The substitutability of reinforcers

Substitutability is a construct borrowed from microeconomics that describes a continuum of possible interactions among the reinforcers in a given situation. Highly substitutable reinforcers, which occupy one end of the continuum, are readily traded for each other due to their functional similarity. Complementary reinforcers, at the other end of the continuum, tend to be consumed jointly in fairly rigid proportion, and therefore cannot be traded for one another except to achieve that proportion. At the center of the continuum are reinforcers that are independent with respect to each other; consumption of one has no influence on consumption of another. Psychological research and analyses in terms of substitutability employ standard operant conditioning paradigms in which humans and nonhumans choose between alternative reinforcers. The range of reinforcer interactions found in these studies is more readily accommodated and predicted when behavior-analytic models of choice consider issues of substitutability. New insights are gained into such areas as eating and drinking, electrical brain stimulation, temporal separation of choice alternatives, behavior therapy, drug use, and addictions. Moreover, the generalized matching law (Baum, 1974) gains greater explanatory power and comprehensiveness when measures of substitutability are included.     

Category discrimination by pigeons using five polymorphous features

Eight pigeons were trained to discriminate between sets of color photographs of natural scenes. The scenes differed along five two-valued dimensions (site, weather, camera distance, camera orientation, and camera height), and all combinations of the feature values were used. One value of each dimension was designated as positive, and slides containing three or more positive feature values were members of the positive stimulus set. Thus, each feature had an equal, low, correlation with reinforcement, and all features had zero correlations with each other. Seven of the 8 pigeons learned this discrimination, and their responding came under the control of all five features. Within the positive and negative stimulus sets, response rates were higher to stimuli that contained more positive feature values. Once discrimination had been achieved, reversal training was given using a subset of the slides. In this subset, only a single feature was correlated with reinforcement. All pigeons learned this reversal successfully and generalized it to additional photographs with the same feature content. After reversal, the original reinforcement contingencies were reinstated, and training was continued using all the slides except those that had been used in reversal. Reversal generalized to these slides to some extent. Analysis of the response rates to individual slides showed that, compared with prereversal training, only the feature that had been subjected to reversal contingencies showed a reversed correlation with response rate. The remaining features showed the same correlation with response rate as they had before reversal training. Thus, reversal on some members of a category following category discrimination training led to generalization to stimuli within the category that were not involved in the reversal, but not to features that were not reversed. It is therefore inappropriate to refer to the pigeons as learning a concept.     

环境伦理学

一、导论面对“环境危机”,环境哲学家们有一种相当普遍的共识,即应该从伦理学的角度来考察环境问题。他们一致认为,环境问题是重要的,但它在过去没有得到足够的重视。同样,他们也一致认为,在我们处理环境问题时,伦理学应起到更大的作用。然而,也有不一致的地方,即环境伦理学是由什么组成的,怎样才能实现它,在什么程度上实现它是理想的。本文考察当个环境伦理学的关键问题。价值观和对环境及为环境所采取的行动深深地被我们对环境的观察与理解影响着。因此,本文一开始叙述了在过去的一个世纪里,在环境问题上,科学对环境问题的…     

Evidence Supporting the Importance of Peripheral Visual Information for the Directional Control of Aiming Movement

The focus of the present study was on determining whether the high level of directional accuracy found in aiming studies in which the subjects can see their hand in the visual periphery supports the existence of a kinetic visual channel or, rather, the advantage of binocular over monocular vision for movement directional control. The limits of this kinetic visual channel were also explored. The results of the 1st experiment indicated that seeing one's hand in the visual periphery is sufficient to ensure optimal directional aiming accuracy. Further, no differences in aiming accuracy were noted between monocular and binocular vision. These results supported the existence of a visual kinetic channel. In the 2nd experiment, whether this kinetic visual channel would operate with movements slower (55 degrees /s) than those usually used in studies that had proved its existence (over 110 degrees /s) was delineated. The results indicated that this visual kinetic channel was operative even at relatively slow movement velocities. Central vision of the hand seemed to be used for on-line directional control of relatively slow movements.     

试答无法回答的问题

试答无法回答的问题让·多尔梅松著萧俊明译联合国教科文组织去年在巴黎以“我们不知道什么？”为主题召开了第一届哲学座谈会,取得了巨大的成功。《第欧根尼》第１６９期刊登了一些与会者的论文。第二届会议于１９９６年３月２７—３０日召开,讨论的问题如同前一届一样...     

Women,ectogenesis and ethical theory

ABSTRACT The nature of two influential theories on the moral status of abortion logically commits them to welcoming the advent of ectogenesis (the gestation of human beings outside the womb) as a solution to the abortion conflict. However, qualitative research into women's response to ectogenesis reveals that both women in favour and women opposed to abortion rights reject the technology on surprisingly similar grounds. The abortion framework which led women to reject ectogenesis as an ethical resolution to unwanted pregnancy is contrasted with the moral framework which shapes formal ethical discussions of abortion. It is argued that the need for ethical relevance requires the views of ethicists to move closer to those of women [1].     

开放的中国──封闭的中国

禁地,亦即指由于地形原因而不可进入的地区,尤其是指出于政治、宗教或其他动机而作出的决策所禁止入内的区域（场所、城市、国家）。禁地往往蒙上了一种神秘的气氛．几乎必然会引起人们的好奇。到达拉萨曾是几代探险家的梦想。这一地区不仅对外人封闭,而且对“内部人”也封闭：任何人不得离开“外出”。德川幕府对日本实行的隔绝就是这样一种双向隔离。当然．地理条件也有助于这种隔离,因而使之轻易地付诸实行。有人指出（或许这种说法不够严肃）．举世闻名的中国长城不仅意味着防范匈奴入侵,更意味着防止中国人逃离。史料也表明中国过…