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Biomedical subjects

H S HOFFMAN

Publications and source records attributed to H S HOFFMAN.

At least 19 recordsLinked to original sources
PubMed1965

STIMULUS ASPECTS OF AVERSIVE CONTROLS: THE EFFECTS OF RESPONSE CONTINGENT SHOCK.

A tone ending with electrical shock was periodically presented to pigeons while they pecked a key for food. Pairs of birds were run simultaneously under a yoked program which insured that both birds received the same number and temporal distribution of shocks. For one of the birds, shock was always initiated by a peck; for the other, shock was unavoidable. Both procedures led to reduced rates of pecking in the presence of the tone, and gradients of stimulus generalization were obtained. But the effects of response contingent shock extinguished more rapidly than the effects of unavoidable shock. In general, birds exposed to unavoidable shock tended to respond at intermediate rates throughout tone, whereas those exposed to response contingent shock ceased to peck for part or all of the tone period.

Animals↗
PubMed1964

STIMULUS ASPECTS OF AVERSIVE CONTROLS: STIMULUS GENERALIZATION OF CONDITIONED SUPPRESSION FOLLOWING DISCRIMINATION TRAINING.

A tone ending with unavoidable electrical shock was periodically presented to pigeons while they pecked a key for food. A second group of birds was exposed to these tone-shock contingencies and also to a second tone which never ended with shock. The gradient of stimulus generalization following training to a single stimulus was symmetrical, whereas the gradient following discrimination training was asymmetrical, but there was no evidence of peak shift. During testing, suppression to all tones gradually extinguished and in both groups the slope of the gradient increased markedly. A second experiment with the discrimination birds revealed that free shock caused a recovery of the gradient, but the asymmetry persisted.

Animals↗
PubMed1963

STARTLE REACTION: MODIFICATION BY BACKGROUND ACOUSTIC STIMULATION.

Six rats were exposed to a sequence of gunshot-like acoustical bursts during silence, during steady noise, and during pulsed noise. Assessment of their startle reactions to the bursts revealed that a background of steady noise enhanced the response, whereas a background of pulsed noise produced suppression of response. It is hypothesized that pulsed noise causes a relative refractory state in the mechanisms responsible for startle and that steady noise may enhance startle by masking uncontrolled punctiform acoustic stimuli.

Acoustic Stimulation↗
PubMed1963

STIMULUS ASPECTS OF AVERSIVE CONTROLS: THE RETENTION OF CONDITIONED SUPPRESSION.

Three years ago a tone ending in unavoidable electrical shock was periodically presented to pigeons while they pecked a key for food. When pecking was disrupted by tone, shock was disconnected and the training tone as well as tones of different frequencies were presented. At first, all tones caused a reduction in the rate of pecking, but as testing proceeded, suppression began to extinguish and the gradient narrowed. In the present work, testing was resumed after a 2(1/2)-yr interruption. Analysis of the gradients obtained just before and just after the interruption yielded no evidence of changes with the passage of time. As testing proceeded, however, extinction of suppression continued and the gradient all but disappeared. In subsequent experiments with these subjects (Ss) it was found that the presentation of free shocks caused a reappearance of the gradient and that this effect persisted in reduced amount for several sessions after the shock condition was terminated.

Animals↗
PubMed1962

Aversive training: long-term effects.

Three years ago a tone ending in unavoidable electric shock was periodically presented to pigeons while they pecked a key for food. When pecking was disrupted by tone, shock was disconnected and the training tone and tones of different frequencies were presented. At first all tones caused a reduction in the rate of pecking, but as testing proceeded the gradient narrowed. In our study, testing was resumed after a 2(1/2)-year interruption. Despite the interruption the tones still suppress behavior.

Animals↗
PubMed1961

Stimulus generalization of conditioned suppression.

A tone ending in unavoidable electric shock was periodically presented to pigeons while they pecked a key for food. When pecking was completely disrupted by tone, shock was disconnected, and the training tone and tones having new frequencies were presented. Initially the gradient of generalization was broad; as testing proceeded, however, the gradient narrowed severely.

Animals↗