Choice for conditioned reinforcers in the signaled absence of primary reinforcement

Pigeons responded in a multiple schedule in which concurrent schedules of brief-stimulus presentation alternated with a component in which food was available (concurrent-chains component). In the initial links of the concurrent-chains component subjects chose either of two stimuli each correlated with the terminal link of one chain. The terminal links involved either variable-interval 30-second or variable-interval 60-second schedules. In the brief-stimulus component subjects chose between 0.5-second presentations of the terminal-link stimuli from the concurrent-chains component. Responding was generally maintained in the brief-stimulus component in two subjects for more than 300 sessions, suggesting that brief stimuli were conditioned reinforcers. During the brief-stimulus component, in 17 of 21 cases for which a minimal number of responses occurred, choice proportions above 0.55 were obtained for the brief-stimulus presentations correlated with the higher rate of primary reinforcement in the concurrent-chains component. These results support the suggestion that choice in conventional concurrent-chains procedures is partially controlled by production of the terminal-link stimuli.     

不同数学水平儿童的数量估计:图形排列方式的影响

采用参照蔡方之等(2004)所设计的图形材料,考察了不同图形排列方式对不同数学学业水平小学生数量估计的影响。35名三年级被试参加了本实验,其中优生20人,差生15人。行为数据和口头报告分析结果显示:(1)优生是更合理的数量估计者。优生数量估计的绝对误差百分比明显小于差生。(2)图形排列方式对数量估计产生了显著影响。不同图形排列方式可能会造成规则-随机数量错觉和均匀-不均匀数量错觉,从而使均匀及规则图形被高估幅度更大。     

Caregivers can implement play-based instruction without disrupting child preference

Young children diagnosed with autism spectrum disorder often require systematic teaching to learn new skills, and caregivers can teach their children by embedding learning opportunities in a play-based context. However, researchers have not evaluated procedures to train caregivers how to implement a combination of strategies designed to establish rapport and early language skills while maintaining play as a preferred context. Caregiver–child dyads composed of 2 mothers and their sons were recruited to participate. A multiple-probe design across strategies was used to demonstrate the efficacy of behavioral skills training on the mothers' integration of parallel play, child-directed interaction, teaching requests (mands), and teaching labels (tacts). Both children acquired the target requests and labels as a function of their mothers' teaching. By assessing the children's preferences, we confirmed the teaching strategies did not decrease toy engagement or the value of playing with their mother. We obtained stimulus generalization of the mothers' implementation of the strategies from a clinic to their home and maintenance of mother and child performance across a month.     

我国老龄化与老年医疗保障

中国进入21世纪面临着人口老龄化的重大课题.中国老年人口的数量及老龄化的速度在世界上都是相当高的.老龄化带来了一系列棘手的社会、经济问题,其中如何完善老年人口的医疗保障制度尤其突出.通过从我国人口老龄化的现状出发,分析现有医疗保障制度的局限性,运用系统层次理论,进一步提出建立多层次老年医疗保障体系的具体设想.即在宏观、中观、微观三个层面上,充分发挥国家与社会、社区、家庭和个人的作用,做好"老有所医"的工作.     

A molecular analysis of choice on concurrent-chains schedules.

Six pigeons responded on concurrent-chains schedules with either independent or interdependent equal variable-interval schedules in the initial links and unequal variable-interval schedules, always in a 2:1 ratio, in the terminal links. Relative response rates in the initial links increased across conditions as initial-link duration was shortened and decreased across conditions as terminal-link duration was shortened, replicating previous findings. Responses in the initial links were recorded in 5-s bins, and local or molecular relative response rates were calculated in order to ascertain how relative response rate varied as a function of time since the onset of the initial links. Two distinct molecular patterns were found. With interdependent initial links, relative response rates for the preferred key were elevated for the first 10 or 20 s of the initial links and then declined to an asymptotic value. With independent initial links, a negative recency effect was found similar to that reported by Killeen (1970). These two molecular patterns were related to the different momentary reinforcement probabilities resulting from independent and interdependent scheduling.     

Choice and foraging

In Experiment 1, six naive pigeons were trained on a foraging schedule characterized by different states beginning with a search state in which completion of a fixed-interval on a white key led to a choice state. In the choice state the subject could, by appropriate responding on a fixed ratio of three, either accept or reject the schedule of reinforcement that was offered (either a variable-interval five-second or a variable-interval 20-second). If the subject accepted the schedule, it entered a “handling state” in which the appropriate variable-interval schedule was presented. Completion of the variable-interval schedule produced food. The independent variable was the fixed-interval value in the search state, and the dependent variable was the rate of acceptance of the long variable-interval in the choice state. Experiment 2 was identical except that the search state required completion of a variable-interval, instead of a fixed-interval, schedule. The rate of acceptance of the long variable-interval schedule in both experiments was a direct function of the length of the search state, in accordance with both optimality theory and the delay-reduction hypothesis.     

Choice: Some quantitative relations

Six pigeons responded in fifty-six conditions on a concurrent-chains procedure. Conditions included several with equal initial links and unequal terminal links, several with unequal initial links and equal terminal links, and several with both unequal initial and terminal links. Although the delay-reduction hypothesis accounted well for choice when the initial links were equal (mean deviation of .04), it fit the data poorly when the initial links were unequal (mean deviation of .18). A modification of the delay-reduction hypothesis, replacing the rates of reinforcement with the square roots of these rates, fit the data better than either the unmodified delay-reduction equation or Killeen's (1982) model. The modified delay-reduction equation was also consistent with data from prior studies using concurrent chains. The absolute rates of responding in each terminal link were well described by the same hyperbola (Herrnstein, 1970) that describes response rates on simple interval schedules.     

Relative sensitivity to reinforcer amount and delay in a self-control choice situation.

Rats were exposed to concurrent-chains schedules in which a single variable-interval schedule arranged entry into one of two terminal-link delay periods (fixed-interval schedules). The shorter delay ended with the delivery of a single food pellet; the longer day ended with a larger number of food pellets (two under some conditions and six under others). In Experiment 1, the terminal-link delays were selected so that under all conditions the ratio of delays would exactly equal the ratio of the number of pellets. But the absolute duration of the delays differed across conditions. In one condition, for example, rats chose between one pellet delayed 5 s and six pellets delayed 30 s; in another condition rats chose between one pellet delayed 10 s and six pellets delayed 60 s. The generalized matching law predicts indifference between the two alternatives, assuming that the sensitivity parameters for amount and delay of reinforcement are equal. The rats' choices were, in fact, close to indifference except when the choice was between one pellet delayed 5 s and six pellets delayed 30 s. That deviation from indifference suggests that the sensitivities to amount and delay differ from each other depending on the durations of the delays. In Experiment 2, rats chose between one pellet following a 5-s delay and six pellets following a delay that was systematically increased over sessions to find a point of indifference. Indifference was achieved when the delay to the six pellets was approximately 55 s. These results are consistent with the possibility that the relative sensitivities to amount and delay differ as a function of the delays.     

Cued and uncued terminal links in concurrent-chains schedules

Pigeons were trained on a concurrent-chains schedule. The initial links were concurrent variable-interval schedules arranged on two side keys. Each terminal link was a fixed-interval schedule arranged on the center key. In cued conditions, different center-key colors signaled the two terminal-link schedules. In uncued conditions, the same center-key color appeared for both terminal links. Experiment 1 arranged unequal initial links and equal terminal links. Preference for the shorter initial-link schedule was greater when the terminal links were uncued. Experiment 2 arranged equal initial links and unequal terminal links. Preference for the shorter terminal-link schedule was greater when the terminal links were cued. Although the results of Experiment 2 successfully replicated previous research, the results of Experiment 1 are not easily reconciled with conditioned-reinforcement or discriminative-stimulus accounts of the role of terminal-link cues. Rather, terminal-link cues appear to decrease sensitivity to initial-link contingencies.     

论我国刑法妨害传染病防治罪的完善

认为妨害传染病防治罪的可罚范围有待拓宽,应将一些乙类传染病和其他突发性强、致死率高的传染病纳入本罪规制的范围;行为方式有待明确,运用刑法典与附属刑法相配合的立法模式是一种较为理想的做法;刑罚设置上有待进一步完善,增加罚金刑的适用,对后果特别严重的情形可以结果加重犯来处理。