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Biomedical subjects

B Schwartz

Publications and source records attributed to B Schwartz.

At least 397 records · Page 22Linked to original sources
PubMed1973

The maintenance of key pecking by stimulus-contingent and response-independent food presentation.

Three naive pigeons were exposed to a series of two-component multiple schedules of response-independent food presentation. The component schedules were sometimes identical (non-differential procedures) and sometimes different (differential procedures). High rates of key pecking were maintained in all the differential procedures, and pecking decreased substantially in non-differential procedures, even when the frequency of food presentation in non-differential procedures was higher than in differential procedures. It is suggested that the high rates of key pecking were maintained not by adventitious response-reinforcer contingencies, but by differential contingencies between the stimulus (keylight) and food. The role of such contingencies in the phenomenon of behavioral contrast is discussed.

Journal Article↗
PubMed1973

Maintenance of key pecking by response-independent food presentation: the role of the modality of the signal for food.

Three pigeons were exposed to a series of procedures in which periods of response-independent food presentation, on a variable-time schedule, alternated with periods in which food was never presented. The stimuli that signalled periods of food availability or non-availability varied from one procedure to the next, and were sometimes key colors, sometimes tones, and sometimes compounds of both. Key pecking was initiated and maintained when key color was a signal for food; key pecking was not initiated when a tone was the signal for food. However, control of key pecking that was already established could be transferred from key color to tone, and subsequently, initiated by the tone. It is suggested that for pigeons, pre-experimental relationships exist among food, visual stimuli, and pecking, and that a similar relationship, which includes auditory stimuli, must be induced in the laboratory.

Journal Article↗
PubMed1972

The role of the response-reinforcer contingency in negative automaintenance.

When a response key is briefly illuminated before a grain reinforcer is presented, key pecking is reliably developed and maintained in pigeons, even if pecking prevents reinforcement (negative automaintenance). This experiment demonstrated that pigeons are sensitive to a negative response-reinforcer contingency, even though it does not eliminate responding. Within individual pigeons, two kinds of trials were compared: red key trials, in which reinforcement was negatively contingent on responding, and white key trials, in which reinforcement was unrelated to responding. Reinforcement frequency in non-contingent trials was yoked to the obtained reinforcement frequency in negatively contingent trials. All eight pigeons pecked substantially more on the non-contingent key than on the negative key, and preferred the non-contingent key to the negative key on occasional "choice" trials where both were presented together. When the stimuli correlated with the two conditions were reversed, the pigeons' behavior also shifted. These response differences are taken as evidence that pigeons are sensitive to the negative response-reinforcer contingency.

Journal Article↗
PubMed1972

Two different kinds of key peck in the pigeon: some properties of responses maintained by negative and positive response-reinforcer contingencies.

Pigeons emitted almost exclusively short-duration key pecks (shorter than 20 msec) when on negative automaintenance procedures, in which pecks prevented reinforcement. Peck durations under fixed-interval and fixed-ratio reinforcement schedules were generally two to five times longer than pecks under a negative automaintenance schedule. However, initial key pecks were of short duration, independent of procedure. The frequency of short-duration pecks was insensitive to differential reinforcement, while the frequency of long-duration pecks was sensitive to differential reinforcement. It is proposed that short-duration pecks arise from the pigeon's normal feeding pattern and are directly enhanced by food presentation, while long-duration pecks are controlled by the contingent effects of food presentation. The implications of the existence of two classes of pecks for the functional definition of operants and the separation of phylogenetic and ontogenetic sources of control of key pecking are discussed.

Journal Article↗