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Biomedical subjects

J A Nevin

Publications and source records attributed to J A Nevin.

43 records · Page 3Linked to original sources
PubMed1968

Differential reinforcement and stimulus control of not responding.

Pigeons were trained to respond with equal variable-interval reinforcement in the presence of a white key and also a white key with a vertical line. They were then trained not to respond to the vertical line by extinguishing the response or by reinforcing its non-occurrence at various frequencies. During training, the rate of key-pecking in the presence of the white key, maintained by a constant variable-interval schedule of reinforcement, depended on the frequency of reinforcement in the presence of the line. When lines of different orientations were presented in a generalization test, birds trained with extinction responded more to other orientations than to the vertical line, whereas those trained with high frequencies of reinforcement for not responding tended to respond equally at all line orientations. Intermediate frequencies of reinforcement gave mixed results.

Journal Article↗
PubMed1967

Effects of reinforcement scheduling on simultaneous discrimination performance.

Pigeons were trained on a discrete-trials, simultaneous discrimination procedure, with confusable stimuli such that asymptotic performance was about 85% correct. Trials were terminated if no response occurred within 2 sec of stimulus onset, so that probability of responding was free to vary. The schedule of reinforcement for correct responses was varied, with the following results: (1) there was no relation between frequency of reinforcement and accuracy of responding. (2) In extinction, the probability of responding fell to low levels, but accuracy remained roughly constant. (3) When reinforcement was available after a fixed number of trials or after a fixed number of correct responses, the probability of responding increased with successive trials after reinforcement, but accuracy was generally constant. (4) When every fifth correct response was reinforced, accuracy decreased immediately after reinforcement if the birds were required to respond on every trial.

Animals↗
PubMed1967

Some effects of correlation between response-contingent shock and reinforcement.

Rats responded on a two-component chain schedule in which a response-contingent electric shock at the end of the first component was either positively correlated, negatively correlated, or uncorrelated with reinforcement availability in the second component. With 0.4-ma shocks, rate in the first component depended on the shock-reinforcement correlation: when shock and reinforcement availability were positively correlated, after extended exposure to the contingencies, rates exceeded those in the absence of shock; when shock and reinforcement availability were negatively correlated, responding was generally suppressed throughout. The discriminative control of shock over responding in the second component, in which reinforcement was available 50% of the time, also depended somewhat on correlation. However, rate change in the first component was not specifically related to discrimination in the second component. With 0.8-ma shocks, responding was substantially suppressed in the first component at all three values of shock-reinforcement correlations.

Animals↗
PubMed1966

An analysis of contrast effects in multiple schedules.

Some phenomena of behavioral contrast in multiple schedules are reviewed, and three accounts of contrast are considered. Rate changes within a constant schedule component (transient contrasts) are distinguished from rate changes across successive schedule cycles (sustained contrasts). Pigeons were exposed to a three-component multiple schedule, in which a stimulus correlated with a constant variable interval schedule of reinforcement was preceded by a stimulus correlated with more frequent variable interval reinforcement, or by an extinction stimulus. If the preceding stimulus was correlated with more frequent reinforcement, the response rate in the constant component was low and increased with time. If the preceding stimulus was correlated with extinction, the rate in the constant component was high and decreased with time. Similar transient contrasts were observed in a two-component multiple schedule with different variable interval schedules in the two components. The transient contrast effects in the three-component schedule were shown to depend on differential reinforcement frequency rather than differential response rate in the preceding component. Such transient contrasts were not sufficient to account for sustained contrast effects observed in these experiments. The relation of these findings to the concepts of excitation and inhibition is discussed.

Animals↗
PubMed1963

Acquisition of delayed matching in the pigeon.

Pigeons were exposed to three successive matching-to-sample procedures. On a given trial, the sample (red, green or blue light) appeared on a center key; observing responses to this key produced the comparison stimuli on two side keys. Seven different experimental conditions could govern the temporal relations between the sample and comparison stimuli. In the "simultaneous" condition, the center key response was followed immediately by illumination of the side key comparison stimuli, with the center key remaining on. In "zero delay" the center key response simultaneously turned the side keys on and the center key off, while in the "variable delay" conditions, intervals of 1, 2, 4, 10, and 24 sec were interposed between the offset of the sample and the appearance of the comparison stimuli on the side keys. In all conditions, a response to the side key of matching hue produced reinforcement, while a response to the non-matching side key was followed by a blackout. In procedure I all seven experimental conditions were presented in randomly permutated order. After nine sessions of exposure (at 191 trials per session, for a total of 1719 trials) the birds gave no evidence of acquisition in any of the conditions. They were therefore transferred to Procedure II, which required them to match only in the "simultaneous" condition, with both the sample and comparison stimuli present at the same time. With the exception of one bird, all subjects acquired this performance to near 100% levels. Next, in Procedure III, they were once more exposed to presentation of all seven experimental conditions in random order. In contrast to Procedure I, they now acquired the delay performance, and were able to match effectively at delays of about 4 sec.

Journal Article↗