The effects of strong irrelevant thirst on food-rewarded instrumental performance

Abstract

.In Experiment I, rats received one food rewarded trial per day in a runway. One group received all its trials under hunger (Group H); the second group received a random half of its trials under hunger and the other half of its trials under hunger plus thirst (Group H·HT). Group H·HT ultimately ran slower on HT trials than on H trials. In Experiment II, the effects of shifting from H to-HT-and vice versa were examined in a five-phase design. In general, rats run under H ran faster than rats run under HT, and shifts from H to HT produced rapid decreases in speed, while shifts from HT to H produced extremely slow increases in speed. The results of both experiments were interpreted as indicating that the reward value of food is greater under H than under HT and that the manipulation H vs. HT may be viewed as theoretically similar to manipulation of reward magnitude.It has been shown that rats deprived of both food and water (hunger plus thirst, HT) eat less when food alone is given and are inferior in food-rewarded instrumental performance to rats deprived only of food (hunger, H) (e.g., Bolles & Morlock, 1960;Kendler & Law, 1950;Levine, 1956; Verplanck & Hayes, 1953), at least when thirst is strong (22 h deprivation or more). These results may be interpreted as indicating that the reward value of food is less under HT than under H. The purpose of the two experiments reported here was to determine if the effects on performance of manipulating H vs, HT are similar to the effects of manipulating reward magnitude.If the effects on performance of these two manipulations are similar, it would then seem feasible to ask whether or not these similar effects are produced through the same mechanisms.Although the results of previous studies investigating instrumental performance as a function of H vs. HT are compatible with the interpretation that the reward value of food is less under HT than under H, they are also compatible with other interpretations for two reasons. First, previous studies measuring instrumental performance as a function of H vs. HT have employed more than one trial a day. Accordingly, in previous studies, it is possible that HT rats were inferior to H rats because of an aftereffect of having consumed food on Trial I, an aftereffect (e.g., dry mouth) which limited their subsequent food consumption and thus produced slow running. This hypothesis is supported by Bolles and Morlock's (I960) finding that animals run to food under H on some days and under H plus strong T on other days ran equally rapidly under Hand HT on Trial 1 of the day, but ran more slowly under HT than under H on This research was supported in part by Grant MH 23446-01 to the fust author from the National Institute of Mental Health. Experiment II is based in part on a thesis by the third author under the direction of the fust author submitted to the graduate school of Purdue University in partial fulfillment of the requirement for the master's degree. Reprints may be obtained from Elizabeth D. Capaldi, Department of Psychological Sciences...

Pavlovian analysis of interactions between hunger and thirst.

“…The strength of this association is said to govern the vigor of the CR and to be determined in part by the magnitude of the US. Because thirst may reduce the palatability of food (Bolles, 1975;Capaldi et al, 1975), it is possible that the presence of this irrelevant drive will reduce the effectiveness of food as a reinforcer for Pavlovian conditioning. This will result in the growth of a weaker CS-US association in animals with the irrelevant drive than in animals that are only hungry.…”

“…Kendler (1945) found a clear facilitation of extinction in the group with the most severe water deprivation (22 hr) relative to a group that was merely food deprived. Since then, it has been repeatedly found in acquisition that high levels of irrelevant thirst impair instrumental responding for food (Capaldi, Hovancik, & Lamb, 1975) and extinction (e.g., Siegel, 1946) and also that irrelevant hunger is similarly detrimental to water-reinforced responding (e.g., Bolles & Morlock, 1960;Kendler & Law, 1950).Parallel to these instrumental conditioning studies, other authors have noted decreased feeding when water deprivation is imposed on the animal and decreased drinking when food deprivation is in progress (e.g., Toates, 1980; Verplanck & Hayes, 1953). Thus, there appears to be a reciprocally inhibitory relation between the motivational systems underlying behavior directed toward the acquisition and consumption of food and water.…”

Role of incentive learning in reduction of instrumental performance in rats (Rattus norvegicus) by irrelevant drive state

“…Previous studies have suggested that an irrelevant drive state reduces the incentive value of the reinforcer, resulting in impairments of acquisition and expression of instrumental behavior (e.g., Capaldi, Hovancik, & Lamb, 1975;Van Hemel & Myer, 1970). In the present study, we examined whether a devaluation process of a food reinforcer induced by a high level of irrelevant thirst (23.5-h water deprivation) would be dependent on incentive learning; i.e., animals' consummatory contact with a food reinforcer under irrelevant thirst.…”

“…A number of studies have observed decreased feeding when animals are deprived of water (e.g., Rolls & McFarland 1973;Verplanck & Hayes, 1953). Parallel to the consummatory response studies, there is extensive literature reporting that instrumental learning is suppressed by the simultaneous presence of an "irrelevant drive": high levels of irrelevant thirst (22-h or more of water deprivation) impaired acquisition (e.g., Bolles & Morlock, 1960;Capaldi, Hovancik, & Lamb, 1975;Kendler, 1945), and expression (e.g., Siegel, 1946;Van Hemel & Myer, 1970) of food-seeking behavior. These results suggest that the food reinforcer is devalued by irrelevant thirst (Capaldi, Hovancik, & Lamb, 1975;Van Hemel & Myer, 1970).…”

The learned function of food-deprivation cues: A role for conditioned modulation

“…Assuming that water deprivation gives rise to interoceptive stimuli that are different from those produced by food deprivation (cf. Arosel, 1949;Capaldi & Davidson, 1979;Capaldi, Hovancik, & Lamb, 1975;Epstein, 1982;Le Magnen, 1992;Ramachandran & Pearce, 1987), it seems unlikely that discriminative behavior during testing involves control by a configural stimulus that emerges from the combination of food deprivation and contextual cues. There also seems to be no clear a priori basis to assume that stimuli in Context C enter into configural control of responding as the result of simple reinforced training.…”