Stimulus devaluation and extinction of chain schedule performance

Pigeons were trained on a two-component multiple schedule in which each separate component consisted of a three-link chain schedule. After initial baseline training, the stimuli correlated with the terminal links of each chain were presented in a successive discrimination, with one stimulus continuing to be associated with reinforcement while responses to the alternative stimulus were extinguished. Subjects were then returned to the original chain schedule, but with extinction in effect in both components of the multiple schedule. In two separate experiments, extinction of initial-link responding was not affected by which terminal link had been extinguished during the separate discrimination training, indicating that devaluation of the terminal link was not transmitted directly to the initial link of the chain. There was also no effect of the devaluation procedure during the first session of testing on responding in the middle link of the chain, but an effect did develop with continued extinction of the entire chain when the terminal components were presented during extinction. When the terminal components were omitted, however, the latter effect did not occur. Also, when the terminal link was omitted, extinction occurred more rapidly in the middle component than in the initial component, indicating a backward pattern of extinction.     

Stimulus functions within a fixed-interval clock schedule: Reinforcement,punishment, and discriminative stimulus control

Pigeons received food for responding on a fixed-interval 32-sec schedule divided into three equal parts, each correlated with a distinctive, response-independent, visual stimulus. Response rate was very low during the first two thirds of the interval but high during the terminal third. When a response-dependent brief stimulus correlated with the terminal third was arranged for each response in the presence of the stimuli correlated with the first two thirds, response rate was enhanced, especially in the middle third. However, response rate was suppressed when each response in the presence of the stimulus correlated with the final third produced a brief stimulus correlated with the initial third. A similar suppressive effect occurred when each response produced a brief stimulus correlated with the middle third. Response suppression decreased over successive response-dependent brief-initial-stimulus manipulations. The results were interpreted in terms of reinforcement, punishment, and discriminative stimulus control by visual stimuli correlated with parts of a fixed-interval schedule.     

Perceptual discriminability and communication performance in preschool children.

The ability of preschool children to discriminate perceptually among novel forms frequently employed in referential communication tasks is examined. Results suggest that preschool children who are able to discriminate among the forms nevertheless perform poorly on a referential communication task involving these same forms. Asking children to provide names for the forms enhanced their discrimination performance but not their communication performance.     

Perceived contingency of reinforcements,helplessness, locus of control,and academic performance

To determine the relationships among perceived contigency of teacher-administered reinforcements, locus of control, teacher ratings of children's helplessness-competence, and academic achievement, 86 sixth graders (43 girls and 43 boys) were studied. In general, children's internality of locus of control and their perceptions that teachers administer rewards contingently were predictive of good academic achievement and teacher ratings of the children as competent as opposed to helpless. Perceptions of the contingency of teacher-administered punishments were unrelated to academic achievement or teacher ratings. For boys, locus of control and perceived contingency of teacher-administered rewards were significantly related, while for girls they were unrelated. Results are related to prior research linking perceived contingency of reinforcements, locus of control, and academic achievement.     

Sustained attention: Stimulus control determined by schedule of cue production interacting with cue duration

In a study of sustained attention (“vigilance”), pigeons performed a conditional discrimination in a 3-key operant chamber. Pecking a white center key initiated a 0.2- or 2.0-sec cue (a red or green disk). The side keys then displayed white disks, and a peck on the right or left key was reinforced depending on whether the preceding cue was red or green. Pecks on the white center key initiated the cue according to one of two schedules of cue production (FR 1 or VI 7.5 sec). Control of side key choices by 0.2-sec cues was disturbed by transition from FR 1 to VI 7.5, and recovered after the schedule of cue production changed from VI 7.5 back to FR 1. Control of choices by 2.0-sec cues was not affected by changing schedules of cue production. Rates of pecking the cue were higher than rates of cue-producing responses.     

Perceived contingency of teacher administered reinforcements and academic performance of boys

To determine the relationships among perceived contingency of teacher administered reinforcements, locus of control, and academic achievement, 49 sixth-grade boys were studied. In general, subjects who perceived their teachers as contingently punitive to boys were internal in locus of control and performed well on measures of academic achievement. An internal locus of control was also predictive of academic achievement. Perceived contingency of teacher rewards was not related to locus of control or academic achievement. These results were discussed as supporting the identity of learned helplessness and locus of control and the Seligman, Maier, and Solomon (1971) theory of learned helplessness.     

Stimulus spacing, attention, and dimensional contrast

We examine some implications of an attentional model designed to explain dimensional contrast. Pigeons were trained to discriminate rectangular forms under conditions that produced positive dimensional contrast. In two experiments, the spacing of training stimuli was manipulated in ways that should have changed the allocation of attention. Experiment 1 compared the effect of an increased spacing between negative and positive stimuli with the effect of a decreased overall range of positive stimuli. Both manipulations increased the quality of discrimination performance. Experiment 2 demonstrated that dimensional contrast continued to occur under conditions that minimized the difficulty of the task. Results from these experiments were consistent with quantitative predictions of the attentional model concerning the interaction of discriminability factors and factors related to the allocation of attentional resources.     

环境保护与经济激励

人类生存环境的污染问题日益严重,已经威胁到人类的生存.试图通过对环境保护的经济激励机制进行分析,以期找到减少污染、保护环境的方法和措施.经济激励机制是通过提高逃避控制成本,使生产者能够自行选择污染量,找到使控制污染成本最小的策略,从而使生产者为社会提供最优的污染控制水平.     

Discrimination blocking: Acquisition versus performance deficits in human contingency learning

We compared acquisition and performance accounts of human contingency learning. After solving a discrimination in Phase 1, in which Cue A predicted the occurrence of the outcome and Cue B predicted its nonoccurrence (A+/B−), a new discrimination (X+/Y−) was superimposed in Phase 2 (AX+/BY−). The participants were finally trained in Phase 3 with the added discrimination, which either maintained the same contingencies as those in Phase 2 (X+/Y−; Experiment 1) or reversed the contingencies (X−/Y+; Experiment 2). According to competitive-learning theories (e.g., Rescorla & Wagner, 1972), there should be no learning of the added discrimination in Phase 2, so that no advantage or disadvantage for this discrimination should be observed in Phase 3. In contrast, performance theories, such as the comparator hypothesis (Miller & Matzel, 1988), contend that learning of the added discrimination in Phase 2 should proceed normally; so, in Phase 3, an advantage for the added discrimination should be observed in Experiment 1, but a disadvantage should be observed in Experiment 2. Our participants learned about the added discrimination and generally showed the effects predicted by the comparator hypothesis.     

Conservation,matching, and the variable-interval schedule

The conservation model was generalized to the variable-interval schedule by incorporating the concept of unscheduled instrumental responses, those which occur in the time before the next setup is due. Thirsty rats responded in constant-duration sessions on two 7-sec schedules that required one leverpress for 25 and 50 licks at a water tube and on a 14-sec 25-lick schedule. In accordance with the model, total licks decreased linearly as total presses increased, and the schedules facilitated leverpressing and suppressed licking relative to paired baseline levels of responding. While the matching model also gave a satisfactory fit to instrumental responding under the schedules, its two constants, representing asymptotic rate of responding and extraneous reinforcement, had anomalous values which led the model to predict that response rate would decrease as the rate of reinforcement increased, directly opposing its prediction for the constant-consumption experiments of its previous tests.     

Prediction of concurrent keypeck treadle-press responding from simple schedule performance

Four pigeons pecked keys and pressed treadles for food reinforcers delivered by several variable-interval schedules of reinforcement. Then the subjects responded on several concurrent schedules. Keypecking produced reinforcers in one component, and treadle-pressing produced reinforcers in the other. The changeover delay, which prevented reinforcement after all switches from one response to the other, was 0, 5, or 20 sec long. An equation proposed by Kerrnstein (1970) described the rates of treadle-pressing and keypecking emitted during the variable-interval schedules. The k parameter of this equation was larger for keypecking than for treadle-pressing. The R₀ parameters were not systematically different for the two responses. The rates of keypecking and treadle-pressing emitted during the components of the concurrent schedules correlated with, but were not equal to, the rates of responding predicted by Herrnstein’s equation and the subject’s simple schedule responding. The ratios of the rates of responding emitted during, and the ratios of the time spent responding on, the components of the concurrent schedules conformed to an equation proposed by Baum (1974), but not to Herrnstein’s equation.     

Effects of discriminability, probability of reinforcement, and handling cost on visual search and prey choice

Pigeons searched for two targets that varied in similarity to items in the background. The targets, simulating “prey,” were small alphabetic characters presented on computer monitors among distractor characters. In the first experiment, the probability of reinforcement for pecking at the targets was manipulated. In the second experiment, the response requirement for one of the targets was varied. Changing the probability of reinforcement led to more efficient search and increased choice for the more reinforced item. This effect carried over to subsequent equal reinforcement baseline conditions. Increasing the response requirement for one item increased response time for that item and reduced choice of the item. This effect did not carry over to a subsequent baseline condition. The results suggested that a high probability of reinforcement resulted in improved detection of the item, perhaps through perceptual learning, and increased the incentive that motivated response to the item, but that high response requirement resulted only in an incentive shift.     

Biological significance attenuates overshadowing, relative validity, and degraded contingency effects

Miller and Matute (1996) showed that blocking is attenuated when the blocked conditioned stimulus (CS) is “biologically significant” (i.e., when the CS has the potential to elicit vigorous responding of any kind). To the extent that blocking is representative of cue competition, this finding suggests that biological significance protects CSs against cue competition effects in general. In the present experiments, we tested this possibility by examining the influence of biological significance of CSs on other examples of cue competition, namely, overshadowing, the relative stimulus validity effect, and the degraded contingency effect in rats. In Experiment 1, we found that intense auditory stimuli induced transient unconditioned lick suppression, thereby indicating that intense sounds were of high inherent biological significance. In Experiment 2A, we found that cues with high inherent biological significance were protected from overshadowing. In Experiment 2B, this finding was extended to cues with high acquired biological significance, which was obtained through prior pairings with a reinforcer of the valence opposite to that used in the overshadowing treatment. In Experiments 3 and 4, we found that cues with high inherent biological significance attenuated the relative validity effect and the degraded contingency effect, respectively. These results lend support to the view that biological significance (inherent and acquired) protects stimuli from cue competition effects, a finding that is problematic for many contemporary theories of learning.     

Decision type,structure, and process evaluation: A contingency model

Governance proposals for higher education in the United States are often promulgated on the basis of some utopian goal or on the assumption that a given proposal is the panacea for multifaceted problems or that it is equally applicable to diverse institutional settings. This paper, rather than promulgating a single proposal, takes a more analytic approach and develops a contingency model for identifying appropriate decision-making structures. First, emergent conditions in American higher education's external environment, in the internal social environment of its colleges and universities, and in the development of higher education management systems are analyzed to establish some long-range criteria for evaluating decision-making effectiveness. Second, a typology of institutional decisions categorized as policy, managerial, and operating decisions is presented. An analysis of the nature and content of each major type of decision suggests divergent patterns of formal and informal decision-making structures and patterns, and differing content and functions for the supporting management information technology which might be appropriate to each of the decision types or categories. Finally, the analysis relates the contingency notions of decision structure and type to the criteria for evaluating the decision-making process and suggests how they are compatible or might be modified to be more compatible. The model is a general conceptual one which the author suggests can be used on either an institution-wide basis or with particular subunits of a college or university.

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Types de decision, structures et evaluation des processus: un modele de contingence

Résumé Les projets officiels pour l'enseignement supérieur sont souvent formulés aux Etats-Unis par référence à un objectif idéal ou en supposant qu'un projet déterminé est susceptible de représenter la solution universelle de problèmes multidimensionnels et qu'il est également réalisable dans les différents contextes institutionnels. L'article ne vise pas à présenter un projet particulier; il se place au point de vue analytique et présente un modèle à éventualités multiples capable de déterminer les structures les plus appropriées à la prise de décision. En premier lieu, les caractéristiques nouvelles du milieu social dans lequel fonctionne aux Etats-Unis l'enseignement supérieur, les caractéristiques du milieu interne constitué par les collèges et les universités et les caractéristiques des systèmes de gestion pour l'Université sont soumises à l'examen afin de déterminer une large gamme de critères capables de s'appliquer à l'évaluation de l'efficacité des décisions. En second lieu, on présente une typologie des décisions institutionnelles dont les catégories sont celles de la détermination d'une politique, de la gestion et de l'application. L'analyse de la nature et du contenu de chacun des principaux types de décisions conduit à concevoir des structures et des formes différentes pour les prises de décision, tant explicites que diffuses, ainsi que des caractéristiques et des fonctions différentes pour la technologie de l'information sur laquelle repose la gestion, cela par référence aux différentes catégories de décision. En dernier lieu, l'analyse met en relations les notions variables de structure et de type de décision avec les critères retenus pour évaluer le processus de la prise de décision et examine jusqu'à quel point ils sont compatibles ou pourraient être modifiés afin de devenir plus compatibles. Le modèle présenté est un modèle théorique très général dont l'auteur suggère qu'il pourrait être utilisé tant pour une institution de large envergure que pour les sous-ensembles d'un collège ou d'une université.

     

The effects of reinforcement frequency on performance in a multiple fixed-ratio schedule

A barpress analog to the double-alley runway was sought by varying percentage reward in the first of two consecutive FR 18s. Groups of six rats each were given 0% 50%. or 100% reinforcement upon completion of the first FR 18: after a 5-sec midtnal imterval, the second FR 18 was administered on a separate lever and all groups received CRF reward upon its completion. Group 50 Ss performed faster after nonreward than after reward. Group 50 Ss performed faster after nonreward than did 0% Ss. A measure of midtnal behavior revealed a difference between groups in orienting to the bars. When all groups were shifted to a 50% first component schedule (Phase II), there were no statistically reliable effects of prior reinforcement history on rewarded or nonrewarded responding. The Phase 1 results were taken to demonstrate a frustration effect similar to that of the double alley     

Stimulus variation and dimensional contrast

In two experiments, a maintained generalization procedure was employed to examine stimulus control of pigeons’ responses to a visual wavelength continuum. For both experiments, pigeons’ responses were periodically reinforced during wavelength values from one end of a continuum, while responses during other stimulus values were extinguished. In Experiment 1, the set of positive stimulus values remained constant, while the spacing of the set of negative stimuli varied. In Experiment 2, the set of negative stimulus values remained constant, while the spacing of positive stimuli varied. Positive dimensional contrast effects were obtained in both experiments. In general, the results indicated that variation in the spacing of negative stimuli had little effect on positive dimensional contrast. However, variation in the spacing of positive stimuli produced changes in the peak of the dimensional contrast gradient, without apparent change in the magnitude of the effect.     

Flavor evaluative conditioning and contingency awareness

The relationship between flavor evaluative conditioning and contingency awareness was examined in two experiments using flavored drinks. In Experiment 1, one flavor was always paired with sugar and the other with bitter tween (polysorbate20) during conditioning. In a subsequent test phase, participants tasted the two flavors, and their evaluative ratings indicated an overall preference for the sugar-paired flavor. Moreover, participants were generally able to report which flavor had been paired with sugar and which with tween. This finding was replicated and confirmed in Experiment 2A. Furthermore, in both experiments, evaluative conditioning was seen only in those participants who were aware of the contingencies. Experiment 2B demonstrated that evaluative conditioning does not occur to colors, although participants are contingency aware. The differences between the present findings and prior studies, in which apparently unaware flavor conditioning has been found, are discussed.