others had assumed (and as implied by the phrase postreinforcement pause), but by the upcoming ratio as well. Similarly, despite the commonly held belief that ratio pausing is unique to the fixed-ratio schedule, there is evidence that pausing also occurs under variable-ratio schedules. If such widely held beliefs are incorrect, then what about other assumptions? This article selectively examines the literature on pausing under ratio schedules over the past 50 years and concludes that although there may indeed be some common patterns, there are also inconsistencies that await future resolution. Several accounts of pausing under ratio schedules are discussed along with the implications of the literature for human performances, most notably the behaviors termed procrastination.     

INCREASING OUR COMPASSION FOOTPRINT: THE ANIMALS' MANIFESTO

Our relationships with animals are wide‐ranging. When people tell me that they love animals and then harm or kill them I tell them I'm glad they don't love me. Many individuals, including scientists, ignore their responsibility when they interact with animals and fail to recognize that doing something in the name of science, which usually means in the name of humans, is not an adequate reason for intentionally causing suffering, pain, or death. “Good welfare” usually is not “good enough”. Existing regulations allow animals to be treated in regrettable ways that demean us as a species. Compassion is the key for bettering both animal and human lives. A good way to make the world a more compassionate place for animals is to increase our compassion footprint. We could begin by deciding that we will not intrude on animals' lives unless our actions are in the best interests of the animals irrespective of our desires. It is simple to make more compassionate choices about what we eat and wear and how we educate students, conduct research, and entertain ourselves at the expense of animals. The time to make these changes is long overdue.     

Stress and Adaptation

ABSTRACT— Animal models have contributed considerably to the current understanding of mechanisms underlying the role of stress in health and disease. Despite the progress made already, much more can be made by more carefully exploiting animals' and humans' shared biology, using ecologically relevant models. This allows a fundamental analysis of factors modulating individual adaptive capacity and hence individual vulnerability to disease. This article highlights an emerging scientific approach that uses a framework of interpretation that is more biologically oriented than previous approaches, to evaluate both the adaptive and maladaptive nature of the stress response in relation to existing environmental demands.     

如何评价哮喘动物模型

鉴于人体研究的局限性,动物模型在哮喘研究中起了无可替代的作用。尤其在阐明哮喘的病理生理和免疫学机制方面,动物研究可以给我们提供人体研究难以得到的结果。但是,由于人类与动物之间存在的差别,动物模型的研究结果应用于人类时还需要进一步评估。本文将对哮喘动物模型在哮喘研究中的作用及其局限性作一介绍。     

Animal Mind: Science,Philosophy, and Ethics

Although 20^th-century empiricists were agnostic about animal mind and consciousness, this was not the case for their historical ancestors – John Locke, David Hume, Jeremy Bentham, John Stuart Mill, and, of course, Charles Darwin and George John Romanes. Given the dominance of the Darwinian paradigm of evolutionary continuity, one would not expect belief in animal mind to disappear. That it did demonstrates that standard accounts of how scientific hypotheses are overturned – i.e., by empirical disconfirmation or by exposure of logical flaws – is inadequate. In fact, it can be demonstrated that belief in animal mind disappeared as a result of a change of values, a mechanism also apparent in the Scientific Revolution. The “valuational revolution” responsible for denying animal mind is examined in terms of the rise of Behaviorism and its flawed account of the historical inevitability of denying animal mentation. The effects of the denial of animal consciousness included profound moral implications for the major uses of animals in agriculture and scientific research. The latter is particularly notable for the denial of felt pain in animals. The rise of societal moral concern for animals, however, has driven the “reappropriation of common sense” about animal thought and feeling.     

PHILOSOPHERS OF INTELLECTUAL DISABILITY: A TAXONOMY

Abstract: This essay explores various roles that philosophers occupy in relation to intellectual disability. In examining how philosophers define their object of inquiry as experts and gatekeepers, it raises critical questions concerning the nature of philosophical discourse about intellectual disability. It then goes on to consider three alternate positions, the advocate or friend, the animal, and the "intellectually disabled," each of which points to new ways of philosophizing in the face of intellectual disability.     

Low-dose caffeine discrimination and self-reported mood effects in normal volunteers.

A caffeine versus placebo discrimination procedure was used to determine the lowest caffeine dose that could produce discrimination and self-reported mood effects in normal volunteers. During daily sessions under double-blind conditions, caffeine-abstinent subjects orally ingested a capsule containing 178 mg caffeine or placebo. Before beginning discrimination training, the compounds were identified to subjects by letter codes. Fifteen, 30, and 45 min after capsule ingestion, subjects guessed the capsule's letter code. Correct guesses at 45 min earned money. After each session, subjects received a supplementary capsule containing caffeine or placebo to ensure that, within each phase of the study, subjects received the same daily dose of caffeine equal to the training dose. Five of the 15 subjects acquired the caffeine versus placebo discrimination within the first 20 sessions (greater than or equal to 75% correct); 6 other subjects acquired the discrimination with additional training. Nine subjects who acquired the discrimination were subsequently trained at progressively lower caffeine doses. In general, the lowest dose to produce discrimination (greater than or equal to 75% correct) was also the lowest dose to produce self-reported mood effects: 4 subjects showed discrimination and self-reported mood effects at 100 mg caffeine, 2 at 56 mg, 1 at 32 mg, and 1 at 18 mg. One of these subjects also showed self-reported mood effects at 10 mg. The present study documents discriminative stimulus and self-reported mood effects of caffeine at doses below those previously shown to affect any behavior in normal volunteers.     

樟柳碱所致学习和记忆障碍动物模型的探讨

本实验采用水迷津法、步下法和步入法,用樟柳碱制备学习和记忆障碍的动物模型。结果表明,樟柳碱(10毫克/公斤)可使小鼠引起学习障碍,其表现为通过水迷津全程的时间延长,而且小鼠进入盲路的错误次数明显增多。樟柳碱(10毫克/公斤)可使小鼠引起记忆障碍,在樟柳碱的影响下,小鼠步下平台或步入暗箱的潜伏期明显缩短,并使它们的错误次数增多。本实验结果进一步表明,测定小鼠的记忆障碍,步入法似乎比步下法更为敏感。     

恐惧发生与预防的实验研究：──Ⅰ、强烈噪音下恐具行为的动物模型

通过不同方法对ＳＤ型大鼠分四组进行实验处理,观察比较大鼠的行为,发现：在突然的高强度噪音条件下,大鼠出现恐惧的行为反应;强刺激组大鼠恐惧行为较控制组明显增多,行为的唤醒适应能力异常,并存在显著的个体差异;噪音脱敏训练对提高大鼠在高强噪音条件下的应激能力、减少恐惧具有良好的促进作用;在脱敏训练中尤以逐渐递增噪音强度、刺激时间与平均分配实验日结合的方法效果最为显著。     

Temporal discrimination and a free-operant psychophysical procedure.

Pigeons were presented a series of keylight time periods (separated by blackouts) during which two response keys were lit, one by blue light and the other either by orange or green. Blue-key responses changed the color on the other key. Orange-key responses sometimes produced food during the first half of a time period; green-key responses sometimes produced food during the second half. In three experiments, the probability of a green-key response increased as a function of elapsed time. Experiment 1 compared performance when the duration of the keylight periods was varied across a wide range. Discrimination of performance was similar across the range of durations. Experiment 2 varied both relative reinforcement rate and the local reinforcement rate for orange-key and green-key responses. These manipulations produced changes in response bias but not discrimination sensitivity. Experiment 3 varied the local temporal placement of reinforcers within time periods and demonstrated that choice behavior was affected by differential reinforcement at different points during the time periods. The results were consistent with previous research on duration discrimination that used psychophysical trials procedures.