Choice between repleting/depleting patches: A concurrent-schedule procedure

Six pigeons responded on two concurrently available keys that defined patches with the following characteristics. Reinforcer stores repleted on a patch as a linear function of time when the bird had last responded to the other patch, or else did not replete. Repletion schedules thus timed only when the bird was absent from the patch. Reinforcer stores on a patch could be depleted and reinforcers obtained, again as a linear function of time, when the bird responded on a key. Depletion schedules thus timed only when the birds were present at a patch. Experiment 1 investigated changing relative depletion rates when repletion rates were constant and equal (Part 1) and changing relative repletion rates when the depletion rates were constant and equal (Part 2). Response- and time-allocation ratios conformed to a generalized matching relation with obtained reinforcer ratios, and there appeared to be no control by the size of the reinforcer stores. In Experiment 2, absolute depletion rates were varied with a pair of unequal repletion rates (Part 3), and absolute repletion rates were varied with a pair of unequal depletion rates (Part 4). Dwell times in the patches were not affected by either variation. Melioration theory predicted the results of Experiment 1 quite closely but erroneously predicted changing dwell times in Experiment 2. Molar maximization theory did not accurately predict the results of either experiment.     

Fixed-ratio pausing: Joint effects of past reinforcer magnitude and stimuli correlated with upcoming magnitude

Pigeons responded on fixed-ratio schedules ending in small or large reinforcers (grain presentations of different duration) interspersed within each session. In mixed-schedule conditions, the response key was lit with a single color throughout the session, and pausing was directly related to the past reinforcer (longer pauses after large reinforcers than after small ones). In multiple-schedule conditions, different colors accompanied the ratios ending in small and large reinforcers, and pausing was affected by the upcoming reinforcer as well as the past one. Pauses were shorter before large reinforcers than before small ones, but they continued to be longer after large reinforcers than after small ones. The influence of the past reinforcer was modulated by the magnitude of the upcoming reinforcer; in the presence of the stimulus before the small reinforcer, the effect of the past reinforcer was enhanced relative to its effect in the stimulus before the large reinforcer. These results show that pausing between ratios is jointly determined by two competing factors: past conditions of reinforcement and stimuli correlated with upcoming conditions.     

Discriminability between alternatives in a switching-key concurrent schedule

Six pigeons were trained to discriminate between two intensities of white light in a symbolic matching-to-sample procedure. These stimuli were then used to signal which schedule was available on the main key in a switching-key concurrent schedule. The concurrent schedules led to a symbolic matching-to-sample phase in which the subject identified the concurrent schedule to which it last responded before a reinforcer could be obtained. The concurrent schedules were varied across conditions. Discriminability, measured during the symbolic matching-to-sample performance, was high throughout and did not differ across the two procedures. Performance in the concurrent schedules was like that typically obtained using these schedules. Delays were then arranged between completion of the concurrent schedules and presentations of the symbolic matching-to-sample phase. A series of conditions with an intervening delay of 10 s showed that both concurrent-schedule performance and symbolic matching-to-sample performance were affected by the delay in a similar way; that is, choice responding was closer to indifference.     

Effects of reinforcer delays on choice as a function of income level

Three rats earned their daily food ration by responding during individual trials either on a lever that delivered one food pellet immediately or on a second lever that delivered three pellets after a delay that was continuously adjusted to ensure substantial responding to both alternatives. Choice of the delayed reinforcer increased when the number of trials per session was reduced. This result suggests that models seeking closure on choice effects must include a parameter reflecting how preference changes with sessionwide income. Moreover, models positing that reinforcer probability and immediacy (1/delay) function equivalently in choice are called into question by the finding that probability and immediacy produce opposing effects when income level is changed.     

Cultural practices of Hispanics: implications for the prevention of AIDS

Hispanic Americans have one of the highest rates of HIV seroprevalence among all ethnics groups in the US, with high rates being especially noticeable among women and children. Were it known which cultural factors have the most influence on whether Hispanics engage in high-risk behavior for HIV transmission, prevention interventions could be targeted accordingly. To that end, this study was mounted to identify which Hispanic cultural factors relate to condom use. 117 males and 73 females aged 17-56 years of mean age 25.67 were surveyed in Washoe county, Nevada. These mostly young adults had recently immigrated to the western US. It was initially posited that fate orientation, male- female relationships, family relationships, machismo behavior, and religion would have equal influence with respect to condom use. Analysis found that condom use was largely associated with and determined by men who are the principal buyers of condoms. A machismo attitude toward protecting women by using condoms was also associated with condom use. Neither fate orientation with respect to AIDS, nor religion were important determinants of condom use, even though 86.5% of the respondents were Catholic. The degree to which respondents adhered to traditional Hispanic cultural values was influenced by the degree of education and acculturation. On the basis of these findings, the authors suggest targeting AIDS prevention messages to males, while emphasizing the protection of women through condom use. They also suggest that both education and acculturation levels be assessed before implementing prevention programs.     

The relationship between attitude,assertiveness and condom use

The Australian study investigated condom-specific assertiveness and condom use as a means of prevention infection from sexually transmitted diseases. 211 men participated including 83 homosexual men (aged 19-62 years) and 128 heterosexual men (aged 17-49) who completed a questionnaire that comprised demographic details such as age, monogamy, and sexual activity as well as attitudinal and assertiveness measures. General assertiveness was measured by the Rathus Assertiveness Schedule (RAS) which had been widely used across a wide range of social situations. Assertiveness relating specifically to situations involving condoms was measured by the Condom Assertiveness Scale (CAS). Intention to use condoms was positively related to favorable attitudes, which were related to condom-specific assertiveness for both groups. For the heterosexual men only, general social assertiveness was negatively related to attitudes toward condoms. For both groups, the condom-specific measure of assertiveness was positively correlated with attitudes toward condoms. Condom-specific assertiveness was positively related to general social assertiveness as measured by the Rathus Assertiveness Schedule for the homosexual, but not for the heterosexual men. The negative relationship between general assertiveness and attitude to condoms among the heterosexual men implies that the risk reducing behavior of condom use did not seem to accord with the perceptions of masculinity and social assertiveness among heterosexual men. Thus, female partners of such heterosexual men exhibiting negative attitudes toward condom use combined with assertiveness would have to overcome resistance to insist on the use of condoms. Recently some advertising campaigns have been directed at women. The promotion of condom use among heterosexual men has to deal with the perceptions of condom use as unmasculine behavior.     

The legal consensus about foregoing life-sustaining treatment: its status and its prospects

The legal consensus that has evolved through adjudication and legislation since the Karen Quinlan case in 1976 is founded on the premise that there is a bright line between passive euthanasia and active euthanasia. Indeed, the term passive euthanasia is often eschewed in favor of less emotionally-laden terminology such as "forgoing life-sustaining treatment" or "terminating life support" so as to further sever any possible connection with active euthanasia. Legal approval has been bestowed upon passive euthanasia under certain circumstances while active euthanasia is routinely condemned. This consensus was put to a test in 1990 when the United States Supreme Court ruled on the Cruzan case. However, the Court's narrow decision did not upset the consensus, and in the most significant appellate decisions handed down by state courts since Cruzan, there has been a reaffirmation--and possibly even an extension--of the consensus. Two other threats to the legal consensus about forgoing life-sustaining treatment have begun to manifest themselves: the increasing pressure for mercy killing and "futility" cases. Both of these challenge the fundamental premises on which the consensus is grounded.     

心身问题与心灵哲学

第9届维特根斯坦国际专题讨论会的主题是心灵哲学(philosophy of mind,或译心智哲学)和心理学哲学。详细地讨论过的问题包括:心身问题、心灵哲学的传统问题和心理学哲学。 1.心身问题什么是心身问题?“心灵”(mind)一词有多种非常不同的用法,这一事实导致了现代讨论中的某种混乱。对这个词,我们至少可以区分出五种不同的用法,因此心身问题至少有五种意义。 (1)我们可以象笛卡儿使用“mens”一词那样使用“心灵”一词,让它指称具有心理属性的东西,亦即指称那种能思想,能感知,能相信和能欲求的东西。在这种情况下,我们通常是用“心灵”这个词意指“人”这个词所意指的东西,因而该词表示的就是你和我这样一些实     

库恩的可否证性模式

库恩和拉卡托斯都不同意把理论的评价看作是理论的可证实性或理论的可否证性这一传统观点。他们的批判分为两个题目:首先,一种科学理论并非只能凭经验的结果来检验;其次,人们不会在没有现成可替代的理论时就摈弃一种理论。在拉卡托斯的术语里,要么被接受,要么被摈弃的是理论的研究纲领而不仅仅是理论本身。进一步说,某一特定的范式或研究纲领的摈弃并不就是简单地被取代,一种替代范式在另一种范式或研究纲领被摈弃之前必须发生效用。最近,人们对拉卡托斯夸大第二点进行了批判。F.M.亚克罗德认为,在科学史上有一些情况是,一项研究被简单地摈弃了,而且的确是被合理地摈弃了,尽管还没有替代者。在本文中,我