ISSN:0022-5002    

DOI:10.1901/jeab.1988.50-359

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The effects of the risk of electric shock on the meal patterns of rats living in an operant chamber were investigated. Rats could obtain food by working on a response lever that provided reinforcement according to chained fixed‐ratio continuous reinforcement schedules that allowed the animals control over meal size. Using a two‐compartment operant chamber with a safe nesting area and manipulanda area with a grid floor, shock could be correlated with responding on the schedule. Shocks (≥1.25 per hour) were scheduled to occur randomly throughout the day, independent of the rat's behavior. Shock caused a reorganization of meal patterns such that the animals took less frequent but larger meals. This pattern reduced the time the animals spent at risk without compromising caloric balance. Similar changes in feeding pattern were obtained in both hooded and albino rats. Exposure to shock in a separate chamber did not produce these behavioral modifications. The magnitude of shock‐induced alterations of meal patterns was greater with chained fixed‐ratio 90 continuous reinforcement than with chained fixed‐ratio 10 continuous reinforcement. Additionally, the rats seemed to be able to reduce food intake but increase caloric efficiency, such that the reduced food intake did not have deleterious effects on maintenance of body weight. These behavioral modifications reduced the number of shocks received from that which would have been expected if meal pattern changes had not occurred. We suggest that this technique may provide a useful laboratory simulation of the impact that the risk of predation has on foragi

ISSN:0022-5002    

DOI:10.1901/jeab.1988.50-361

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

In two different discrete‐trial procedures, pigeons were faced with choices between fixed‐ratio and progressive‐ratio schedules. The latter schedules entail diminishing returns, a feature analogous to foraging situations in the wild. In the first condition (no reset), subjects chose between a progressive‐ratio schedule that increased in increments of 20 throughout a session and a fixed‐ratio schedule that was constant across blocks of sessions. The size of the fixed ratio was varied parametrically through an ascending and then a descending series. In the reset condition, the same fixed‐ratio values were used, but each selection (and completion) of the fixed ratio reset the progressive‐ratio schedule back to its minimal value. In the no‐reset procedure, the pigeons tended to cease selecting the progressive ratio when it equaled or slightly exceeded the fixed‐ratio value, whereas in reset, they chose the fixed ratio well in advance of that equality point. These results indicate sensitivity to molar as well as to molecular reinforcement rates, and those molar relationships are similar to predictions based on the marginal value theorem of optimal foraging theory (e.g., Charnov, 1976). However, although previous results with monkeys (Hineline&Sodetz, 1987) appeared to minimize responses per reinforcement, the present results corresponded more closely to predictions based on sums‐of‐reciprocals of distance from point of choice to each of the next four reinforcers. Results obtained by Hodos and Trumbule (1967) with chimpanzees in a similar procedure were intermediate between these two relationships. Variability of choices, as well as median choice points, differed between the reset and no‐reset conditions. Although these differences are consistent with the relative costs (in responses per reinforcement) in the two procedures, the differing dispersions of choice probably arise mainly from differing structural constraint

ISSN:0022-5002    

DOI:10.1901/jeab.1988.50-375

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Pigeons responded in a successive‐encounters choice procedure in which accessibility of the less profitable of two outcomes varied either in terms of probability of encounter or search time to encounter (keeping search time to the more profitable outcome constant). When the less profitable outcome was made more probable its acceptance became more likely. However, when search time to encounter the less profitable outcome was shortened, its acceptance became less likely. Both results are consistent with the delay‐reduction hypothesis and with an optimality model developed for application to the successive‐encounters choice proc

ISSN:0022-5002    

DOI:10.1901/jeab.1988.50-395

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The primary goal of this experiment was to determine whether the addition of an operant requirement for access to a less costly (continuous reinforcement) patch of future food increased the time horizon over which that future patch decreased intake in a currently available depleting (progressive‐ratio) patch. Three groups of 4 rats were tested. Each member of the earned‐time group was required to cumulate a fixed‐time outside the progressive‐ratio patch to obtain access to food in the less costly patch; the fixed‐time requirement ranged from 2 to 64 min. Rats in the matched‐time group received response‐independent access to less costly food at the average delay shown by the earned‐time group. Rats in the matched‐time no‐food group were removed from the chamber at the same average delay without receiving access to less costly food. Two of the earned‐time rats showed an increased time horizon relative to that shown by the matched‐time rats (approaching 40 min for 1 rat). The other 2 earned‐time rats markedly increased instrumental responding but showed suppression of intake only when food was less than 20 min away. The matched‐time group showed less suppression of intake over a similar range of delay intervals. Surprisingly, the matched‐time no‐food animals also showed suppression of intake concentrated at the end of the session, possibly reflecting the receipt of their entire daily ration 30 min after the session. The potential importance of time horizons to the foraging process is clear, but experimenters are still working out paradigms for

ISSN:0022-5002    

DOI:10.1901/jeab.1988.50-405

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Laboratory studies of consumer demand theory require assumptions regarding the definition of price in the absence of a medium of exchange (money). In this study we test the proposition that the fundamental dimension of price is a cost‐benefit ratio expressed as the effort expended per unit of food value consumed. Using rats as subjects, we tested the generality of this “unit price” concept by varying four dimensions of price: fixed‐ratio schedule, number of food pellets per fixed‐ratio completion, probability of reinforcement, and response lever weight or effort. Two levels of the last three factors were combined in a 2 × 2 × 2 design giving eight groups. Each group was studied under a series of six FR schedules. Using the nominal values of all factors to determine unit price, we found that grams of food consumed plotted as a function of unit price followed a single demand curve. Similarly, total work output (responses × effort) conformed to a single function when plotted in terms of unit price. These observations provided a template for interpreting the effects of biological factors, such as brain lesions or drugs, that might alter the cost

ISSN:0022-5002    

DOI:10.1901/jeab.1988.50-419

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The pigeon's response to increasing fixed‐ratio schedules in a 24‐hr closed economy is marked by changes in feeding behavior during the daily light phase and by changes in body temperature during the dark phase. The time course of these responses to increasing behavioral cost of obtaining food is very different. Feeding is most affected immediately, within the first day of exposure to moderate fixed ratios. The number of times the pigeons produce the food hopper each day decreases, and the rate at which they eat from the food hopper (grams per minute) when it is available increases, as the fixed ratio is raised. Body temperature is affected later, falling to progressively lower resting levels during the dark phase as body weight drops at the higher fixed ratios when food intake is reduced. The changes in feeding and in body temperature that occur as the fixed‐ratio schedule increases seem to reduce daily energy expenditures, within the constraints imposed by the experiment. The ascending and descending limbs of the bitonic function obtained when total daily operant responding is plotted as a function of fixed‐ratio schedule in the closed economy is possibly related to the occurrence of thermoregulatory strategies for energy conservation. The energetic analysis of performances in the closed economy requires consideration of a variety of energetic strategies available to the species being

ISSN:0022-5002    

DOI:10.1901/jeab.1988.50-441

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Pigeons responded on multiple variable‐interval variable‐interval schedules of reinforcement in an open and a closed economy. Equal duration components were increased in duration while the component rates of reinforcement were held constant, the component schedules were reversed, and component duration was decreased. In the open economy, daily sessions were limited to 1 hr, and subjects were maintained at 80% of their free‐feeding weights through supplemental feeding when necessary in their home cages. In the closed economy, subjects were housed in their experimental chambers and no deprivation regimen was enforced. Relative response rate decreased as components were lengthened in the open economy, whereas in the closed economy relative rate increased as components were lengthened. Response proportions overmatched reinforcer proportions to a greater extent at long component durations in the closed economy, but there was no systematic effect of component duration on responding in the open ec

ISSN:0022-5002    

DOI:10.1901/jeab.1988.50-457

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The present study examined behavioral contrast during concurrent and multiple schedules that provided food and alcohol reinforcers. Concurrent‐schedule contrast occurred in the responding reinforced by food when alcohol reinforcers were removed. It also occurred in the responding reinforced by alcohol when food was removed. Multiple‐schedule contrast appeared for food when alcohol reinforcers were removed, but not for alcohol when food was removed. These results show that behavioral contrast may, but does not always, occur across qualitatively different reinforcers. They also show that multiple‐schedule contrast may be more difficult to produce than concurrent‐schedule contrast. The results have implications for a model of alcohol cons

ISSN:0022-5002    

DOI:10.1901/jeab.1988.50-469

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Learning in a signaled avoidance procedure was studied in the eye withdrawal reflex of the green crab,Carcinus maenas. A puff of air to the eye, which causes eye retraction, was used as the unconditioned stimulus (US). A mild vibration on the carapace, which has no effect on untrained animals, was used as a warning (conditioned) stimulus (CS). Eye withdrawal during the CS led to the omission of the otherwise scheduled US. Acquisition was rapid, reaching about 75% avoidance after 30 trials. Extinction occurred slowly over the course of 40 CS‐only trials. Yoked controls did not perform as well. The behavior of experimental animals in the avoidance procedure was found to be essentially identical to the performance of animals subjected to a classical conditioning paradigm in which CS responses had no effect on US presentation. Additional groups of animals were subjected to experiments in which (a) avoidance conditioning (60 trials) was followed by classical conditioning (40 trials) or (b) classical conditioning was followed by avoidance. The behavior of these groups was, again, essentially identical. The results suggest that there may be an underlying Pavlovian mechanism for the learned response, although the contribution of an operant process is not excluded. The results expand the range of invertebrate animals in which fundamental conditioning phenomena can be demonstrated, and may provide a neuronal model for learning in a signaled avoidance procedur

ISSN:0022-5002    

DOI:10.1901/jeab.1988.50-483

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY