Biomedical subjects

William M Baum

Publications and source records attributed to William M Baum.

9 recordsLinked to original sources

PubMed2006

Do conditional reinforcers count?

Six pigeons were trained on a procedure in which seven components arranged different food-delivery ratios on concurrent variable-interval schedules each session. The components were unsignaled, lasted for 10 food deliveries, and occurred in random order with a 60-s blackout between components. The schedules were arranged using a switching-key procedure in which two responses on a center key changed the schedules and associated stimuli on two side keys. In Experiment 1, over five conditions, an increasing proportion of food deliveries accompanied by a magazine light was replaced with the presentation of the magazine light only. Local analyses of preference showed preference pulses toward the alternative that had just produced either a food-plus-magazine-light or magazine-light-only presentation, but pulses after food deliveries were always greater than those after magazine lights. Increasing proportions of magazine lights did not change the size of preference pulses after food or magazine-light presentations. Experiment 2 investigated the effects of correlations between food ratios and magazine-light ratios: In Condition 6, magazine-light ratios in components were inversely correlated (-1.0) with food ratios, and in Condition 7, magazine-light ratios were uncorrelated with food ratios. In Conditions 8 and 9, pecks also produced occasional 2.5-s flashes of a green keylight. In Condition 8, food and magazine-light ratios were correlated 1.0 whereas food and green-key ratios were correlated -1.0. In Condition 9, food and green-key ratios were correlated 1.0 whereas food and magazine-light ratios were correlated -1.0. Preference pulses toward alternatives after magazine lights and green keys depended on the correlation between these event ratios and the food ratios: If the ratios were correlated +1.0, positive preference pulses resulted; if the correlation was -1.0, preference pulses were negative. These results suggest that the Law of Effect has more to do with events signaling consequences than with strengthening responses.

Animals↗

PubMed2006

Fix and sample with rats in the dynamics of choice.

The generality of the molar view of behavior was extended to the study of choice with rats, showing the usefulness of studying order at various levels of extendedness. Rats' presses on two levers produced food according to concurrent variable-interval variable-interval schedules. Seven different reinforcer ratios were arranged within each session, without cues identifying them, and separated by blackouts. To alternate between levers, rats pressed on a third changeover lever. Choice changed rapidly with changes in component reinforcer ratio, and more presses occurred on the lever with the higher reinforcer rate. With continuing reinforcers, choice shifted progressively in the direction of the reinforced lever, but shifted more slowly with each new reinforcer. Sensitivity to reinforcer ratio, as estimated by the generalized matching law, reached an average of 0.9 and exceeded that documented in previous studies with pigeons. Visits to the more-reinforced lever preceded by a reinforcer from that lever increased in duration, while all visits to the less-reinforced lever decreased in duration. Thus, the rats' performances moved faster toward fix and sample than did pigeons' performances in previous studies. Analysis of the effects of sequences of reinforcer sources indicated that sequences of five to seven reinforcers might have sufficed for studying local effects of reinforcers with rats. This study supports the idea that reinforcer sequences control choice between reinforcers, pulses in preference, and visits following reinforcers.

Animals↗

PubMed2004

Molar and molecular views of choice.

The molar and molecular views of behavior are not different theories or levels of analysis; they are different paradigms. The molecular paradigm views behavior as composed of discrete units (responses) occurring at moments in time and strung together in chains to make up complex performances. The discrete pieces are held together as a result of association by contiguity. The molecular view has a long history both in early thought about reflexes and in associationism, and, although it was helpful to getting a science of behavior started, it has outlived its usefulness. The molar view stems from a conviction that behavior is continuous, as argued by John Dewey, Gestalt psychologists, Karl Lashley, and others. The molar paradigm views behavior as inherently extended in time and composed of activities that have integrated parts. In the molar paradigm, activities vary in their scale of organization--i.e., as to whether they are local or extended--and behavior may be controlled sometimes by short-term relations and sometimes by long-term relations. Applied to choice, the molar paradigm rests on two simple principles: (a) all behavior constitutes choice; and (b) all activities take time. Equivalence between choice and behavior occurs because every situation contains more than one alternative activity. The principle that behavior takes time refers not simply to any notion of response duration, but to the necessity that identifying one action or another requires a sample extended in time. The molecular paradigm's momentary responses are inferred from extended samples in retrospect. In this sense, momentary responses constitute abstractions, whereas extended activities constitute concrete particulars. Explanations conceived within the molecular paradigm invariably involve hypothetical constructs, because they require causes to be contiguous with responses. Explanations conceived within the molar paradigm retain direct contact with observable variables.

Animals↗

PubMed2004

Choice in a variable environment: visit patterns in the dynamics of choice.

Molar and molecular views of behavior imply different approaches to data analysis. The molecular view privileges moment-to-moment analyses, whereas the molar view supports analysis of more and less extended activities. In concurrent performance, the molar view supports study of both extended patterns of choice and more local patterns of visiting the choice alternatives. Analysis of the present data illustrated the usefulness of investigating order at various levels of extendedness. Seven different reinforcer ratios were presented within each session, without cues to identify them, and pigeons pecked at two response keys that delivered food on variable-interval schedules. Choice changed rapidly within components as reinforcers were delivered and, following each reinforcer, shifted toward the alternative that produced it. If several reinforcers were delivered consecutively by one alternative, choice favored that alternative, but shifted more slowly with each new reinforcer. A discontinuation of such a series of reinforcers by the delivery of a reinforcer by the other alternative resulted in a large shift of choice toward that alternative. These effects were illuminated by analysis of visits to the two alternatives. Changes in visit length occurred primarily in the first postreinforcer visit to the repeatedly reinforced alternative. All other visits tended to be brief and equal. Performance showed multiple signs of moving in the direction of a fix-and-sample pattern that characterized steady-state performance in earlier experiments with many sessions of maintaining each schedule pair. The analyses of extended and local patterns illustrate the flexibility of a molar view of behavior.

Animals↗

PubMed2003

Every reinforcer counts: reinforcer magnitude and local preference.

Six pigeons were trained on concurrent variable-interval schedules. Sessions consisted of seven components, each lasting 10 reinforcers, with the conditions of reinforcement differing between components. The component sequence was randomly selected without replacement. In Experiment 1, the concurrent-schedule reinforcer ratios in components were all equal to 1.0, but across components reinforcer-magnitude ratios varied from 1:7 through 7:1. Three different overall reinforcer rates were arranged across conditions. In Experiment 2, the reinforcer-rate ratios varied across components from 27:1 to 1:27, and the reinforcer-magnitude ratios for each alternative were changed across conditions from 1:7 to 7:1. The results of Experiment 1 replicated the results for changing reinforcer-rate ratios across components reported by Davison and Baum (2000, 2002): Sensitivity to reinforcer-magnitude ratios increased with increasing numbers of reinforcers in components. Sensitivity to magnitude ratio, however, fell short of sensitivity to reinforcer-rate ratio. The degree of carryover from component to component depended on the reinforcer rate. Larger reinforcers produced larger and longer postreinforcer preference pulses than did smaller reinforcers. Similar results were found in Experiment 2, except that sensitivity to reinforcer magnitude was considerably higher and was greater for magnitudes that differed more from one another. Visit durations following reinforcers measured either as number of responses emitted or time spent responding before a changeover were longer following larger than following smaller reinforcers, and were longer following sequences of same reinforcers than following other sequences. The results add to the growing body of research that informs model building at local levels.

Animals↗

PubMed2002

The Harvard Pigeon Lab under Herrnstein.

The history of the Harvard Pigeon Lab is a history of two periods of remarkable productivity, the first under Skinner's leadership and the second under Herrnstein's. In each period, graduate students flocked to the leader and then began stimulating one another. Chance favored Herrnstein's leadership, too, because an unusually large number of graduate students were admitted in the fall of 1962. In each period, productivity declined as the leader lost interest in the laboratory and withdrew. Directly and indirectly, the laboratory finally died as a result of the cognitive "revolution." Skinner and his students saw the possibility of a natural science of behavior and set about establishing that science based on concepts such as response rate, stimulus control, and schedules of reinforcement. Herrnstein and his students saw that the science could be quantitative and set about making it so, with relative response rate, the matching law, and the psychophysics of choice (analogous to S. S. Stevens' psychophysics). The history might provide a golden research opportunity for someone interested in the impact of such self-organizing research groups on the progress of science.

Animals↗

PubMed2002

Choice in a variable environment: effects of blackout duration and extinction between components.

Pigeons were trained in a procedure in which sessions included seven four- or 10-reinforcer components, each providing a different reinforcer ratio that ranged from 27:1 to 1:27. The components were arranged in random order, and no signals differentiated the component reinforcer ratios. Each condition lasted 50 sessions, and the data from the last 35 sessions were analyzed. Previous results using 10-s blackouts between components showed some carryover of preference from one component to the next, and this effect was investigated in Experiment 1 by varying blackout duration from 1 s to 120 s. The amount of carryover decreased monotonically as the blackout duration was lengthened. Preference also decreased between reinforcers within components, suggesting that preference change during blackout might follow the same function as preference change between reinforcers. Experiment 2 was designed to measure preference change between components more directly and to relate this to preference change during blackout. In two conditions a 60-s blackout occurred between components, and in two other conditions a 60-s period of unsignaled extinction occurred between components. Preference during the extinction period progressively fell toward indifference, and the level of preference following extinction was much the same as that following blackout. Although these results are consistent with Davison and Baum's (2000) theory of the effects of reinforcers on local preference, other findings suggest that theory is incomplete: After a sequence of reinforcers from one alternative, some residual preference remained after 60 s of extinction or blackout, indicating the possibility of an additional longer term accumulation of reinforcer effects than originally suggested.

Animals↗

PubMed2002

Group foraging sensitivity to predictable and unpredictable changes in food distribution: past experience or present circumstances?

The ideal free distribution theory (Fretwell & Lucas, 1970) predicts that the ratio of foragers at two patches will equal the ratio of food resources obtained at the two patches. The theory assumes that foragers have "perfect knowledge" of patch profitability and that patch choice maximizes fitness. How foragers assess patch profitability has been debated extensively. One assessment strategy may be the use of past experience with a patch. Under stable environmental conditions, this strategy enhances fitness. However, in a highly unpredictable environment, past experience may provide inaccurate information about current conditions. Thus, in a nonstable environment, a strategy that allows rapid adjustment to present circumstances may be more beneficial. Evidence for this type of strategy has been found in individual choice. In the present experiments, a flock of pigeons foraged at two patches for food items and demonstrated results similar to those found in individual choice. Experiment 1 utilized predictable and unpredictable sequences of resource ratios presented across days or within a single session. Current foraging decisions depended on past experience, but that dependence diminished when the current foraging environment became more unpredictable. Experiment 2 repeated Experiment I with a different flock of pigeons under more controlled circumstances in an indoor coop and produced similar results.

Animals↗

PubMed2002

From molecular to molar: a paradigm shift in behavior analysis.

A paradigm clash is occurring within behavior analysis. In the older paradigm, the molecular view, behavior consists of momentary or discrete responses that constitute instances of classes. Variation in response rate reflects variation in the strength or probability of the response class. The newer paradigm, the molar view, sees behavior as composed of activities that take up varying amounts of time. Whereas the molecular view takes response rate and choice to be "derived" measures and hence abstractions, the molar view takes response rate and choice to be concrete temporally extended behavioral allocations and regards momentary "responses" as abstractions. Research findings that point to variation in tempo, asymmetry in concurrent performance, and paradoxical resistance to change are readily interpretable when seen in the light of reinforcement and stimulus control of extended behavioral allocations or activities. Seen in the light of the ontological distinction between classes and individuals, extended behavioral allocations, like species in evolutionary taxonomy, constitute individuals, entities that change without changing their identity. Seeing allocations as individuals implies that less extended activities constitute parts of larger wholes rather than instances of classes. Both laboratory research and everyday behavior are explained plausibly in the light of concrete extended activities and their nesting. The molecular- view, because it requires discrete responses and contiguous events, relies on hypothetical stimuli and consequences to account for the same phenomena. One may prefer the molar view on grounds of elegance, integrative power, and plausibility.

Animals↗