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E A Wasserman

Publications and source records attributed to E A Wasserman.

51 records · Page 3Linked to original sources
PubMed1981

Trace autoshaping: Acquisition, maintenance, and path dependence at long trace intervals.

The pigeon's tendency to acquire and maintain signal-directed key pecking under a trace conditioning procedure was parametrically examined. In Experiment 1, the percentage of CS trials with a key peck response was a decreasing function of the trace interval for separate groups of pigeons. The majority of subjects acquired signal-directed key pecking with trace intervals as long as 36 sec. In Experiment 2, differential maintenance of key pecking occurred across trace intervals in a within-subject procedure. Maintenance of key pecking at 36- and 60-sec trace intervals was path dependent in that responding depended on the subject's performance under the preceding trace interval.

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PubMed1981

Effects of differential reinforcement expectancies on successive matching-to-sample performance in pigeons.

A series of experiments employed a symbolic variant of Konorski's delayed successive matching-to-sample task in order to determine whether differential reinforcement expectancies affect discriminative responding. One of two sample stimuli (S1 or S2) was followed, after a delay (0, 5, or 10 sec), by one of two test stimuli (T1 or T2). Pigeons' key pecking during test periods could produce food only on S1-T1 and S2-T2 (positive) trials; nonreinforcement invariably occurred on S1-T2 and S2-T1 (negative) trials. Differential reinforcement was scheduled by following the two positive trial sequences with different probabilities of reinforcement (.2 and 1.0); nondifferential reinforcement was scheduled by following the two positive trial sequences with a single, intermediate probability of reinforcement. (.6). Subjects given differential reinforcement acquired the conditional discriminaton more rapidly and reached higher terminal levels of performance than nondifferential controls (Experiment 1). Moreover, the magnitude of these differences increased as the delay between sample and test stimuli was lengthened. Reversing the probabilities of reinforcement in the differential problem produced a substantial and durable disruption of conditional discrimination performance (Experiment 2). The same general pattern of results was obtained when differential sample key pecking was eliminated (Experiment 3). These results can be parsimoniously interpreted by postulating the existence of learned reinforcement expectancies, and they detract from the merits of trace theory as a complete account of animal memory.

Animals↗
PubMed1980

Memory for sequences of stimuli and responses.

Two experiments sought to determine if pigeons could discriminate and remember recent sequences of stimuli and responses. A variant of Konorski's short-term memory procedure involving successive presentation of sample and test stimuli was used. The samples were stimulus-response pairs of the form, (S-R)(1)-(S-R)(2). Differential test responding disclosed memory of the two-item samples, with birds showing earlier and greater control by the second item than the first (Experiment 1). When the retention interval separating the second item of the sample sequence from the test stimulus was lenghtened from .5 to 2.0 or 4.0 sec, a systematic loss of stimulus control resulted; however, when varied over the same temporal range, the interval between the two items of the sample sequence had a much smaller effect, or none at all (Experiment 2). These results support an account of response-sequence differentiation that stresses short-term memory of organized behavior patterns.

Journal Article↗
PubMed1979

Conditioning of two-response patterns of key pecking in pigeons.

On discrete trials, two response keys were made available to hungry pigeons and food reinforcement depended on the order in which the required two key pecks occurred. In different phases, only one of the four possible two-peck sequences (left-left, left-right, right-left, and right-right) produced food reinforcement. In each case, the pigeons learned to perform the correct two-peck sequence more often than the incorrect sequences. Furthermore, the course of differentiation mastery indicated that both reinforcement history and response-reinforcer contiguity influenced performance. These results reveal that response patterns comprising two instances of the same response left-left and right-right) or instances of two different responses (left-right and right-left) may function as operants, thereby extending the generality of conditioning principles from discrete responses to structured sequences of behavior. These and other results are discussed in terms of contiguity-based and memory-based models of learning.

Journal Article↗
PubMed1978

Temporal factors influencing the pigeon's successive matching-to-sample performance: sample duration, intertrial interval, and retention interval.

A successive matching-to-sample procedure that entails the sequential presentation of sample and test stimuli and the monitoring of response rates in a go/no-go discrimination of matching and nonmatching stimuli was studied as an alternative to the familiar delayed-matching paradigm of animal short-term memory. Three within-subject experiments studied the effects of sample duration (1 to 12 seconds), intertrial interval (5 to 50 seconds), and retention interval (1 to 50 seconds) on the pigeon's successive-matching performance. The results revealed that retention was (a) an increasing function of sample duration and intertrial interval, and (b) a decreasing function of retention interval. These results were in accord with those of more traditional short-term memory paradigms, and reveal the suitability of the successive-matching procedure for studying memory processes.

Journal Article↗
PubMed1977

Rate and temporal pattern of key pecking under autoshaping and omission schedules of reinforcement.

The role of response-reinforcer contiguity on autoshaped key pecking in pigeons was studied by scheduling response-dependent nonreinforcement at the beginning or the end of brief (8-sec) discrete trials. Schedules that permitted chance conjunctions of key pecking and food sustained high rates of responding, whereas those that prevented the occurrence of key peck-food intervals shorter than 4 sec sustained low response rates. In addition, selective reinforcement schedules supported accelerating or decelerating rates of responding within individual trials. These effects were traceable to response-reinforcer (operant), but not stimulus-reinforcer (respondent) factors.

Journal Article↗
PubMed1977

Conditioning of within-trial patterns of key pecking in pigeons.

The possibility of conditioning systematic patterns of responding during brief discrete trials was studied by requiring hungry pigeons to key peck and then pause or to pause and then key peck in order to gain access to food. These schedules were highly effective in promoting decelerated and accelerated rates of responding, respectively, within individual trials; indeed, performance was quite similar to that observed when explicit external stimuli were correlated with "peck" and "pause" portions of the daily trials. Finally, schedules of reinforcement that did not selectively reinforce peck-pause or pause-peck patterns neither generated these patterns nor maintained them at the previous high levels. The results, therefore, confirm Shimp's (1976) proposal that organized groupings of discrete responses may function as operants-even in the absence of strict response-reinforcer contiguity.

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PubMed1974

The disruption of autoshaped key pecking in the pigeon by food-tray illumination.

Two experiments investigated the effect of food-tray illumination on pecking a lighted key that signalled food presentation. Pigeons key pecked less when both feeder and key stimuli preceded grain delivery than when the keylight alone signalled food. This detractive influence of grain-tray illumination did not result after prior pairings of the keylight with food. The involvement of associative and physical variables in autoshaping the pigeon's key peck is considered in light of these findings.

Journal Article↗
PubMed1974

Differential autoshaping to common and distinctive elements of positive and negative discriminative stimuli.

The learning by hungry pigeons of a discrimination between two successively presented compound visual stimuli was investigated using a two-key autoshaping procedure. Common and distinctive stimulus elements were simultaneously presented on separate keys and either followed by food delivery, S+, or not, S-. The subjects acquired both between-trial and within-trial discriminations. On S+ trials, pigeons pecked the distinctive stimulus more than the common stimulus; before responding ceased on S- trials, they pecked the common stimulus more than the distinctive one. Mastery of the within-display discrimination during S+ trials preceded mastery of the between-trials discrimination. These findings extend the Jenkins-Sainsbury analysis of discriminations based upon a single distinguishing feature to discriminations in which common and distinctive elements are associated with both the positive and negative discriminative stimuli. The similarity of these findings to other effects found in autoshaping-approach to signals that forecast reinforcement and withdrawal from signals that forecast nonreinforcement-is also discussed.

Journal Article↗
PubMed1969

Olfactory stimuli and the "pseudo-extinction" effect.

Continuously rewarded rats show a decrease in running speed on a runway recently traversed by other rats undergoing experimental extinction. This "pseudo-extinction" effect is caused by discriminable odors emitted by extinction subjects. These odors could be confounding variables in studies using forms of aversive stimulation.

Animals↗
PubMedDate not supplied

The relationship between motor and secretory behaviors in classical appetitive conditioning.

Three hungry dogs received pairings of food with an accessible, illuminated panel. This resulted in the dogs' approaching the lighted panel and salivating. Despite the similarity of these conditioning procedures to those used in a large body of research primarily with avians, however, the dogs did not physically contact the lighted stimulus panel. These results bear on several issues concerning the form and direction of classically conditioned behaviors.

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