On conditioned reinforcing effects of negative discriminative stimuli

Observing responses by pigeons were studied during sessions in which a food key and an observing key were available continuously. A variable-interval schedule and extinction alternated randomly on the food key. In one condition, food-key pecking during extinction decreased reinforcement frequency during the next variable-interval component, and in the other condition such pecking did not affect reinforcement frequency. Observing responses either changed both keylight colors from white to green (S+) or to red (S−) depending on the condition on the food key, or the observing responses never produced the S+ but produced the S− when extinction was in effect on the food key. Observing responses that produced only S− were maintained only when food-key pecking during extinction decreased reinforcement frequency in the subsequent variable-interval component. The red light conformed to conventional definitions of a negative discriminative stimulus, rendering results counter to previous findings that production of S− alone does not maintain observing. Rather than offering support for an informational account of conditioned reinforcement, the results are discussed in terms of a molar analysis to account for how stimuli acquire response-maintaining properties.     

Human observing: maintained by negative informative stimuli only if correlated with improvement in response efficiency.

Two experiments investigated the effect of observing responses that enabled college students to emit more efficient distributions of reinforced responses. In Experiment 1, the gains of response efficiency enabled by observing were minimized through use of identical low-effort response requirements in two alternating variable-interval schedules. These comprised a mixed schedule of reinforcement; they differed in the number of money-backed points per reinforcer. In each of three choices between two stimuli that varied in their correlation with the variable-interval schedules, the results showed that subjects preferred stimuli that were correlated with the larger average amount of reinforcement. This is consistent with a conditioned-reinforcement hypothesis. Negative informative stimuli--that is, stimuli correlated with the smaller of two rewards--did not maintain as much observing as stimuli that were uncorrelated with amount of reward. In Experiment 2, savings in effort made possible by producing S- were varied within subjects by alternately removing and reinstating the response-reinforcement contingency in a mixed variable-interval/extinction schedule of reinforcement. Preference for an uncorrelated stimulus compared to a negative informative stimulus (S-) decreased for each of six subjects, and usually reversed when observing permitted a more efficient temporal distribution of the responses required for reinforcement; in this case, the responses were pulls on a relatively high-effort plunger. When observing the S- could not improve response efficiency, subjects again chose the control stimulus. All of these results were inconsistent with the uncertainty-reduction hypothesis.     

Choice: A local analysis

Analyses of free-operant choice usually employ one of two general procedures: the simple concurrent procedure (i.e., a concurrent variable-interval variable-interval schedule) or the concurrent-chains procedure (i.e., concurrently available initial links, each leading to an exclusively available terminal link). Theories about choice usually focus on only one of the two procedures. For example, maximization theories, which assert that behavior is distributed between two alternatives in such a way that overall rate of reinforcement is maximized, have been applied only to the simple concurrent procedure. In the present paper, a form of the pairing hypothesis (according to which pairings between one stimulus and another affect the value of the first, and pairings between responses and reinforcers affect the value of the former) is developed in a way that allows it to make qualitative predictions with regard to choice in a variety of simple concurrent and concurrent-chains procedures. The predictions include matching on concurrent variable-interval variable-interval schedules, preference reversal in the self-control paradigm, and preference for tandem over chained terminal links.     

Resistance to change and relapse of observing

Four experiments examined relapse of extinguished observing behavior of pigeons using a two-component multiple schedule of observing-response procedures. In both components, unsignaled periods of variable-interval (VI) food reinforcement alternated with extinction and observing responses produced stimuli associated with the availability of the VI schedule (i.e., S+). The components differed in the rate of food arranged (Rich = VI 30 s; Lean = VI 120 s). In Experiment 1, following baseline training, extinction of observing involved removal of both food and S+ deliveries, and reinstatement was examined by presenting either response-independent food or S+ deliveries. In Experiment 2, extinction involved removal of only food deliveries while observing responses continued to produce S+. Reinstatement was examined by delivering food contingent upon the first two food-key responses occurring in the presence of the S+. Experiment 3 assessed ABA renewal of observing by extinguishing food-key and observing responses in the presence of one contextual stimulus (i.e., B) and then returning to the original training context (i.e., A) during continued extinction. Experiment 4 examined resurgence by introducing food reinforcement for an alternative response during extinction, and subsequently removing that alternative source of food. Across experiments, relative resistance to extinction and relapse of observing tended to be greater in the component previously associated with the higher rate of primary reinforcement. Relapse of observing or attending to stimuli associated with primary reinforcement appears to be impacted by frequency of primary reinforcement in a manner similar to responding maintained directly by primary reinforcement.     

Divided stimulus control: a replication and a quantitative model

Four pigeons were trained on a conditional discrimination. The conditional stimuli were compounds of pairs of stimuli from two different dimensions, fast versus slow cycles of red or green stimuli, and short- versus long-duration presentations of these cycles. Across conditions, the probability of reinforcers for correctly responding to each dimension was varied from 0 to 1. Discriminability, measured by log d, for stimuli on a dimension increased as the relative frequency of reinforcers for that dimension increased, replicating the results of Shahan and Podlesnik (2006). Two further conditions showed that discriminability between stimuli on each dimension was unaffected by whether the stimuli on the other dimension varied or were constant. Finally, maximal discriminability was unchanged in a redundant-relevant cues condition in which either of the stimuli comprising a compound signaled the same correct response. Davison and Nevin's (1999) model provided an excellent quantitative account of the effect of relative reinforcer frequency on discriminability, and thus of the way in which divided stimulus control is itself controlled by relative reinforcement.     

条件性的关联学习和消退过程的性别差异

采用事件相关电位技术和条件性关联学习模型相结合的方法, 考察在负性背景下男女性对一般事件的关联学习和消退是否存在差异。结果表明：在关联学习阶段, 男性较女性表现出P2潜伏期缩短和N2波幅增大, 而女性比男性表现出更大的P3波幅。在消退阶段, 女性较男性出现更小的P2波幅和更大的P3/LPP波幅。这说明女性可能慢于男性探索到条件刺激和非条件刺激之间的关联, 并且保持时间更久; 男性在相对早期对消退产生更大的反应, 女性则在相对晚期对消退投入更多的资源及努力。     

动物信号追踪和目标追踪行为及其神经机制

信号追踪和目标追踪的实质是条件刺激和非条件刺激结合诱导的条件性接近反应.条件刺激的预测作用和诱因作用是信号追踪和目标追踪的重要机制;伏隔核、中央杏仁核和前扣带回在信号追踪和目标追踪过程中具有重要作用;然而,大脑皮层和海马损伤对两者影响较小.DA功能降低可损害信号追踪获得和表达;而脑内DA含量增加可提高目标追踪.未来的研究中,应该规范条件刺激和非条件刺激的类型和设置方法,针对不同的研究目的个别地或同时地测量信号追踪和目标追踪.     

Establishing books as conditioned reinforcers for preschool children as a function of an observational intervention

We tested the effects of an observational intervention (Greer & Singer-Dudek, 2008) on establishing children's books as conditioned reinforcers using a delayed multiple baseline design. Three preschool students with mild language and developmental delays served as the participants. Prior to the intervention, books did not function as reinforcers for any of the participants. The observational intervention consisted of a situation in which the participant observed a confederate being presented with access to books contingent on correct responses and the participant received nothing for correct responses. After several sessions of this treatment, the previously neutral books acquired reinforcing properties for maintenance and acquisition responses for all three participants.     

Establishing praise as a conditioned reinforcer: Pairing with one versus multiple reinforcers

Praise and other forms of attention may not function as reinforcers for the behavior of children with autism. Previous research demonstrated that contingently pairing praise with reinforcers (response stimulus) can establish praise as a conditioned reinforcer. We evaluated a procedure for establishing praise as a generalized conditioned reinforcer (pair praise with four reinforcers) and compared it with a procedure to establish praise as a conditioned reinforcer (pair praise with one reinforcer). We compared the two conditions in a reversal design with “praise” and “no programmed consequence” conditions rapidly alternated after pairing phases. With three out of five participants with autism, responding in the “pair‐with‐four” condition showed higher levels of responding or more increasing trends compared with that in “pair‐with‐one” condition. We also replicated previous contingent pairing research with two participants in a multiple baseline across participants design. A limitation was the absence of manipulating motivating operations in assessing the efficacy of praise as a generalized conditioned reinforcer. Nevertheless, these data contribute to the research on establishing praise as a reinforcer, and we recommend directions for future research.