Choice and conditioned reinforcement.

A potential weakness of one formulation of delay-reduction theory is its failure to include a term for rate of conditioned reinforcement, that is, the rate at which the terminal-link stimuli occur in concurrent-chains schedules. The present studies assessed whether or not rate of conditioned reinforcement has an independent effect upon choice. Pigeons responded on either modified concurrent-chains schedules or on comparable concurrent-tandem schedules. The initial link was shortened on only one of two concurrent-chains schedules and on only one of two corresponding concurrent-tandem schedules. This manipulation increased rate of conditioned reinforcement sharply in the chain but not in the tandem schedule. According to a formulation of delay-reduction theory, when the outcomes chosen (the terminal links) are equal, as in Experiment 1, choice should depend only on rate of primary reinforcement; thus, choice should be equivalent for the tandem and chain schedules despite a large difference in rate of conditioned reinforcement. When the outcomes chosen are unequal, however, as in Experiment 2, choice should depend upon both rate of primary reinforcement and relative signaled delay reduction; thus, larger preferences should occur in the chain than in the tandem schedules. These predictions were confirmed, suggesting that increasing the rate of conditioned reinforcement on concurrent-chains schedules may have no independent effect on choice.     

产权安排是社会道德的基础

作为社会经济生活中的一种根本制度安排和人们的一种基本权利,产权是社会道德的基础。一定的利益差别和产权界定,是道德产生的前提;社会产权制度的性质和变迁,规定着社会道德体系的特质和演变;社会产权安排的结构和状况,影响和制约着人们的道德行为选择和社会道德风尚。健全的产权安排有利于规范和约束人们的行为选择,安定人们的生活心态,创造积极的道德环境和条件,从而优化人们的道德行为选择,促进良好社会道德秩序的形成。     

Evaluating preschool children's preferences for motivational systems during instruction

Preschool teachers rely on several strategies for motivating children to participate in learning activities. In the current study, we evaluated the effectiveness of and preference for three teaching contexts in which embedded, sequential, or no programmed reinforcement was arranged. The embedded context included highly preferred teaching materials, the sequential context included highly preferred edible items for correct responding, and a control context included neither. In addition, an exclusively play-oriented activity was included as a fourth option to determine if one of the direct teaching contexts could compete with a relatively unstructured and exclusively child-led activity. All participants preferred the sequential context (use of high-quality consequences) over the embedded context (use of high-quality teaching materials), 2 of the 4 participants preferred some motivational system to none at all, and the play area was selected over all variants of the instructional contexts during the majority of trials. We found either no or small differences in correct responding in the different instructional contexts; however, rates of undesirable behavior were highest in the least preferred interaction area for 3 of the 4 participants. Implications for the design of effective and preferred teaching environments for young children are discussed.     

刺激放置朝向对返回抑制的影响:一项ERPs研究

返回抑制(inhibition of return, IOR)是指个体对出现在先前提示位置上的刺激反应更慢的现象。尽管大量ERPs研究发现呈现在线索化和非线索化位置上的靶刺激诱发的ERPs在250-300ms处存在一个稳定的差异(Nd250),但这一差异的方向却并不一致。本研究采用事件相关电位技术(Event-related Potentials, ERPs),结合经典的线索-靶子范式,考察刺激放置的朝向是否会影响到IOR中Nd250效应的极性。结果显示虽然刺激放置朝向并未有影响到Nd250的极性,却对早期P1成分的线索化效应的地形图分布有着显著的影响。这表明1）过往ERPs研究中的Nd250效应极性的不一致并非源于刺激放置朝向的作用;2）刺激的放置朝向会导致早期线索化效应(P1)在地形分布上出现差异。     

英国“代孕”合法化二十年历史回顾

在英国,代孕人工生殖是合法的医疗手段。《布雷热报告》等调查报告对英国代孕立法产生了深远影响。为实现生殖自由、子女利益和社会秩序的平衡,英国拟制定一部专门的《代孕法》。     

EVALUATION OF CLIENT PREFERENCE FOR FUNCTION-BASED TREATMENT PACKAGES

Functional communication training (FCT) and noncontingent reinforcement (NCR) are commonly prescribed treatments that are based on the results of a functional analysis. Both treatments involve delivery of the reinforcer that is responsible for the maintenance of destructive behavior. One major difference between the two treatment procedures is that client responding determines reinforcement delivery with FCT (e.g., reinforcement of communication is delivered on a fixed-ratio 1 schedule) but not with NCR (e.g., reinforcement is delivered on a fixed-time 30-s schedule). In the current investigation, FCT and NCR were equally effective in reducing 2 participants' destructive behavior that was sensitive to attention as reinforcement. After the treatment analysis, the participants' relative preference for each treatment was evaluated using a modified concurrent-chains procedure. Both participants demonstrated a preference for the FCT procedure. The results are discussed in terms of treatment efficacy and preference for control over when reinforcement is delivered. In addition, a method is demonstrated in which clients with developmental disabilities can participate in selecting treatments that are designed to reduce their destructive behavior.     

Uncertainty reduction, conditioned reinforcement, and observing

In a concurrent-chains procedure, pigeons chose between equivalent mixed and multiple fixed-interval schedules of reinforcement. In the first experiment, preference for the multiple schedule was higher when the probability of the shorter fixed interval was less than .50 than for complementary points, an outcome consistent with the delay-reduction hypothesis of conditioned reinforcement and observing, but inconsistent with the uncertainty-reduction hypothesis which requires symmetrical preferences with a maximum when the two intervals are equiprobable. A second experiment assessed preference for equivalent mixed and multiple schedules when each choice outcome resulted in two reinforcements, one on the longer and one on the shorter fixed interval. The order of the two fixed intervals was determined probabilistically. Pigeons again preferred multiple to mixed schedules, although multiple-schedule preference did not vary systematically with the likelihood of the shorter fixed interval occurring first. The results from these choice procedures are consistent with those from the observing-response literature in suggesting that the strength of a stimulus cannot be well described as a function of the degree of uncertainty reduction the stimulus provides about reinforcement.     

An evaluation of the value of choice with preschool children

The current study examined the reinforcing effects of choosing among alternatives in a four-part evaluation. In the first study, initial-link responses in a concurrent-chains arrangement resulted in access to terminal links in which the completion of an academic task resulted in (a) the choice of a reinforcer (choice), (b) the delivery of an identical reinforcer (no choice), or (c) no material reinforcer (control). Three patterns of responding emerged: persistent preference for choice (3 participants); initial preference for choice, which did not persist (2 participants); and preference for no choice (1 participant). Additional evaluations determined if preference for choice could be enhanced (Study 2) or established (Study 3) by including more stimuli from which to choose. Choice-link selections systematically increased for all participants when more items were available from which to choose. Study 4 identified the precise value of the opportunity to choose by progressively increasing the response requirement during the choice terminal links for 3 children and determining the point at which these children stopped selecting the choice link. All children continued to select the choice link even when the work required in the choice link was much greater than that arranged in the no-choice link.     

The effectiveness of and preschoolers' preferences for variations of multiple-schedule arrangements

Multiple schedules of reinforcement have been used to teach children to recruit attention only when it is available, thereby minimizing disruptive requesting during instructional activities. This procedure involves alternating periods of continuous reinforcement (CRF) with periods of extinction and correlating each period with a distinct and continuous discriminative stimulus. The present study evaluated the effectiveness of and children's preferences for multiple schedules in which (a) two different stimuli, one correlated with reinforcement (S+) and another correlated with extinction (S-), were presented; (b) only an S+ was presented (i.e., no stimulus was correlated with extinction), and (c) neither an S+ nor an S- was presented (i.e., a mixed schedule). S+/S- and S+ arrangements were similarly effective for 7 children, but 3 preferred the S+/S- condition and 4 preferred the S+ condition. Correlational analyses suggested that children who responded more effectively given the S- (discrimination indexes were relatively high) preferred the S+/S- condition, whereas children who responded less effectively given the S- preferred the S+ condition. The implications of these findings for arranging multiple schedules for social responses are discussed.     

Choice and delay of reinforcement: Effects of terminal-link stimulus and response conditions

In two experiments, pigeons were exposed to concurrent-chains schedules in which a single initial-link variable-interval schedule led to access to terminal links composed of fixed-interval or fixed-delay schedules. In Experiment 1, an 8-s (or 16-s) delay to reinforcement was associated with the standard key, while reinforcer delay values associated with the experimental key were varied from 4 to 32 s. The results of Experiment 1 showed undermatching of response ratios to delay ratios with terminal-link fixed-delay schedules, whereas in some pigeons matching or overmatching was evident with the fixed-interval schedules. In Experiment 2, one pair of reinforcer delay values, either 8 versus 16 s or 16 versus 32 s, was used. In the first condition of Experiment 2, different delays were associated with different keylight stimuli (cued condition). In the second condition, different terminal-link delays were associated with the same stimulus, either a blackout (uncued-blackout condition) or a white key (uncued-white condition). To examine the role of responses emitted during delays, the keys were retracted during a delay (key-absent condition) in the third condition and responses were required by a fixed-interval schedule in the fourth condition. Experiment 2 demonstrated that the choice proportions for the shorter delay were more extreme in the cued condition than in the uncued-blackout condition, and that the response requirement imposed by the fixed-interval schedules did not affect choice of the shorter delay, nor did the key-absent and key-present conditions. These results indicate that the keylight-stimulus conditions affected preference for the shorter of two delays and that the findings obtained in Experiment 1 depended mainly on the keylight-stimulus conditions of the terminal links (i.e., the conditioned reinforcing value of the terminal-link stimuli).