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E HEARST

Publications and source records attributed to E HEARST.

17 recordsLinked to original sources
PubMed1965

STRESS-INDUCED BREAKDOWN OF AN APPETITIVE DISCRIMINATION.

Rats trained to discriminate between S(D) and S(Delta) for food reinforcement showed marked impairments in this discrimination when strong, unavoidable shocks occurred at the termination of a third stimulus. The predominant feature of this impairment was a supernormal rate of unreinforced (S(Delta)) behavior. Shocks delivered without exteroceptive warning also led to a discriminative breakdown. The effect was a direct function of shock intensity. When behavior was strongly suppressed in the third stimulus by response-correlated shock ("punishment"), instead of unavoidable shock, breakdowns were only temporary; as soon as responding recovered from its overall suppression, discriminative performance returned to normal. The discriminative deterioration may be interpreted as an emotional by-product of frequent aversive stimulation, but accidental contingencies could also have played a role.

Appetite↗
PubMed1964

SELF-PRESENTATION AND SELF-TERMINATION OF A CONFLICT-PRODUCING STIMULUS.

Rats could press a lever to initiate or terminate a stimulus that was associated with intermittent rewards and punishments. Subjects spent time in both the stimulus-on and stimulus-off condition and oscillated frequently between the two conditions. This method provides continuous, quantitative records of oscillatory behavior and is sensitive to manipulations of shock intensity and food deprivation as well as the relative frequency of reward and punishment.

Animals↗
PubMed1964

STIMULUS GENERALIZATION AND THE RESPONSE-REINFORCEMENT CONTINGENCY.

Generalization gradients along a line-tilt continuum were obtained from groups of pigeons that had been trained to peck a key on different schedules of reinforcement. In Exp. I, gradients following training on a differential-reinforcement-of-low-rate (DRL) schedule proved to be much flatter than gradients following the usual 1-min variable interval (VI) training. In Exp. II, the value of the VI schedule itself was parametrically studied; Ss trained on long VI schedules (e.g., 4-min) produced much flatter gradients than Ss trained on short VI schedules (30-sec; 1-min). The results were interpreted mainly in terms of the relative control exerted by internal, proprioceptive cues on the different reinforcement schedules. Several implications of the results for other problems in the field of stimulus generalization are discussed.

Animals↗
PubMed1962

Adjustment of monkeys to five continuous days of work.

The efficiency of well-trained monkeys improved after repeated exposures to a prolonged task. This result suggests that resistance to fatigue may be increased by prior experience with the fatiguing situation.

Adaptation, Psychological↗
PubMed1962

Concurrent generalization gradients for food-controlled and shock-controlled behavior.

In the presence of a bright light, monkeys were trained to press a lever to avoid shock and to pull a chain for food reward. After gradients of generalization to other light intensities had been determined for each response, gradients were subsequently secured after training in a brightness discrimination and under several free-shock conditions. The following results were obtained: (1) Generalization gradients prior to discrimination training were much steeper for the food-controlled response than for the shock-controlled response. This finding was confirmed in another study in which rats served as subjects. (2) After discrimination training, both gradients became much steeper, but the avoidance gradient still showed more generalized responding than that of reward. (3) After a period of continuous testing with all the different test intensities, the two gradients became even steeper. In addition, differences between the two gradients virtually disappeared. (4) The intermittent delivery of free shocks during a previously non-shocked light intensity radically affected the shape of the avoidance gradient, just as the addition of an avoidance contingency did during the same, previously non-shocked, light intensity.

Animals↗
PubMed1962

Delayed alternation in the pigeon.

Pigeons were studied in a delayed-response task requiring alternation of key pecks on two response keys. Blackouts of from 1 to 10 sec intervened between successive choices on the two keys. THE FOLLOWING RESULTS WERE OBTAINED: (1) Birds performed at well above chance accuracy on all the delays tested. Accuracy was generally lowest at 1- and 10-sec delays. (2) Overt postural orientations during the delay interval appeared to mediate accurate key-pecking behavior. (3) The shape of the delay vs. accuracy function was discussed in terms of the possibly confounding influences of (a) stimulus "trace" variables, and (b) aversive effects of the time outs produced by incorrect responding.

Animals↗
PubMed1960

Simultaneous generalization gradients for appetitive and aversive behavior.

In the presence of a bright light five monkeys were trained to press a lever to avoid shock and to pull a chain for food reward. When tested with a series of lights dimmer than the conditioning stimulus, the monkeys showed a sharp gradient of effect for the rewarded response, in contrast to a very flat gradient for the avoidance response.

Animals↗