ISSN:0022-5002    

DOI:10.1901/jeab.1996.65-1

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Four adult humans made repeated choices between two time‐based schedules of points exchangeable for money: a fixed‐interval schedule and a progressive‐interval schedule that began at 0 s and increased in fixed increments following each point delivered by that schedule. Under reset conditions, selection of the fixed schedule not only produced a point but also reset the progressive interval to 0 s. Reset conditions alternated with no‐reset conditions, in which the progressive‐interval duration was independent of fixed‐interval choices. Fixed‐interval duration and progressive‐interval step size were varied independently across conditions. Subjects were exposed to all step sizes in ascending order at a given fixed‐interval value before the value was changed. Switching from the progressive‐interval schedule to the fixed‐interval schedule was systematically related to fixed‐interval duration, particularly under no‐reset conditions. Switching occurred more frequently and earlier in the progressive‐schedule sequence under reset conditions than under no‐reset conditions. Overall, the switching patterns conformed closely to predictions of an optimization account based upon maximization of overall reinforcement density, and did not appear to depend on schedule‐controlled response patterns or on verbal de

ISSN:0022-5002    

DOI:10.1901/jeab.1996.65-5

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Four pigeons responded under autoshaping contingencies in which different conditional stimuli (red or green keylights) were associated with unconditional stimuli of different magnitudes (large or small food pellets) over successive trials within a session. Both topography (beak opening or gape) and strength (rates and latencies of key pecks and gapes) of responding during the conditional stimuli depended on the magnitude of the correlated unconditional stimulus. Key‐peck and gape rates were higher and latencies were shorter in large‐pellet trials than in small‐pellet trials. Gape amplitudes varied directly with pellet size, although conditional and unconditional gapes were larger than either pellet. These findings were replicated when the key colors were presented either on one or two keys and after reversals of the color‐size correlations. Because the unconditional stimulus was varied through pellet size, magnitude was not confounded with food‐access duration or quality. These results demonstrate the effects of the magnitude of the unconditional stimulus, in that rates and latencies of both key pecks (which are directed movements toward the key) and gapes (which are independent of the bird's position and key properties) varied with pellet size. Gape measures were unique in that two dimensions (response strength and topography) of a single response class varied simultaneously with

ISSN:0022-5002    

DOI:10.1901/jeab.1996.65-21

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Four hens worked under independent multiple concurrent variable‐interval schedules with an overlaid aversive stimulus (sound of hens in a poultry shed at 100dBA) activated by the first peck on a key. The sound remained on until a response was made on the other key. The key that activated the sound in each component was varied over a series of conditions. When the sound was activated by the left (or right) key in one component, it was activated by the right (or left) key in the other component. Bias was examined under a range of different variable‐interval schedules, and the applicability of the generalized matching law was examined. It was found that the hens' behavior was biased away from the sound independently of the schedule in effect and that this bias could be quantified using a modified version of the generalized matching law. Behavior during the changeover delays was not affected by the presence of the noise or by changes in reinforcement rate, even though the total response measures were. Insensitivity shown during the delay suggests that behavior after the changeover delay may be more appropriate as a measure of preference (or aversiveness) of stimuli than are overall behavior measu

ISSN:0022-5002    

DOI:10.1901/jeab.1996.65-37

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Performance of dairy cows responding under concurrent variable‐interval variable‐interval schedules of food delivery was examined, with results analyzed in terms of the generalized matching equation. In Experiment 1, bias measures indicated that crushed barley was preferred over meatmeal when these foods were available under the alternative schedules. For whole‐session data, substantial undermatching of response and time‐allocation ratios to obtained reinforcement ratios was evident. Postreinforcement pause time ratios approximately matched obtained reinforcement rates. Subtracting these times from total time‐allocation values yielded net time‐allocation ratios that undermatched obtained reinforcement ratios to a greater degree than did whole‐session time‐allocation ratios. In Experiment 2, substantial undermatching was evident when the same foods (hay for 2 cows, crushed barley for 2 others) were available under the alternative schedules. Food‐related activities and other defined behavior not related to food were quantified by direct observation, and were found to occupy a substantial proportion (roughly 40% to 80%) of experimental sessions. Subtracting the time spent in these activities from the time allocated to each component schedule did not reduce the degree of undermatching obtained. Across all conditions in both experiments, slopes of regression lines relating behavioral outputs to environmental inputs characteristically were below 0.6, which agrees with prior findings and suggests that, contrary to suggestions in the literature, undermatching in dairy cows is not the result of using different foods under alternative schedules or differential pausing unde

ISSN:0022-5002    

DOI:10.1901/jeab.1996.65-57

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Eight pigeons were trained on a delayed presence‐versus‐absence discrimination paradigm in which a sample stimulus was presented on some trials but not on others. If a sample was presented, then a response to one choice key produced food. If no sample was presented, a response to the other choice key produced food. The basic finding was that performance remained constant and well above 50% correct on no‐sample trials as the retention interval increased, whereas performance dropped precipitously (to below 50% correct) on sample trials. In the second phase of the experiment, all of the trials were no‐sample trials, and reinforcers were delivered probabilistically for one group of pigeons and according to time‐based schedules for the other group. The exact reinforcement probabilities used in Phase 2 were those calculated to be in effect on no‐sample trials in Phase 1 (according to a discrete‐state model of performance). Subjects did not show exclusive preference for the richer alternative on no‐sample trials in the first phase, but those in the probabilistic group developed near‐exclusive preference for the richer alternative during the second phase. These data are inconsistent with the predictions of the discrete‐state model, but are easily accommodated by an account based on signal detection theory, which also can be applied effectively to discrimination of event duration and the “subjecti

ISSN:0022-5002    

DOI:10.1901/jeab.1996.65-81

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Key pecking by pigeons was maintained on a chained fixed‐interval 4‐min (12‐min for 1 subject) fixed‐ratio 1 schedule of food presentation. Attacks toward a restrained and protected conspecific were recorded. In the first experiment, the amount of food presented per interval was manipulated across phases by varying the number of fixed ratios required in the terminal link of the chain. Measures of attack for all pigeons during the fixed‐interval component increased monotonically as a function of food amount. In the second experiment, two different food amounts alternated within each experimental session under a multiple schedule. For both pigeons in this experiment, measures of attack were higher during the component that delivered the larger food amount per interval. The differences in levels of attack induced by the two food amounts in Experiment 2, however, were not as great as in Experiment 1; apparently this was because attack during the first interval of each component was controlled in part (P‐5626) or entirely (P‐7848) by the reinforcement amount delivered at the end of the previous component. Attack was also a function of the location of the interfood interval within the session. For both pigeons, attack tended to decrease throughout the session. The results of both experiments suggest that attack is an increasing function of reinforcement amount under fixed‐interval schedules, but that this function may be influenced by the manner in which reinforcement amount is manipulated, by the duration of the interfood interval, and by the location of the interfood interval within the experimental session. In general, these results are compatible with theories of induced attack and other schedule‐induced behavior that emphasize aversive aftereffects of reinforce

ISSN:0022-5002    

DOI:10.1901/jeab.1996.65-93

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Three pigeons responded for food reinforcement on multiple variable‐interval schedules in which the total consumption of food was entirely determined by the subjects' interaction with the schedules (a closed economy). The finding of overmatching, where response allocation between components is more extreme than the distribution of reinforcers, was reconfirmed. Generalized‐matching sensitivity decreased from overmatching to undermatching values typical of conventional multiple schedules when food deprivation was increased by decreasing session duration, but not when deprivation was increased by decreasing overall reinforcer rate. Sensitivity also increased from undermatching to overmatching as session duration increased from 100 min to 24 hr, while deprivation was held constant by decreasing overall reinforcer rate. These results can be understood in terms of increases in the value of extraneous reinforcers relative to food reinforcers as deprivation decreases or as the economy for extraneous reinforcers becomes more closed. However, no published quantitative expression of the effects of extraneous reinforcers is entirely consistent with the resu

ISSN:0022-5002    

DOI:10.1901/jeab.1996.65-111

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The spontaneously hypertensive rat (SHR) may model aspects of human attention deficit hyperactivity disorder (ADHD). For example, just as responses by children with ADHD tend to be variable, so too SHRs often respond more variably than do Wistar‐Kyoto (WKY) control rats. The present study asked whether behavioral variability in the SHR strain is influenced by rearing environment, a question related to hypotheses concerning the etiology of human ADHD. Some rats from each strain were reared in an enriched environment (housed socially), and others were reared in an impoverished environment (housed in isolation). Four groups—enriched SHR, impoverished SHR, enriched WKY, and impoverished WKY—were studied under two reinforcement contingencies, one in which reinforcement was independent of response variability and the other in which reinforcement depended upon high variability. The main finding was that rearing environment did not influence response variability (enriched and impoverished subjects responded similarly throughout). However, rearing environment affected body weight (enriched subjects weighed more than impoverished subjects) and response rate (impoverished subjects generally responded faster than enriched subjects). In addition, SHRs tended to respond variably throughout the experiment, whereas WKYs were more sensitive to the variability contingencies. Thus, behavioral variability was affected by genetic strain and by reinforcement contingency but not by the environment in which the subjects were r

ISSN:0022-5002    

DOI:10.1901/jeab.1996.65-129

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Key pecking by 6 pigeons was maintained by a fixed‐ratio 30 schedule of food presentation while body weights were 80% of free‐feeding weights. Acute administration of cocaine (0.3 to 13.0 mg/kg, i.m.) dose‐dependently decreased response rates. Dose‐effect curves were shifted to the right when 3 of the 6 pigeons were maintained at 70% of free‐feeding weights and were shifted to the left when the other 3 pigeons were maintained at 90% of free‐feeding weights. Then a dose of cocaine that initially decreased response rates by more than 95% of control rates was administered before each daily session. Comparable degrees of tolerance to these rate‐decreasing effects developed in the two groups. The rate at which responding recovered was relatively rapid for pigeons in the 70% free‐feeding‐weight group and was slower for 2 of the 3 pigeons in the 90% free‐feeding‐weight group. When body weights were then increased from 70% to 80% or were decreased from 90% to 80% of free‐feeding weight, performance was disrupted initially only for pigeons whose weight went from 70% to 80% of free feeding. In the present experiment the degree of deprivation may have indirectly influenced the degree of tolerance that developed to cocaine's response rate‐decreasing effects because it directly influenced the dose chosen to be administered chronically. The degree of deprivation appeared to have a more direct influence on the rate at

ISSN:0022-5002    

DOI:10.1901/jeab.1996.65-145

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY