Second-order schedules of token reinforcement with pigeons: effects of fixed- and variable-ratio exchange schedules

Pigeons' key pecks produced food under second-order schedules of token reinforcement, with light-emitting diodes serving as token reinforcers. In Experiment 1, tokens were earned according to a fixed-ratio 50 schedule and were exchanged for food according to either fixed-ratio or variable-ratio exchange schedules, with schedule type varied across conditions. In Experiment 2, schedule type was varied within sessions using a multiple schedule. In one component, tokens were earned according to a fixed-ratio 50 schedule and exchanged according to a variable-ratio schedule. In the other component, tokens were earned according to a variable-ratio 50 schedule and exchanged according to a fixed-ratio schedule. In both experiments, the number of responses per exchange was varied parametrically across conditions, ranging from 50 to 400 responses. Response rates decreased systematically with increases in the fixed-ratio exchange schedules, but were much less affected by changes in the variable-ratio exchange schedules. Response rates were consistently higher under variable-ratio exchange schedules than tinder comparable fixed-ratio exchange schedules, especially at higher exchange ratios. These response-rate differences were due both to greater pre-ratio pausing and to lower local rates tinder the fixed-ratio exchange schedules. Local response rates increased with proximity to food under the higher fixed-ratio exchange schedules, indicative of discriminative control by the tokens.     

Behavioral and pharmacological variables affecting risky choice in rats.

The effects of manipulations of response requirement, intertrial interval (ITI), and psychoactive drugs (ethanol, phencyclidine, and d-amphetamine) on lever choice under concurrent fixed-ratio schedules were investigated in rats. Responding on the "certain' lever produced three 45-mg pellets, whereas responding on the "risky" lever produced either 15 pellets (p = .33) or no pellets (p .67). Rats earned all food during the session, which ended after 12 forced trials and 93 choice trials or 90 min, whichever occurred first. When the response requirement was increased from 1 to 16 and the ITI was 20 s, percentage of risky choice was inversely related to fixed-ratio value. When only a single response was required but the ITI was manipulated between 20 and 120 s (with maximum session duration held constant), percentage of risky choice was directly related to length of the ITI. The effects of the drugs were investigated first at an ITI of 20 s, when risky choice was low for most rats, and then at an ITI of 80 s, when risky choice was higher for most rats. Ethanol usually decreased risky choice. Phencyclidine did not usually affect risky choice when the ITI was 20 s but decreased it in half the rats when the ITI was 80 s. For d-amphetamine, the effects appeared to he related to baseline probability of risky choice; that is, low probabilities were increased and high probabilities were decreased. Although increase in risky choice as a function of the ITI is at variance with previous ITI data, it is consistent with foraging data showing that risk aversion decreases as food availability decreases. The pharmacological manipulations showed that drug effects on risky choice may be influenced by the baseline probability of risky choice, just as drug effects can be a function of baseline response rate.     

循证医学的辩证思维

随着临床医学的发展,临床医生面临着从理论知识加个人经验的医学模式向以科学证据为基础的医学模式转变。越来越多的卫生政策和诊疗指南的制定需要以高质量的研究结果为依据,如随机对照研究的结果,特别是随机对照研究的系统综述结论。循证医学模式要求医生在临床工作中不断提出问题并通过严格的科研设计来回答这些问题,同时强调不断进行知识更新,掌握最新研究证据以指导其临床工作。同时政府部门也鼓励发展循证医疗,因为它可通过研究有效的诊疗手段来提高卫生保健的效率。此外还有迹象表明法律决策过程中要参考是否遵循了研究证据和临床指南。知情的服务对象也促使临床工作者寻求研究证据作为依据,为了提高服务质量并且充分把握特殊专业领域的现状,临床工作者也需要不断了解新的依据信息。在众多的研究信息中,我们应对每项证据的研究方法、研究对象及观察的终点进行认真分析,确定该结论是否真实并适合我们的实际,从而制定有据可查的诊疗方案。     

Embodied Knowledge and Making Sense of Prenatal Diagnosis

Open-ended, qualitative interviews with women to whom amniocentesis was offered were analyzed to understand how women made sense of these tests. We found that women, whether tested or not, negotiated with biomedical information. They transformed it through identifiable processes, then wove it with their own instincts and beliefs and with their personal experiences, thereby creating embodied knowledge on which their decisions were based. Women who were and were not tested may have differed from each other when categorized on the basis of a final, binary choice, but they were more alike than unalike in reaching this point. The apparent importance of embodied knowledge suggests the critical role of the listening activities of the genetic counselor and of awareness of the validity and importance of women's complementary ways of knowing and doing in understanding the uses and meanings of prenatal genetic testing.     

The influence of adults' actions on children's inferences about word meanings

This article first establishes the effect of adults' actions on children's inferences about the shape and material of solid objects, based on data from Japanese 2-, 4-, and 6-year-olds. Japanese 2-year-olds are already sensitive to adults' actions in making inferences, and children become more adept at this as they become older. The invariance of the phenomenon of the effect of actions is then discussed in terms of three of its aspects: across age groups, across languages (the universality of the effect), and across tasks in lexical development. It is suggested that while specific linguistic characteristics (e.g., the means of individuation of entities), and complexity of object shape probably influence the effect of actions, action effects may have a potentially invariant/universal aspect.     

A Bootstrapping Model of Frequency and Context Effects in Word Learning

Prior research has shown that people can learn many nouns (i.e., word–object mappings) from a short series of ambiguous situations containing multiple words and objects. For successful cross‐situational learning, people must approximately track which words and referents co‐occur most frequently. This study investigates the effects of allowing some word‐referent pairs to appear more frequently than others, as is true in real‐world learning environments. Surprisingly, high‐frequency pairs are not always learned better, but can also boost learning of other pairs. Using a recent associative model (Kachergis, Yu, & Shiffrin, 2012), we explain how mixing pairs of different frequencies can bootstrap late learning of the low‐frequency pairs based on early learning of higher frequency pairs. We also manipulate contextual diversity, the number of pairs a given pair appears with across training, since it is naturalistically confounded with frequency. The associative model has competing familiarity and uncertainty biases, and their interaction is able to capture the individual and combined effects of frequency and contextual diversity on human learning. Two other recent word‐learning models do not account for the behavioral findings.     

Identification With All Humanity: The role of self‐definition and self‐investment

Identification With All Humanity (IWAH) relates to higher levels of concern and supportive behavior toward the disadvantaged, stronger endorsement of human rights, and stronger responses in favor of global harmony. So far, IWAH has been conceptualized as a one‐dimensional construct describing the degree with which one identifies with all humans as a superordinate ingroup. However, recent group identification models suggest a multi‐dimensional model to provide a more differentiated approach toward the understanding of the highest level of social identification. Using principal axis (Study 1) and confirmatory (Study 2) factor analyses, we suggest that IWAH sub‐divides into two dimensions—global self‐definition and global self‐investment. Study 2 revealed that global self‐investment was a stronger predictor for both convergent measures (e.g., social dominance orientation and authoritarianism) and behavioral intentions than global self‐definition. Finally, in Study 3, we manipulated IWAH to test its causal effect on donation behavior. Participants in the experimental condition, compared with the control condition, showed higher global self‐investment, which in turn predicted greater giving to global charity. These findings suggest that two dimensions with different behavioral outcomes underlie IWAH.     

Structuring Case-Based Ethics Training: How Comparing Cases and Structured Prompts Influence Training Effectiveness

This study examined how structuring case-based ethics training, either through (a) case presentation or (b) prompt questions, influences training outcomes. Results revealed an interaction between case presentation and prompt questions such that some form of structure improved effectiveness. Specifically, comparing cases led to greater sensemaking strategy use and decision-ethicality when trainees considered unstructured rather than structured prompts. When cases were presented sequentially, structuring prompts improved training effectiveness. Too much structure, however, decreased future ethical decision making, suggesting that there can be too much of a good thing when structuring case-based ethics education. Implications for designing ethics training programs are discussed.     

Laterality effects in the spinning dancer illusion: The viewing‐from‐above bias is only part of the story

The ‘silhouette illusion’, representing the silhouette of a female dancer pirouetting about her vertical axis, is a bistable stimulus created by Japanese web designer Nobuyuki Kayahara. Although the dancer can be perceived as spinning either clockwise or counterclockwise, the clockwise rotation is usually preferred. Troje and McAdam (i‐Perception, 2010, 1, 143) showed that this clockwise bias can be attributed to the tendency to assume a viewpoint from above rather than from below, given that the dancer is portrayed from a vantage point that is not perpendicular to the axis of rotation. Here, we tested whether another possible factor contributing to the observers’ interpretation of this bistable stimulus might be the tendency to perceive movements of the right rather than the left foot. We confirmed both the viewing‐from‐above bias and our hypothesis. The bias to perceive movements of the right leg might be a generalization to lower limbs of a perceptual frequency effect already observed for upper limbs. Such a perceptual and attentional bias towards the right hand/foot could account for the greater ability to predict the outcome of sport actions when observing right‐ rather than left‐limbed movements, and thus the left‐handers' and left‐footers' advantage observed in a variety of interactive sports.     

A Computational Evaluation of Sentence Processing Deficits in Aphasia

Individuals with agrammatic Broca's aphasia experience difficulty when processing reversible non‐canonical sentences. Different accounts have been proposed to explain this phenomenon. The Trace Deletion account (Grodzinsky, 1995, 2000, 2006) attributes this deficit to an impairment in syntactic representations, whereas others (e.g., Caplan, Waters, Dede, Michaud, & Reddy, 2007; Haarmann, Just, & Carpenter, 1997) propose that the underlying structural representations are unimpaired, but sentence comprehension is affected by processing deficits, such as slow lexical activation, reduction in memory resources, slowed processing and/or intermittent deficiency, among others. We test the claims of two processing accounts, slowed processing and intermittent deficiency, and two versions of the Trace Deletion Hypothesis (TDH), in a computational framework for sentence processing (Lewis & Vasishth, 2005) implemented in ACT‐R (Anderson, Byrne, Douglass, Lebiere, & Qin, 2004). The assumption of slowed processing is operationalized as slow procedural memory, so that each processing action is performed slower than normal, and intermittent deficiency as extra noise in the procedural memory, so that the parsing steps are more noisy than normal. We operationalize the TDH as an absence of trace information in the parse tree. To test the predictions of the models implementing these theories, we use the data from a German sentence—picture matching study reported in Hanne, Sekerina, Vasishth, Burchert, and De Bleser (2011). The data consist of offline (sentence‐picture matching accuracies and response times) and online (eye fixation proportions) measures. From among the models considered, the model assuming that both slowed processing and intermittent deficiency are present emerges as the best model of sentence processing difficulty in aphasia. The modeling of individual differences suggests that, if we assume that patients have both slowed processing and intermittent deficiency, they have them in differing degrees.