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981.
982.
983.
Rats were given backward pairings of a tone (CS) and shock (US) and were then tested for response to the CS in a lick suppression test. Animals given a cuing or reminder treatment prior to the test exhibited enhanced suppression in the presence of the tone relative to a variety of control conditions. The cue-induced suppression enhancement did not appear to result from sensitization or short-term motivational changes nor did it seem to depend on second-order conditioning of the test context. The effect appeared more robust as the number of backward conditioning trials preceding the cue increased. The results were discussed in terms of current explanations of backward conditioning effects.  相似文献   
984.
Handling time and choice in pigeons   总被引:2,自引:1,他引:1       下载免费PDF全文
According to optimal foraging theory, animals should prefer food items with the highest ratios of energy intake to handling time. When single items have negligible handling times, one large item should be preferred to a collection of small ones of equivalent total weight. However, when pigeons were offered such a choice on equal concurrent variable-interval schedules in a shuttlebox, they preferred the side offering many small items per reinforcement to that offering one or a few relatively large items. This preference was still evident on concurrent fixed-cumulative-duration schedules in which choosing the alternative with longer handling time substantially lowered the rate of food intake.  相似文献   
985.
Distributions of reinforcers between two components of multiple variable-interval schedules were varied over a number of conditions. Sensitivity to reinforcement, measured by the exponent of the power function relating ratios of responses in the two components to ratios of reinforcers obtained in the components, did not differ between conditions with 15-s or 60-s component durations. The failure to demonstrate the “short-component effect,” where sensitivity is high for short components, was consistent with reanalysis of previous data. With 60-s components, sensitivity to reinforcement decreased systematically with time since component alternation, and was higher in the first 15-s subinterval of the 60-s component than for the component whose total duration was 15 s. Varying component duration and sampling behavior at different times since component transition may not be equivalent ways of examining the effects of average temporal distance between components.  相似文献   
986.
Two experiments examined pigeons' response rates during short trials signaled by stimuli closely spaced along a wavelength continuum. In Experiment 1 separate halves of the continuum were correlated with different reinforcement schedules. In Experiment 2, the middle stimulus was accompanied by a lower probability of reinforcement than were the remaining wavelengths. Both procedures resulted in dimensional contrast “shoulders,” seen as relatively enhanced or depressed response rates in the presence of stimuli between the extreme of the continuum and the border separating the positive and negative stimuli. Sequential analyses addressed possible contributions of the following interactions: (a) local contrast, seen when rate during a given schedule depends on the schedule in the just-preceding trial; (b) modification of local contrast by the similarity of the signaling stimuli (P. Blough, 1983); and (c) schedule-independent rate contrast, seen when rate in a given trial depends on the rate controlled by the stimulus that accompanied the just-preceding trial (Malone & Rowe, 1981). Dimensional contrast functions were similar when isolated according to the schedule, to the similarity of the signaling stimulus, and to the response rate of the just-preceding trial. The interactions noted above do not appear to make important contributions to this effect.  相似文献   
987.
988.
Howard S. Liddell, Professor of Psychobiology in the Department of Psychology at Cornell University, was one of the earliest American students and developers of I.P. Pavlov's theory of the conditioned reflex and an early researcher on stress. The significance of Liddell's work on stress was fully recognized when he was sent, as a member of a commission, to the battlefront at the height of the Korean War to study stress and self-control in the soldiers. This profound experience convinced Liddell that behavioral research must ultimately be made relevant to the understanding and elevation of human behavior. He spent the remaining ten years of his life in efforts to implement this conviction through research, writing, and lectures before scientific and lay groups.  相似文献   
989.
There appears to be an association between a "global" mode of perceptual processing and a cluster of personality traits, one of which is impulsivity. The goal of the present study was to clarify this relationship. Subjects differing in impulsivity (as measured by a self-report inventory) performed speeded cardsorting tasks. They sorted stimuli consisting of large letters made up of smaller letters. Highly impulsive subjects had no more difficulty than other subjects in ignoring the large, "global," letters when they tried to attend to the smaller, "local," letters of which they were composed, nor were they more vulnerable than other subjects to Stroop-like response interference produced by the global letters. High impulsives did have particular difficulty when the task required that they integrate the information provided by the local and global letters. This finding can be explained in terms of individual differences in the value placed on speed relative to accuracy in information processing.  相似文献   
990.
Scores on the Beck Depression Inventory (BDI) were periodically obtained from the roommates of college students who exhibited a persistent mild depression over a 3-month period. For comparative purposes, BDI scores were also obtained from roommates of individuals who were transiently depressed and from subjects with nondepressed roommates. In comparison with control subjects, the roommates of persistently depressed persons displayed a progressive increase in BDI score over the course of the study.  相似文献   
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