ISSN:0022-5002    

DOI:10.1901/jeab.1991.55-1

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Rats were trained on a successive discrete‐trial discrimination between two tonal stimuli to examine the effects of availability of a lever during intertrial intervals. In the discrete‐trial condition, in which a lever was removed from the chamber during intertrial intervals, 10‐s trials were initiated by the presentation of both discriminative stimulus and lever. In the free‐operant condition, in which a lever was present during both trials and intertrial intervals, 10‐s trials were initiated only by the presentation of a discriminative stimulus. Experiment 1 employed 50‐s intertrial intervals and demonstrated that discriminative performances were acquired faster and maintained better in the free‐operant conditions than in the discrete‐trial conditions. Experiment 2 employed 5‐s intertrial intervals and showed that poor discriminative performances in the discrete‐trial conditions were improved. These results indicate that the presentation of a lever to start a trial can overshadow or mask the control by a discriminative stimulus and thereby obstruct the acquisition and maintenance of discriminative performances. Furthermore, the overshadowing or masking effects are strengthened as a function of the duration of i

ISSN:0022-5002    

DOI:10.1901/jeab.1991.55-3

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The stimuli that control responding in the peak procedure were investigated by training rats, in separate sessions, to make two different responses for food reinforcement. During one type of session, lever pressing was normally reinforced 32 s after the onset of a light. During the other type of session, chain pulling was normally reinforced either 8 s after the onset of one auditory cue or 128 s after the onset of a different auditory cue. For both types of sessions, only the appropriate manipulandum was available, and 20% of the trials lasted 240 s and involved no response‐contingent consequences. Rats were then tested with the auditory cues in the presence of the lever and the light in the presence of the chain. If the time of reinforcement associated with each stimulus was learned, response rates should peak at these times during transfer testing. However, if a specific response pattern was learned for each stimulus, little transfer should occur. The results did not clearly support either prediction, leading to the conclusion that both a representation of the time of reinforcement and the rat's own behavior may control responding in this situatio

ISSN:0022-5002    

DOI:10.1901/jeab.1991.55-11

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Rats and pigeons were trained on a series of reversals of a conditional simultaneous discrimination. The percentage of reinforcement for correct trials was varied across reversals. When nonreinforced correct trials produced the same feedback as incorrect trials, the number of errors to reach an acquisition criterion was greater for smaller percentages of reinforcement, but the number of reinforcers required was either approximately constant or smaller for the smaller percentages. When a stimulus paired with food (the conditioned reinforcer) was added on nonreinforced correct trials, both measures were substantially decreased. When the same stimulus was presented, but without a history of food pairing, learning rate was similar to when no stimulus was presented on nonreinforced trials. The results provide direct evidence that conditioned reinforcers may substitute, although imperfectly, for a primary reinforcer, and that pairing with the primary reinforcer is a necessary condition for such substitutability to occur.

ISSN:0022-5002    

DOI:10.1901/jeab.1991.55-21

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Pigeons were presented with a concurrent‐chains schedule in which both choice alternatives led to the same terminal‐link stimulus, which was followed by food. Superimposed on the food‐reinforced presentations of the terminal‐link stimulus was a second schedule of presentations of the same stimulus that were followed by no food. The absolute number of these no‐food stimulus presentations was held constant while their relative frequency assigned to one or the other choice alternative was systematically varied. Preference for a given choice alternative tracked the relative frequency of these stimulus presentations, thus demonstrating that they served as reinforcers. These results resolve conflicts in the literature regarding the effect of conditioned reinforcement

ISSN:0022-5002    

DOI:10.1901/jeab.1991.55-37

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Six pigeons were trained on concurrent variable‐interval schedules in which responding on fixed‐interval schedules was required to give access to the alternate schedule. Responding on the concurrent schedules was not allowed, after changing over had commenced, until the changeover schedule had been completed. In Parts 1 to 3 of the experiment, the changeover fixed‐interval schedules were equal and were 0 s, 10 s, and 20 s, respectively. In each part, the relative frequency of reinforcement obtained on the concurrent schedules was varied over at least five conditions. In Part 4, the concurrent schedules were equal, and one changeover fixed‐interval schedule was twice the other. Under these conditions, the absolute sizes of the changeover schedules were varied. Increasing the changeover requirement from 0 s to 10 s (Parts 1 and 2) resulted in increases in the sensitivity of behavior allocation to reinforcers obtained, but no further increase was obtained when the changeover schedules were increased to 20 s (Part 3). In Part 4, performance was biased towards the concurrent schedule that took less time to enter. These results are consistent with a subtractive punishment model of travel in which the degree of punishment is measured by the number of reinforcers apparently lost from a schedule when the subject changes to that schedule. Absolute times spent on the main keys could be accurately described by a previous model of changeover perf

ISSN:0022-5002    

DOI:10.1901/jeab.1991.55-47

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Two experiments measured pigeons' choices between probabilistic reinforcers and certain but delayed reinforcers. In Experiment 1, a peck on a red key led to a 5‐s delay and then a possible reinforcer (with a probability of .2). A peck on a green key led to a certain reinforcer after an adjusting delay. This delay was adjusted over trials so as to estimate an indifference point, or a duration at which the two alternatives were chosen about equally often. In all conditions, red houselights were present during the 5‐s delay on reinforced trials with the probabilistic alternative, but the houselight colors on nonreinforced trials differed across conditions. Subjects showed a stronger preference for the probabilistic alternative when the houselights were a different color (white or blue) during the delay on nonreinforced trials than when they were red on both reinforced and nonreinforced trials. These results supported the hypothesis that the value or effectiveness of a probabilistic reinforcer is inversely related to the cumulative time per reinforcer spent in the presence of stimuli associated with the probabilistic alternative. Experiment 2 tested some quantitative versions of this hypothesis by varying the delay for the probabilistic alternative (either 0 s or 2 s) and the probability of reinforcement (from .1 to 1.0). The results were best described by an equation that took into account both the cumulative durations of stimuli associated with the probabilistic reinforcer and the variability in these durations from one reinforcer to the n

ISSN:0022-5002    

DOI:10.1901/jeab.1991.55-63

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Rats in a laboratory foraging simulation searched for sequential opportunities to feed in two patches that differed in the rate at which food pellets were delivered (controlled by fixed‐interval schedules) and in the size of the pellets. The profitability of feeding in each patch was calculated in terms of time (grams per minute) and in terms of effort (grams per bar press). These values were the result of the imposed fixed interval, the size of the pellets, and the rate at which the rats pressed the bar in each condition. The rats ate more food and larger meals, but not more frequent meals, at the patch offering the higher rate of food consumption, calculated as grams per minute. The relative intake at any patch was a function of the relative rate of intake during meals at that patch compared to the other patch. Rats respond to explicit manipulations of feeding time in the same manner as they respond to manipulations of feeding effor

ISSN:0022-5002    

DOI:10.1901/jeab.1991.55-79

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

A successive matching procedure was used to investigate which aspect of the test‐omission procedure is responsible for establishing a postsample stimulus as a cue to forget in pigeons. It was found that a postsample stimulus that reliably followed a sample that was irrelevant to performance functioned as a cue to forget. This result was obtained regardless of whether termination of that postsample stimulus was followed by reinforcement or by the presentation of sample‐independent discriminative stimuli. It was also found that a postsample stimulus that functioned as a cue to forget at the beginning of training lost that function when it was repeatedly presented on trials in which the sample was relevant to performance. These findings reveal that (a) neither a reduction in reinforcement rate nor the omission of the opportunity for discriminated responding is necessary to establish an effective cue to forget and (b) irrelevance of the sample to performance is a sufficient condition to establish a cue to forget. These results suggest that a postsample stimulus that is presented on trials in which remembering the sample is not reinforced differentially will come to set the occasion for not remembering the sam

ISSN:0022-5002    

DOI:10.1901/jeab.1991.55-97

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Four experiments examined the effects of increasing the number of food pellets given to hungry rats for a lever‐press response. On a simple variable‐interval 60‐s schedule, increased number of pellets depressed response rates (Experiment 1). In Experiment 2, the decrease in response rate as a function of increased reinforcement magnitude was demonstrated on a variable‐interval 30‐s schedule, but enhanced rates of response were obtained with the same increase in reinforcement magnitude on a variable‐ratio 30 schedule. In Experiment 3, higher rates of responding were maintained by the component of a concurrent variable‐interval 60‐s variable‐interval 60‐s schedule associated with a higher reinforcement magnitude. In Experiment 4, higher rates of response were produced in the component of a multiple variable‐interval 60‐s variable‐interval 60‐s schedule associated with the higher reinforcement magnitude. It is suggested that on simple schedules greater reinforcer magnitudes shape the reinforced pattern of responding more effectively than do smaller reinforcement magnitudes. This effect is, however, overridden by another process, such a contrast, when two magnitudes are presented within a single session

ISSN:0022-5002    

DOI:10.1901/jeab.1991.55-109

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY