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1.
In a series of three experiments, rats shifted from a 32% to a 4% sucrose solution, after 10 days’ exposure to the 32% solution, exhibited a negative contrast effect in lick rate. In each experiment, shifted rats that received a novel stimulus (tone) during the postshift period exhibited a higher lick rate (smaller contrast effect) than shifted subjects not receiving the tone. This increase in lick rate resembles Pavlovian disinhibition and is interpreted as supporting an inhibitory view of successive negative contrast effects. Control conditions included in Experiments 2 and 3 favored the disinhibition interpretation of the effect of the tone, as opposed to a rate-dependency hypothesis or to the nonspecific energization of behavior. In Experiments 4–6, the tone was introduced coincident with the occurrence of a simultaneous negative contrast effect. Rather than disinhibition, a decrease in licking occurred. These results were discussed in terms of differences between successive and simultaneous contrast. 相似文献
2.
Rats were shifted from 32% sucrose solution in one apparatus to a 4% sucrose solution in a different apparatus, and the performance of these animals was compared to rats that received the 4% solution in both situations. Transsituational negative contrast effects were found in both consummatory and instrumental measures of behavior and, in addition, these contrast effects were found to have some elements in common with both successive and simultaneous contrast effects, but were identical to neither. 相似文献
3.
Reactivity to a reward is affected by prior experience with the different reinforcer values of that reward, a phenomenon known as incentive relativity, which can be studied using the consummatory succesive negative contrast (cSNC) paradigm, in which the performance of animals that receive a 4 % sucrose solution after trials on which they were exposed to 32 % sucrose is compared with that of subjects that always receive the 4 % sucrose solution. The exploration of a novel open field can enhance or block the acquisition of associative and nonassociative memories. The effect of open field on cSNC has not yet been explored. The main result of the present study was that open-field exposure significantly modified the expression of cSNC. Exposure to an open field 1 h but not immediately before the downshift interfered with the expression of cSNC. These animals drank more of the downshifted reward than did controls that were not exposed to the apparatus, and this behavior persisted for up to three recovery trials. This phenomenon was observed even when the animals were given a more protracted preshift phase and when the discrepancy between the preshift and shift incentive values of sucrose were increased. An open field also interfered with incentive downshift when open-field exposure occurred 6 h before the downshift, and repeated exposure to the apparatus did not deteriorate this effect. The present study adds to a growing body of literature that indicates that open-field exploration can interfere with memory formation. 相似文献
4.
Charles F. Flaherty 《Learning & behavior》1982,10(4):409-440
The literature relevant to incentive contrast effects is reviewed, with emphasis on the data published since the reviews by Black (1968) and Dunham (1968). Contrary to the evidence available for the earlier reviews, the current literature indicates that positive contrast is a reliable phenomenon. Its occurrence is facilitated by use of a constant delay of reward, use of a long runway, or possibly by a shift while a negative contrast effect, resulting from a previous shift, is still present in the animals’ behavior. Positive contrast also occurs in consummatory behavior when sucrose or saccharin solutions are shifted. Conditions that are ineffective in producing positive contrast are reviewed, as are the effects of numerous variables on both successive and simultaneous contrast. In addition, positive and negative contrast effects resulting from shifts in delay or percentage of reward, contrast resulting from shifts in sucrose, saccharin, or ethanol solutions, contrast in choice behavior, and transsituational contrast are reviewed. The relationship of the data to several theoretical interpretations of contrast is also considered. 相似文献
5.
Rats shifted from 32% sucrose to 4% sucrose lick less than rats that experience oniy the 4% solution. Previous experiments have found this negative contrast effect to be reduced (“disinhibited”) by the addition of a novel tone in the postshift period. In Experiment 1 of this paper, the negative contrast effect was enhanced when a novel flavor was added to the sucrose solution in the postshift period. In Experiments 2–4, changes in the ambient context, even changes sufficient to produce disruptions in licking, did not alter the degree of negative contrast. Tiese results suggest that (1) rats compare rewards across substantially different contexts, (2) contrast may serve to enhance taste neophobia, and (3) a disinhibitory effect may be confined to the presentation of punctate, nontaste, novel stimuli within a familiar context. 相似文献
6.
Bruce R. Lombardi 《Learning & behavior》1980,8(4):617-620
In two experiments, a successive negative contrast effect in licking was produced by shifting rats from 32% to 4% sucrose solution. Subsequent to the downshift in reward, the rats were tested for licking either a plain 12% sucrose solution or 12% plus a neutral flavor. Licking for the 12% solution was depressed in downshifted rats when a flavor was present, regardless of whether this flavor was novel or had been present in the shift solution. The results were interpreted in terms of an enhancement of neophobia by reward reduction. 相似文献
7.
An animal’s appetitive behavior is not a fixed response to current stimulation but can be affected by the anticipation of future events. For example, rats regularly given access to a moderately valued solution followed by a higher value solution (e.g., 4 % sucrose → 32 % sucrose) consume less of the initial solution than in control conditions where the initial solution is not followed by a higher value solution (e.g., 4 % sucrose → 4 % sucrose). Previous analyses have suggested that this negative anticipatory contrast effect does not depend on the “expectation” of a valuable stimulus producing a functional devaluation of a currently available stimulus of lesser value. In a within-subjects anticipatory contrast procedure, this study revealed that both consumption and the mean size of licking clusters were smaller for a 4 % sucrose solution on days when it preceded 32 % sucrose than on days when 4 % preceded 4 %. Since lick cluster size typically bears a positive monotonic relationship with the concentration of palatable solutions, this reduction is indicative of a decrease in the palatability/hedonic value of the solution subject to contrast. As such, we provide direct evidence that negative anticipatory contrast does produce a functional devaluation of the solution, thus challenging prevailing theoretical assumptions. 相似文献
8.
Contrast in consummatory behavior was investigated following repeated shifts from 32% to 4% sucrose. In Experiment 1, contrast in licking and in open-field measures of activity occurred following the second and third downshifts. In Experiments 2a and 2b, equivalent contrast effects occurred following the first and second downshifts in sucrose. In Experiment 3, negative contrast remained unabated following nine downshifts in animals shifted between 32% and 4% sucrose on alternate days. Similar results were found for five downshifts in animals shifted every 2 days. In both of these latter conditions, positive contrast occurred over the first few shifts and was then lost as the 32% control group reached asymptote. These data show that repeated negative contrast effects in consummatory behavior are robust and enduring and occur under several different sets of experimental parameters. The results are discussed in terms of reinforcement level and emotional interpretations of contrast effects, and the possibility was suggested that the causal mechanism of contrast changes with repeated shifts. 相似文献
9.
In three experiments, rats shifted from 32% to 4% sucrose consumed less of the 4% sucrose than did rats that had received only the 4% solution. Experiment 1 showed that this negative contrast effect was not accompanied by a corticosterone elevation on the first day subsequent to the shift. Experiments 2 and 2a showed that corticosterone levels were substantially elevated on the 2nd postshift day and that there was a tendency for degree of elevation in corticosterone to be related to degree of lick suppression. These results are discussed in terms of other data suggesting that anxiolytic drugs and disinhibitory stimuli are more effective in alleviating contrast on the 2nd postshift day than on the 1st postshift day. It is suggested that, in the present paradigm, reaction to stimulus change may be the primary determinant of contrast on the 1st postshift day, but emotional processes related to reward loss and/or conflict develop by the 2nd postshift day. 相似文献
10.
In three experiments, the time horizon over which the rat evaluates alternative feeding sources was investigated. The time horizon was measured by the suppression of intake of one incentive (a 0.15% saccharin solution) when a preferred alternative incentive (a 32% sucrose solution) was available but delayed. In Experiment 1, we found a direct function between the amount of saccharin intake and the delay time before access to 32% sucrose. Compared with intake for a saccharin-only control, saccharin intake was suppressed before 4-min and 16-min sucrose delays, but not before a 32-min delay. Because previous work (Flaherty & Checke, 1982) had reported suppression before a delay of nearly 32 min, in the subsequent experiments we examined factors that might account for this difference. In Experiment 2, we found that saccharin intake was suppressed before a 32-min delay interval when saccharin and sucrose solutions were presented in a bright-novel test environment but not when the same solutions were presented in the home cage. In Experiment 3, we found that the time between testing and subsequent postsession feeding could also affect the suppression of saccharin intake. Saccharin intake was suppressed when access to 32% sucrose was delayed by 32 min and the test situation was followed by immediate postsession feeding, but not when postsession feeding was delayed by 90 min. These results thus extend estimates of the rat’s time horizon to at least 32 min, but indicate that the effective time horizon can vary, depending on the test situation. 相似文献
11.
Previous experiments have shown that the negative contrast effect in consummatory behavior that occurs when rats are shifted from 32% to 4% sucrose is alleviated by the tranquilizer chlordiazepoxide (CDP). However, in these experiments, CDP was effective on the second postshift day but not on the first postshift day. The three experiments described in this paper suggest that this differential effectiveness of CDP is not due to the difference in preshift-postshift retention intervals on Day 1 (24 h) and Day 2 (48 h), but is due instead to the necessity of some degree of experience (about 5 min) with the postshift solution. These results, combined with those of an earlier study which showed elevated corticosterone in shifted animals on the second postshift day but not on the first postshift day, suggest that negative contrast may be a dynamic process, involving sequential processes of detection, evaluation, and conflict over the postshift period. It was further suggested that CDP becomes effective in moderating contrast only when the conflict stage is reached. 相似文献
12.
Qualitatively different reinforcers and parameters of Herrnstein’s (1970) response-strength equation
Terry W. Belke 《Learning & behavior》1998,26(3):235-242
Previous research that compared the estimated parameters (i.e.,k andR e) from Herrnstein’s (1970) hyperbolic matching law equation within the same individuals responding for qualitatively different consummatory reinforcers (i.e., water and sucrose solution) found similar asymptotic response rates (k). The present study compared these parameters within subjects responding on levers for consummatory and nonconsummatory reinforcers. Male Wistar rats responded on a lever in a running wheel on a series of tandem FR 1 VI schedules for either 0.1 ml of a 15% sucrose solution or the opportunity to run for 15 sec. Herrnstein’s hyperbola was fit to response and reinforcement rates from each session. Results showed thatk values were significantly higher for sucrose than for wheel-running reinforcement. On average,R e was lower for sucrose than for wheel-running reinforcement, though not significantly lower. The results of the present study appear to violate the assumption of the constancy ofk in Herrnstein’s matching law analysis. 相似文献
13.
Only a limited number of species have been found capable of generalized matching-to-sample (MTS) after exposure to relatively few training exemplars. We trained a juvenile, experimentally naive California sea lion (Zalophus californianus) in MTS, using a pair of three-dimensional objects as samples. Successful matching to a criterion of 90% correct or better over 2 successive sessions was attained in 12 sessions (269 trials and 70 errors). Two subsequent “partial” transfer tests, in which each of the two training objects was paired with a novel test object, and four additional transfer tests, all with novel objects, were presented following training. An 80% performance criterion over 2 successive sessions was reached, or closely approximated, in from 2 to 4 transfer sessions for all transfer tests; errors to criterion tended to be reduced across the successive novel transfer tests and were as few as five during the final two tests; and performance on the first 48 trials of the last two novel transfers was not significantly different from a near-ceiling level baseline performance measure. Neophobic responses of the sea lion to new objects precluded an unbiased evaluation of immediate (Trial 1) transfer. The sea lion’s short-term memory for sample objects was also measured. Matching performance was maintained at a level of 78% correct responses or better for delays through to 45 sec after removal of the sample object. At a 58-sec delay, the longest tested, performance declined to 69% correct responses. These retention levels are only somewhat below levels reported for dolphins and nonhuman primates tested on visual delayed MTS, but they are above levels typically reported for pigeon subjects. 相似文献
14.
Rats were given alternating 1-min access to two tubes containing sucrose solutions that varied in concentraton (32% vs. 2%, 32% vs. 4%, 32% vs. 8%, and 32% vs. 16%). Lick rate for 32% sucrose was higher when the alternative tube contained a lower concentration solution than when both tubes contained 32% (a positive-contrast effect), and lick rate for the lower concentration solution (2%, 4%, 8%, or 16%) was lower when the alternative tube contained 32% than when both tubes contained the lower concentration solution (negative contrast effect). Proportion of licks made for 32% under contrast conditions tended to match the proportion of concentration available from that tube. Regression analysis of the ratio of licks made to the two tubes under contrast conditions as a function of ratio of concentrations available indicated a good fit to a power function with an exponent of 1.13, within the range of those typically found in human magnitude estimation studies of relative sweetness. 相似文献
15.
The role of incentive learning in instrumental performance following an upshift in the degree of water deprivation was analyzed in three experiments. In Experiments 1A and 1B, rats trained to perform an instrumental action reinforced by either sucrose or maltodextrin solutions when in a low-deprivation state were shifted to a high-deprivation state and tested in extinction. This shift in water deprivation increased performance only if the animals had been exposed to the reinforcer in the high-deprivation state prior to testing. In Experiment 2, the role of the instrumental contingency in mediating the preexposure effect observed in the first two studies was examined by training rats to make two instrumental actions for different outcomes. The preexposure experience with the outcomes produced a relative increase in performance of the action reinforced with the incentive preexposed in the high-deprivation state when a choice between the two response alternatives was conducted in that state. These experiments support the conclusion that instrumental performance following revaluation of the reinforcer by an upshift in the level of thirst depends on a process of incentive learning. 相似文献
16.
Handling of preweanlings (Days 2–15) had substantial effects on the open-field behavior of rats when tested as adults. In general, handled rats reared more, ambulated more, and defecated less than nonhandled rats. However, the handling manipulation had no effect on the degree of negative contrast that occurred when rats were shifted from 32% to 4% sucrose. Experiments 2 and 3 showed that preweaning handling did not influence sucrose neophobia in two different test situations. These data, in conjunction with those of other studies, suggest that preweaning handling may have powerful but limited effects on adult behavior, and that these effects are probably not best characterized in terms of global concepts such as emotionality. 相似文献
17.
Previous experiments have shown that the intake of a 0.15% saccharin solution is suppressed if saccharin access is followed by access to 32 % sucrose in brief daily pairings. The present experiments found that: (1) the degree of suppression was not altered when no time elapsed between presentation of the two solutions each day (15 sec had been the minimum in previous experiments and was used as the control in this experiment); (2) the degree of suppression was not altered by chlordiazepoxide (6, 12, or 20 mg/kg), although the drug had large appetite-stimulating effects; (3) suppression was not influenced by amphetamine (0.25 or 0.50 mg/kg); and (4) contrast could be established or eliminated, even after extended training, by manipulating the sequences of solutions presented (saccharin-saccharin or saccharin-sucrose). The results were interpreted in terms of a contrast effect based on the learned anticipation of a preferred substance. The chlordiazepoxide data suggest that this contrast is different from successive negative contrast, and the intersolution interval data suggest that the occurrence of contrast rather than a reinforcement effect is not due to a time gap between presentations of the two solutions. 相似文献
18.
Sequence learning in pigeons was studied in asimultaneous chaining paradigm: all stimuli and the opportunity to respond to each stimulus were available simultaneously. In contrast to the traditionalsuccessive chaining paradigm, a simultaneous chaining paradigm provides no differential feedback following each response (except the last). Subjects were first trained to perform on sequences of two (AB), then three (ABC), and then four colors (ABCD). Performance greatly exceeded that predicted by models of random choice. Generalization to novel arrays of three and four colors was complete. After training with a four-color sequence, the subjects were tested with subsequences consisting of all possible combinations of two and three of the four training colors (e.g., BD, AD, BC, ACD, BCD, etc.). The successful completion of these subsequences showed that the organization of the original sequence did not entail overt pecks to successive elements of that sequence. That subjects can respond accurately on nonadjacent subsets is not readily explained by a chaining theory, or by any theory that assumes that responding to element n provides a cue for responding to element n+1. 相似文献
19.
Hungry rats were trained to perform two instrumental actions, one for salt- and the other for lemonflavored polycose solution. When they were sated on one of these two outcomes by prefeeding immediately prior to a choice extinction test, the action trained with the prefed solution was performed less than the other action. The subsequent experiments examined the role of incentive learning in this specific satiety-induced outcome revaluation effect. The second experiment demonstrated that the experience of consuming a flavored polycose solution to satiety enabled the state induced by polycose consumption to control the devaluation of the flavored outcome. By contrast, the third study found that, although devaluing the prefed outcome, specific-satiety treatments could induce a relative inflation in the incentive value of other food outcomes. The final two studies demonstrated an increased outcome-devaluation effect in instrumental performance when these devaluation and revaluation effects were combined. Taken together, these studies demonstrate that specific satiety treatments produce changes in outcome value that depend upon incentive learning. 相似文献
20.
R. A. Burns 《Learning & behavior》1976,4(4):473-479
Two experiments assessed the role of aftereffect learning in rats rewarded with sucrose solutions. In Experiment 1, rats were trained in a single straight runway for two trials on each of 18 days, each trial terminating with either large (20% scurose) or small (3% sucrose) reward. The ITI was 3–5 min. The sequence of daily rewards for each of four groups was small-small (SS), small-large, (SL), large-small (LS), or large-large (LL). Response patterning and a simultaneous negative contrast effect were observed in LS and SL relative to the consistently rewarded controls. During 10 massed extinction trials, resistance to extinction was greatest for Group SL, followed in order by Groups SS, LL, and LS. Experiment 2 examined single alternation of large and small rewards administered for 10 trials on each of 31 days with an ITI of 60 sec. Reward for one group was 20% or 3% sucrose while another received 1 or 10 45-mg Noyes pellets. Appropriate patterning developed only in the food-pellet rewarded animals. The overall results suggest that sucrose rewards may produce high-amplitude and long-duration aftereffects which interfere with learning in designs employing several massed daily trials, but which may facilitate learning—relative to food-pellet rewards—with longer intertrial intervals and fewer daily trials. 相似文献