Biomedical subjects

A J Brownstein

Publications and source records attributed to A J Brownstein.

8 recordsLinked to original sources

PubMed1986

Rule-governed behavior and sensitivity to changing consequences of responding.

Humans were presented with a task that required moving a light through a matrix. Button presses could produce light movements according to a multiple fixed-ratio 18/differential-reinforcement-of-low-rate 6-s schedule, with components alternating every 2 min. Moving the light through the maze earned points worth chances on money prizes. In Experiment 1 four conditions were assessed through between-subject comparisons: minimal instructions, instructions to press rapidly, instructions to press slowly, and instructions that sometimes rapid responding would work while at other times a slow rate would work best. Subjects responded in three successive sessions of 32 min each. The results suggested that instructions affected the nature of the contact made with the programmed consequences and thus subsequent performance. In some cases, responding seemed to result from added contingencies introduced by stating rules. In Experiment 2 the relative contribution of these two effects was assessed by presenting and then withdrawing two lights that had been paired with two specific instructions: "Go Fast" or "Go Slow." There were three conditions. In one condition, only the Go Fast light was on; in a second, only the Go Slow light was on; and in a third, the lights alternated each minute. In each condition, half the subjects had all instruction lights turned off after the first session. The results once again showed an effect of instructions on contact with the programmed consequences. However, responding sometimes continued in a manner consistent with added contingencies for rule-following even when the programmed consequences had been contacted and would have controlled a different type of responding in the absence of instructions. The relevance of added contingencies for rule-following in determining the effects of explicitly programmed consequences is emphasized.

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PubMed1986

Instructions, multiple schedules, and extinction: Distinguishing rule-governed from schedule-controlled behavior.

Schedule sensitivity has usually been examined either through a multiple schedule or through changes in schedules after steady-state responding has been established. This study compared the effects of these two procedures when various instructions were given. Fifty-five college students responded in two 32-min sessions under a multiple fixed-ratio 18/differential-reinforcement-of-low-rate 6-s schedule, followed by one session of extinction. Some subjects received no instructions regarding the appropriate rates of responding, whereas others received instructions to respond slowly, rapidly, or both. Relative to the schedule in operation, the instructions were minimal, partially inaccurate, or accurate. When there was little schedule sensitivity in the multiple schedule, there was little in extinction. When apparently schedule-sensitive responding occurred in the multiple schedule, however, sensitivity in extinction occurred only if differential responding in the multiple schedule could not be due to rules supplied by the experimenter. This evidence shows that rule-governed behavior that occurs in the form of schedule-sensitive behavior may not in fact become schedule-sensitive even though it makes contact with the scheduled reinforcers.

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PubMed1978

Effect of varying the duration of grain presentation on automaintenance.

In a series of three experiments the effects of variation in grain duration on automaintenance were evaluated. In the first experiment, key illumination was followed by grain only when pigeons did not peck the key. Each subject was exposed to 2-, 4-, and 8-second feeder durations in blocks of 10 sessions. Subjects pecked on a high percentage of trials at all feeder durations. The mean peck latency was shorter in the 8-second condition than in the two other conditions in five of six subjects. The conditional probability of pecking given successive keylight-grain pairings did not increase as the number of pairings increased. The second experiment was identical to the first, except that key pecking had no scheduled consequence. Under these conditions, all three subjects showed substantial responding. The recorded measures showed no systematic relationship to feeder duration in this study. In the third experiment, two different stimuli were followed by feeder presentations of either identical (2- or 8-second) or different (2- and 8-second) durations within each session. Subjects tended to respond sooner and with a higher overall rate in the presence of the stimulus associated with the longer feeder duration only when different feeder durations were presented within the same session. This result was confirmed by direct observation of the pigeons. The results of these experiments suggest that the effects of varying grain duration may be small, compared to the effects of varying other variables. The results also suggest that the location as well as the frequency of pecking may be an important measure in the analysis of factors controlling the pigeon's key peck.

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PubMed1975

Response-rate invariance in concurrent schedules: effects of different changeover contingencies.

In a two-key chamber, one key (the food key) was either red or green with different variable-interval schedules operating concurrently in each color and a second key (the changeover key) served to change the food-key color. Three pigeons were trained with either a 2-sec changeover delay or a 0-sec changeover delay and three birds with a fixed-ratio 2 on the changeover key instead of a changeover delay. The proportion of time spent in red approximated the proportion of reinforcers delivered in red for all birds. When the procedure was changed so that reinforcers were signalled in the green schedule, rates of reinforcement were unaltered, but the pigeons spent virtually the whole session in red. Changeovers to green were allowed only when a reinforcer was assigned by the schedule associated with green. For all pigeons with the fixed-ratio requirement on the changeover key or with a 0-sec changeover delay, the overall rate of red-key responses was higher during the signalling condition than during unsignalled, or baseline, condition. The present data question the generality of previous reports that the rate of one response is independent of the amount of time allocated to the alternative response.

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PubMed1975

Time allocation on concurrent schedules with asymmetrical response requirements.

Pigeons were trained on concurrent schedules in which key pecking was required by both schedules (concurrent variable-interval variable-interval schedules) and on concurrent schedules in which key pecking was required by only one of the schedules (concurrent variable-interval variable-time schedules). The distribution of reinforcements was systematically varied with both types of concurrent schedules. The distribution of time between the schedules depended on the reinforcement distribution and was independent of the symmetry of the response requirement. The relation between time and reinforcement distributions appears to be invariant over a wide range of manipulations of responding maintained by concurrent schedules.

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PubMed1971

Concurrent schedules of response-independent reinforcement: duration of a reinforcing stimulus.

Presentations of grain to three pigeons were determined by two response-independent schedules. Interpresentation intervals varied with a mean interval of 1.5 min for each schedule. Both were concurrently operative, but grain was presented by one only when the chamber was illuminated with blue light and by the other only during amber illumination. A response on a white key, the only key in the chamber, alternated the stimulus conditions and the effective schedule. Grain presentation durations associated with the illumination conditions were varied from 1.5 to 4.5 sec. The proportion of the total session time spent in an illumination condition closely approximated the relative grain presentation duration provided in that illumination. For two of the birds, the proportion of the total number of grain presentations obtained in an illumination condition was an increasng function of the presentation duration in that illumination.

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PubMed1970

Interresponse time duration in fixed-interval schedules of reinforcement: control by ordinal position and time since reinforcement.

The times between each of the first thirteen responses after reinforcement (the first twelve interresponse times) were determined for two pigeons whose pecking was reinforced on fixed-interval schedules of food reinforcement ranging from 0.5 min to 5 min. These interresponse times were classified with respect to their ordinal position in the sequence of responses and with respect to the time since the preceding reinforcement at which the initiating response occurred. The median interresponse time durations were essentially constant after the sixth response after reinforcement regardless of the time at which the interresponse time was initiated. The durations of the first few interresponse times after reinforcement decreased as the number of preceding responses increased and as the time since the preceding reinforcement increased.

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PubMed1968

Some effects of relative reinforcement rate and changeover delay in response-independent concurrent schedules of reinforcement.

Reinforcements were arranged independently of the pigeon's behavior by concurrent variable-interval schedules. The reinforcements arranged by one of the schedules occurred when the chamber was illuminated with amber light, and the reinforcements arranged by the other schedule occurred when the chamber was illuminated with blue light. Both schedules functioned concurrently, but reinforcers were delivered by each only in the presence of the appropriate stimulus condition. A response on a white key, the only key in the chamber, alternated the stimulus condition and the effective schedule. The results of this procedure were similar to those obtained with concurrent response-dependent variable-interval schedules of reinforcement. The proportion of the total session time spent in the presence of a schedule component approximated the proportion of the total number of reinforcements in the component. Changeover rate was a decreasing function of the changeover delay and of the difference between the relative rates of reinforcement for each pair of concurrent schedules.

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