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PubMed1993

Molar versus local reinforcement probability as determinants of stimulus value.

During one component of a multiple schedule, pigeons were trained on a discrete-trial concurrent variable-interval variable-interval schedule in which one alternative had a high scheduled rate of reinforcement and the other a low scheduled rate of reinforcement. When the choice proportion between the alternatives matched their respective relative reinforcement frequencies, the obtained probabilities of reinforcement (reinforcer per peck) were approximately equal. In alternate components of the multiple schedule, a single response alternative was presented with an intermediate scheduled rate of reinforcement. During probe trials, each alternative of the concurrent schedule was paired with the constant alternative. The stimulus correlated with the high reinforcement rate was preferred over that with the intermediate rate, whereas the stimulus correlated with the intermediate rate of reinforcement was preferred over that correlated with the low rate of reinforcement. Preference on probe tests was thus determined by the scheduled rate of reinforcement. Other subjects were presented all three alternatives individually, but with a distribution of trial frequency and reinforcement probability similar to that produced by the choice patterns of the original subjects. Here, preferences on probe tests were determined by the obtained probabilities of reinforcement. Comparison of the two sets of results indicates that the availability of a choice alternative, even when not responded to, affects the preference for that alternative. The results imply that models of choice that invoke only obtained probability of reinforcement as the controlling variable (e.g., melioration) are inadequate.

Animals↗
PubMed1992

How pigeons estimate rates of prey encounter.

Pigeons were trained on operant schedules simulating successive encounters with prey items. When items were encountered on variable-interval schedules, birds were more likely to accept a poor item (long delay to food) the longer they had just searched, as if they were averaging prey density over a short memory window (Experiment 1). Responding as if the immediate future would be like the immediate past was reversed when a short search predicted a long search next time (Experiment 2). Experience with different degrees of environmental predictability appeared to change the length of the memory window (Experiment 3). The results may reflect linear waiting (Higa, Wynne, & Staddon, 1991), but they differ in some respects. The findings have implications for possible mechanisms of adjusting behavior to current reinforcement conditions.

Analysis of Variance↗
PubMed2002

Development and evaluation of an interactive Web-based breast imaging game for medical students.

RATIONALE AND OBJECTIVES: The purpose of this study was to develop and evaluate by student survey an interactive computer tool for teaching breast imaging to 4th-year medical students. MATERIALS AND METHODS: An interactive computer game was designed for competitive play between two students or between one student and one of two cyber players. Content was determined from a survey of faculty members in breast imaging, and the survey results were grouped into 10 learning objectives. Pre-existing knowledge of these objectives in 16 4th-year medical students was tested by a quiz. On the basis of the learning objectives, case scenarios and questions were incorporated into the game, which was programmed in JavaScript and available on a Web site. Preliminary and final versions of the game were used for teaching 55 4th-year medical students. A subgroup of 42 students received an informational handout. Student surveys were performed. RESULTS: Mean quiz score for pre-existing knowledge of the learning objectives was 45% (range, 13%-67%). Survey results showed that images contributed to educational value (92%), the Web site was more interesting to students than the handout (93.6%), and the Web site provided additional reinforcement of learning beyond that of the handout or lecture (88.8%). Students liked the Web site accessibility (96%), and more than 70% agreed the Web site was also appropriate for other medical specialties. An Internet search identified no other Web-based computer games for medical students. CONCLUSION: Students surveyed found the Web site to be worthwhile, convenient, and applicable to other specialties.

Breast↗
PubMed1990

Choice behavior in transition: development of preference for the higher probability of reinforcement.

Ten acquisition curves were obtained from each of 4 pigeons in a two-choice discrete-trial procedure. In each of these 10 conditions, the two response keys initially had equal probabilities of reinforcement, and subjects' choice responses were about equally divided between the two keys. Then the reinforcement probabilities were changed so that one key had a higher probability of reinforcement (the left key in half of the conditions and the right key in the other half), and in nearly every case the subjects developed a preference for this key. The rate of acquisition of preference for this key was faster when the ratio of the two reinforcement probabilities was higher. For instance, acquisition of preference was faster in conditions with reinforcement probabilities of .12 and .02 than in conditions with reinforcement probabilities of .40 and .30, even though the pairs of probabilities differed by .10 in both cases. These results were used to evaluate the predictions of some theories of transitional behavior in choice situations. A trial-by-trial analysis of individual responses and reinforcers suggested that reinforcement had both short-term and long-term effects on choice. The short-term effect was an increased probability of returning to the same key on the one or two trials following a reinforcer. The long-term effect was a gradual increase in the proportion of responses on the key with the higher probability of reinforcement, an increase that usually continued for several hundred trials.

Animals↗
PubMed1984

Uncontrollable shock proactively increases sensitivity to response-reinforcer independence in rats.

Learned helplessness theory predicts that animals exposed to inescapable shock acquire an expectancy of response-reinforcer independence, which proactively interferes with learning of response-reinforcer dependence. The theory also predicts that this expectancy can increase sensitivity to subsequent instances of response-reinforcer independence. These experiments test the latter prediction in a paradigm that minimizes the confounding effects of shock-induced activity deficits. Rats were trained to respond for food, then given either escapable, inescapable, or no shock. Subsequently, they received two sessions of response-contingent food followed by sessions of noncontingent food deliveries. During this phase, inescapably shocked animals decreased responding faster than did controls. Experiment 2 replicated this finding with a different schedule of food delivery and a procedure that more directly minimized the possibility that the outcome is due to either direct or indirect shock-induced activity changes. These results support the prediction that uncontrollable aversive events can increase an animal's sensitivity to noncontingent response-reinforcer relationships.

Animals↗
PubMed2005

Behavioral and associative effects of differential outcomes in discrimination learning.

The role of the reinforcer in instrumental discriminations has often been viewed as that of facilitating associative learning between a reinforced response and the discriminative stimulus that occasions it. The differential-outcome paradigm introduced by Trapold (1970), however, has provided compelling evidence that reinforcers are also part of what is learned in discrimination tasks. Specifically, when the availability of different reinforcing outcomes is signaled by different discriminative stimuli, the conditioned anticipation of those outcomes can provide another source of stimulus control over responding. This article reviews how such control develops and how it can be revealed, its impact on behavior, and different possible mechanisms that could mediate the behavioral effects. The main conclusion is that differential-outcome effects are almost entirely explicable in terms of the cue properties of outcome expectancies-namely, that conditioned expectancies acquire discriminative control just like any other discriminative or conditional stimulus in instrumental learning.

Animals↗
PubMed2004

Simulation and clinical practice: strengthening the relationship.

INTRODUCTION: This discussion paper argues for a creative synthesis between simulation and clinical practice, where an iterative process of continual interaction ensures that skills are learned and reinforced within the context of everyday professional life. BACKGROUND: Evidence is mounting that long-established approaches to surgical training are no longer acceptable in the current ethical and professional climate. This paper considers alternatives to the traditional approach of 'learning by doing' in a clinical context, focusing on recent developments in the technology of simulation and virtual reality. Clinical expertise is a complex phenomenon and no single theory can account for its acquisition. After a brief contextualising overview, Vygotsky's 'zone of proximal development' is proposed as a conceptual framework for task-based surgical learning that takes place within skills laboratories. The discussion is located within a wider context of educational theory, drawing on current thinking about situated learning and apprenticeship. The notion of 'legitimate peripheral participation' in a complex professional environment places technical skill alongside a range of other competencies that are necessary to safe practice. CONCLUSIONS: Simulation offers a safe environment within which learners can repeatedly practise a range of clinical skills without endangering patients. Comprehensive simulated environments allow a move away from isolated tasks to more complex clinical situations, recreating many of the challenges of real life. Such simulations, however, can operate in isolation from their clinical context, ignoring the learning needs of individuals within a real health care environment. To realise its full potential as a learning aid, simulation must be used alongside clinical practice and linked closely with it.

Clinical Competence↗
PubMed1995

[Short intertrial interval as a phrasing cue in the serial pattern learning in rats].

Phrasing effect of short intertrial interval (ITI) on the serial pattern learning was investigated in a runway experiment. In acquisition, all 10 rats were given three repetitions of 14-7-3-1-0 subpattern daily over Days 1-80. For Group NP (non phrasing), all daily 15 trials were separated by a 15-min ITI. Group GP (good phrasing) and Group BP (bad phrasing) received the same procedure as Group NP except, instead of the 15-min ITI, a 15-s ITI was inserted between the 0 pellet and 14 pellets trial in the former, and a 15-s ITI was inserted between the 3 pellets and 1 pellet trial in the latter. Means of the last 4 days of acquisition as indicated by running speed showed that Group GP produced better anticipation of the 0 pellet trial than Group NP, and that Group BP produced the poorest anticipation. In Group BP, rats ran more slowly on the 1 pellet trial, that occurred after the 15-s ITI, than on the 0 pellet trial in each of the first and second subpatterns. These results suggest that a shorter ITI plays dual roles, as a phrasing cue and as a discriminative stimulus in the serial pattern learning as that does in reinforcement-nonreinforcement pattern learning.

Animals↗
PubMedDate not supplied

Increased regularity of activity of cortical neurons in learning due to disinhibitory effect of reinforcement.

This paper reviews the author's studies on neurophysiologic mechanisms of conditioned reflex learning. Electroencephalograms, evoked potentials, activity of neocortical and hippocampal neurons and the rabbits' behavior in the course of elaboration of defensive and inhibitory conditioned reflexes to light flashes have been recorded. Electric shock (ECS) applied to the paw served as reinforcement. The study demonstrated three types of reinforcement effect on the activity of cortical neurons: activating, disinhibitory, and inhibitory. EEG activation due to reinforcement is accompanied by a change in phasic cortical neuronal activity from chaotic or irregular, typical of rest or inhibition, to regular tonic discharges (in neocortex and hippocampus) and group discharges in the stress rhythm, 5-7 Hz in the hippocampus. Following a number of conditioning trials, the effect of reinforcement is simulated by the effect of a conditioned stimulus. With EEG activation and increased regularity in impulses, facilitation of motor reactions is observed.

Animals↗
PubMed1993

A neuron-like network with the ability to learn coordinated movement patterns.

A model calculation is presented simulating the coordinated interaction between the walking legs of a multi-legged animal. The neural network consists of separate modules with oscillatory capabilities. It has the ability to adjust the necessary parameters for producing a coordinated interaction between the modules in a self-organizing fashion. Some sort of reinforcement comparison learning is used to train the network. It starts oscillations in a completely uncoupled state. After about 100 learning steps, the generation of a stable alternating pattern is usually terminated. Then, the network is able to maintain synchronization, even when disturbances are applied to single agents or to the network as a whole.

Animals↗
PubMed1987

Early experience and reinforcer quality in delayed flavour-food learning in the rat.

The ability of hungry rats to associate flavours with the consequences of ingesting glucose solutions was studied in three experiments. Experiment 1 used a procedure in which on some days one flavour, e.g. cinnamon, was presented and followed after 20 min by 20% glucose, while on other days a second flavour, e.g. wintergreen, was presented, but not followed by any event. During this training, subjects who received quinine-tainted glucose increased their consumption of the predictive flavour relative to groups given no quinine, but quinine tainting did not affect conditioned preference for the predictive flavour in choice tests. With the aim of discovering whether prior experience of a variety of foods improves ability to learn new flavour-calorie associations, Experiment 2 and used a similar procedure to compare subjects raised on a varied diet ("supermarket" rats) with controls previously given only chow. Contrary to expectation, the supermarket rats showed some impairment both on this delay task and, in Experiment 3, on one using a "mixtures" procedure. This involved presenting a mixture of one cue flavour with glucose-quinine on some days and a mixture of a second cue with an equally palatable saccharin solution on other days. Acquisition was particularly rapid in control subjects, reaching asymptote after only two flavour-glucose pairings. It was concluded that neither a decrease in palatability, as in Experiment 1, nor prior experience with a range of foods, as in Experiments 2 and 3, improve a rat's ability to associate a new flavour with calories.

Analysis of Variance↗
PubMed1979

Brain stimulation and reward: "pleasure centers" after twenty-five years.

"Self-stimulation" is a phenomenon whereby an animal (including a human being) will repeatedly stimulate its brain electrically, sometimes to the point of exhaustion. This phenomenon is robust and readily reproducible in many areas of the brain, particularly in nuclei and fiber tracts known to be monoaminergic, and it has been the basis for the study of reinforcement and learning mechanisms in the brain. The last 25 years of work on intracranial self-stimulation is reviewed with an emphasis on mechanisms, primarily catecholaminergic. Implications for learning and pain mechanisms are discussed.

Acetylcholine↗
PubMedDate not supplied

[The role of motivation in the performance of a conditioned switching-over of the maze habit in ants Myrmica rubra after a change in the quality of the food reinforcement].

Active foragers Myrmica rubra were trained in a maze under conditions of different levels of colony need in food with carbohydrate (sugar syrup) or protein (ants Lasius niger pupae) reinforcement. Acquisition of the maze habit was better under conditions of reinforcement with pupae, especially by its time indices. Ants were able to modify the acquired habit when the reinforcement quality was changed. It was shown that learning was possible only when the colony and after a change pupae for the syrup was "hungry". Under these conditions, after a change of the syrup for pupae or visa versa the previously acquired optimum habit was transferred. Several hours later, with satiation of the colony, food reactions learned with protein reinforcement switched-over to "stochastic" non-optimized behavior with the dominance of exploratory reactions. Thus, it was shown that higher social insects ants were capable for conditioned switching-over. Different forms of this phenomenon depended on the level of the colony need in food and, consequently, on the level of the social food motivation of foragers ants.

Animals↗
PubMed2005

Resistance to change of forgetting functions and response rates.

This experiment examined the effects of reinforcement probability on resistance to change of remembering and response rate. Pigeons responded on a two-component multiple schedule in which completion of a variable-interval 20-s schedule produced delayed matching-to-sample trials in both components. Each session included four delays (0.1 s, 2 s, 4 s, and 8 s) between sample termination and presentation of comparison stimuli in both components. The two components differed in the probability of reinforcement arranged for correct matches (i.e., rich, p = .9; lean, p = .1). Response rates during the variable-interval portion of the procedure were higher in the rich component during baseline and more resistant to the disruptive effects of intercomponent food and extinction. Forgetting functions were constructed by examining matching accuracy as a function of delay duration. Baseline accuracy was higher in the rich component than in the lean component as measured by differences in the gamma-intercept of the forgetting functions (i.e., initial discrimination), rather than from differences in the slope of the forgetting function (i.e., rate of forgetting). Intercomponent food increased the rate of forgetting relatively more in the lean component than in the rich component, but initial discrimination was not systematically affected. Extinction reduced initial discrimination relatively more in the lean component than in the rich component, but did not systematically affect rate of forgetting. These results are consistent with our previous data suggesting that, as for response rate, accuracy and resistance to change of discriminating are positively related to rate of reinforcement. These data also suggest that the disruptability of remembering depends on the conditions of reinforcement, but the way in which remembering is disrupted depends on the nature of the disruptor.

Animals↗
PubMed1989

A test of the response deprivation hypothesis in a multiple-response context.

Reinforcement contingencies defined by the response deprivation hypothesis were evaluated in two multiple-response contexts. In one context a high probability response was freely available, and in the other context a low probability response was freely available. In the presence of the low probability, freely available response, a consistent reinforcement effect was evident for all 3 moderately mentally retarded participants; however, in the presence of the high probability response, the reinforcement effect was attenuated. Results were qualitatively consistent with several recent mathematical descriptions of behavior emphasizing the importance of the context in which reinforcement contingencies are introduced.

Adolescent↗
PubMed2003

Learned material content and acquisition level modulate cerebral reactivation during posttraining rapid-eye-movements sleep.

We have previously shown that several brain areas are activated both during sequence learning at wake and during subsequent rapid-eye-movements (REM) sleep (Nat. Neurosci. 3 (2000) 831-836), suggesting that REM sleep participates in the reprocessing of recent memory traces in humans. However, the nature of the reprocessed information remains open. Here, we show that regional cerebral reactivation during posttraining REM sleep is not merely related to the acquisition of basic visuomotor skills during prior practice of the serial reaction time task, but rather to the implicit acquisition of the probabilistic rules that defined stimulus sequences. Moreover, functional connections between the reactivated cuneus and the striatum--the latter being critical for implicit sequence learning--are reinforced during REM sleep after practice on a probabilistic rather than on a random sequence of stimuli. Our results therefore support the hypothesis that REM sleep is deeply involved in the reprocessing and optimization of the high-order information contained in the material to be learned. In addition, we show that the level of acquisition of probabilistic rules attained prior to sleep is correlated to the increase in regional cerebral blood flow during subsequent REM sleep. This suggests that posttraining cerebral reactivation is modulated by the strength of the memory traces developed during the learning episode. Our data provide the first experimental evidence for a link between behavioral performance and cerebral reactivation during REM sleep.

Adult↗