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Biomedical subjects

H Rachlin

Publications and source records attributed to H Rachlin.

31 records · Page 2Linked to original sources
PubMed1975

Economic and biological influences on a pigeon's key peck.

Pigeons were studied in a two-component multiple schedule. In the first phase of the experiment, key pecks were reinforced on a variable-interval 2-min schedule in both components and free food was delivered additionally during one component. When components alternated every 8 sec, all pigeons pecked at a much higher rate during the component with free food than during the other component. At a component duration of 16 min, the reverse was true: all pigeons pecked at a higher rate during the component without free food. In the second phase, the additional food during one component was made contingent on pecking. Responding during the component without the extra food remained essentially unchanged, as expected, since rate of reinforcement remained identical to that in the previous phase. However, rate of responding during the component with the extra food (now contingent on pecking) was elevated, compared to the rate in the first phase, and did not show the marked decline as component duration was increased.

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PubMed1972

Response control with titration of punishment.

Pigeons and rats were exposed to multiple schedules with different schedules of electric shock superimposed on identical schedules of food reinforcement during each of two components. During one component, (adjusting-intensity) the intensity of electric shock depended on responding. Each response increased the intensity while intensity decreased between responses. During the other component (constant-intensity) the intensity was fixed at the value at which it had been adjusted at the end of the immediately preceeding adjusting-intensity component. In one experiment, shock was continuous during both components. In another experiment, instead of continuous shock, a brief pulse was delivered immediately after each response. During the adjusting-intensity component of both experiments, pigeons and rats responded at a rate just sufficient to keep the shock constant (critical rate). During the constant-intensity component, responding depended on whether shock was delivered continuously or in pulses. When shock was continuous, response rate during the constant-intensity component was higher than the critical rate. When shock was pulsed, response rate during the constant-intensity component was equal to the critical rate.

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PubMed1972

Commitment, choice and self-control.

When offered a choice (Choice Y) between a small immediate reward (2-sec exposure to grain) and a large reward (4-sec exposure to grain) delayed by 4 sec, pigeons invariably preferred the small, immediate reward. However, when offered a choice (Choice X) between a delay of T seconds followed by Choice Y and a delay of T seconds followed by restriction to the large delayed reward only, the pigeon's choice depended on T. When T was small, the pigeons chose the alternative leading to Choice Y (and then chose the small, immediate reward). When T was large, the pigeons chose the alternative leading to the large delayed reward only. The reversal of preference as T increases is predicted by several recent models for choice between various amounts and delays of reward. The preference for the large delayed alternative with long durations of T parallels everyday instances of advance commitment to a given course of action. Such commitment may be seen as a prototype for self-control.

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PubMed1972

Effects of alternative reinforcement: does the source matter?

In a chamber with a single response key, pigeon's key pecks were reinforced with food according to a variable-interval schedule. In addition, extra reinforcements occurred concurrently according to an independent schedule. In one condition, availability of the extra reinforcements was signalled by a change in key color from white to red. The extra reinforcements occurred after a peck on the red key. In a second condition, the extra reinforcements were unsignalled and occurred only after a 2-sec pause in pecking for one group of subjects and were unsignalled and occurred freely as scheduled for another group of subjects. In the first two conditions, duration of reinforcement was varied. A third condition duplicated the second but varied rate rather than duration of reinforcement. The rate of pecking varied inversely with the amount of extra reinforcement per unit time according to the same function, regardless of the condition regulating occurrence of the extra reinforcements, and regardless of whether or not a 2-sec pause was required for their occurrence. The shape of this function was predicted by Herrnstein's (1970) matching law.

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PubMed1971

On the tautology of the matching law.

The generalized matching law, that organisms divide their time between alternatives in proportion to the value of the reinforcement consequent on the choice, is derivable from the assumption that an organism choosing between alternatives is under no constraints except those the contingencies of reinforcement impose. Hence, the law is not subject to empirical test. Its value lies in its simple codification of assumptions underlying choice experiments.

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PubMed1969

Response rate as a function of amount of reinforcement for a signalled concurrent response.

Pigeons were exposed to two equal, concurrent variable-interval schedules of reinforcement on two response keys. One key was continuously illuminated. Pecking on that key produced reinforcements of constant duration. The other key was normally dark, except that availability of reinforcement was signalled by illuminating the key. The duration of access to a grain reinforcer was varied on the key that signalled reinforcement. Rate of response on the first key, the one that did not signal reinforcement, was found to vary inversely with duration of signalled reinforcement on the other key. The latency between the signal and the peck that produced signalled reinforcement remained about constant. These results show that responding on one key in concurrent variable-interval schedules depends on the reinforcement delivered by both schedules and is independent of responding on the other key.

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PubMed1969

Notes on fixed-ratio and fixed-interval escape responding in the pigeon.

After learning to peck a key when each peck removed a slowly increasing series of electric shocks, pigeons were placed on fixed-ratio and fixed-interval escape schedules. The resulting behavior was comparable to that of other species on ratio and interval escape schedules. Thus, while the pigeon apparently requires special techniques for the initial shaping of a key-peck response with negative reinforcement, this response, once obtained, can be subjected to intermittent schedules of negative reinforcement with no great difficulty.

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PubMed1969

Autoshaping of key pecking in pigeons with negative reinforcement.

Pigeons exposed to gradually increasing intensities of pulsing electric shock pecked a key and thereby reduced the intensity of shock to zero for 2 min. Acquisition of key pecking was brought about through an autoshaping process in which periodic brief keylight presentations immediately preceded automatic reduction of the shock. On the occasions of such automatic reduction of shock preceding the first measured key peck, little or no orientation to the key was observed. Observations of pigeons with autoshaping of positive reinforcement also revealed little evidence of orientation toward the key.

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PubMed1969

Escape and avoidance of shock by pigeons pecking a key.

Pigeons had been trained to peck a key when each peck removed a slowly increasing series of electric shocks. Without loss of the established key-pecking response, the birds were gradually weaned from this procedure to one where intense shocks were presented suddenly, duplicating features that had proved ineffective for initial shaping of the response. Finally, a procedure was introduced in which key pecks could avoid shock. Avoidance responding was maintained in two of three pigeons.

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PubMed1968

Indifference between punishment and free shock: evidence for the negative law of effect.

Pigeons were trained to respond under two conditions with two identical variable-interval schedules of positive reinforcement. While the schedules operated for separate response keys, they were not available concurrently. During one condition, each response was punished with electric shock. During the other condition, shocks were delivered independently of responding. The punishment suppressed responding but the free shocks did not. However, when allowed to choose, the pigeons preferred the condition associated with the lowest rate of shock regardless of whether or not the shock was dependent on responding. In general, shocks exerted their greatest effect on whichever response had the greatest influence on shocks. In this respect, punishment is instrumental in suppressing behavior and the properties of punishment are symmetrical to those of reinforcement. This empirical symmetry dictates a corresponding conceptual symmetry in terms of a positive law of effect accounting for response increments and a negative law accounting for response decrements.

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PubMed1967

The effect of shock intensity on concurrent and single-key responding in concurrent-chain schedules.

Pigeons were trained to respond in a two-link, concurrent-chain schedule. Pecks on each key during the concurrent initial links occasionally produced a 5-min terminal link, during which only that key was operative. Food reinforcement and various intensities of shock were scheduled during the terminal links. When shock was contingent on response, the effect of shock was greater on terminal-link responding than on initial-link responding. When shock was independent of response, the effect was reversed, with larger changes in initial-link responding than terminal-link responding. In general, shock was found to affect behavior most drastically when behavior could, in turn, affect the rate of shock.

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PubMed1966

Recovery of responses during mild punishment.

Pigeons were punished with mild shock for pecking during one of two components of a multiple schedule. They eventually recovered so that they pecked at the same rate during both components. In one experiment they were extinguished after recovering. When punishment was maintained during extinction, they extinguished faster during the punished, than during the unpunished component. When punishment was stopped during extinction, they extinguished faster during the unpunished than during the previously punished component. In another experiment, punishment was programmed first during neither of the two components, then during one, then during both, and finally during the other component. The extent of recovery decreased with each successive cycle. It is concluded that, if transient emotional states are ignored, reward and punishment are symmetrical in their effects.

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