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Shock

Fig. 5.3. This Garcia and Koelling (1966) study demonstrates the principle of selective association. The animals studied selectively associated nausea with sweetness and shock with auditory and visual stimuli, but not vice versa.

(1971), who compared the differential acquisition of taste aversion in rats and quail. The subjects were variously presented with water having a sour taste, water colored dark blue, or water that was both sour and dark blue. Rats experiencing nausea after drinking these combinations of color and flavor responded to flavor cues but not visual cues. Quail, on the other hand, were able to associate either the color or the taste of the water with nausea, provided the cues were presented separately; however, if both taste and color were presented together, the color cue overshadowed the flavor cue. When later offered sour or colored water, the quail drank sour water but not colored water. An obvious conclusion to be drawn from this experiment is that quail are prepared to make the taste-aversion association more effectively through the modality of sight than taste, whereas rats are better prepared to acquire a taste aversion through the modality of gustation only.

Many animal species are programmed to wait for some fixed period after ingesting a new food item in order to determine whether it is toxic to them (Gould, 1982). A blue jay, for example, hunts and eats butterflies, but if it happens to eat a monarch butterfly, it will soon become ill and vomit. Illness is induced by cardiac glycosides stored in various parts of the butterfly's body. These substances are obtained by the butterfly larva feeding on the milkweed. After a single exposure to the nausea-producing monarch butterfly, a blue jay will avoid hunting them in the future (Brower, 1969). The most significant avoidance cue for blue jays is the butterfly's colorful wing pattern. Interestingly, the monarch butterfly's wing color and pattern has been mimicked by other butterflies (most notably, the viceroy butterfly), ostensibly providing them with safety from previously "trained" blue jays. Gould (1982) contends that taste aversion or "rapid food-avoidance conditioning" is a widely distributed form of programmed learning in the animal world. Each species is responsive to a specific set of cues that identify the most salient feature or sign stimulus associated with the evocation of illness. Tinbergen describes other cases involving learned food avoidance and mimicry. Songbirds exhibit a learned avoidance toward wasps due to illness induced by eating them:

When a songbird such as a Redstart meets with a wasp for the first time in its life, it captures it. Sometimes, but that is relatively rare, the wasp will manage to sting the bird. The bird then lets go, and may show in various ways that the sting affected it rather unpleasantly; it may shake its head, and wipe its bill. Anyway it shows no further interest in the wasp. Usually however the wasp does not sting, it is killed before it can do so. Then it becomes evident that a wasp is distasteful: the bird does not finish it, and if it is eaten, it is often brought up again afterwards. Mostler has shown that most songbirds learn from one or a few such experiences to leave wasps alone. That they recognize such unpalatable insects by their colours is evident from the fact that from then on such a bird avoids not only wasps, but all similarly coloured insects. (1953/1975:95-96)

Many birds exhibit a similar avoidance toward the caterpillar of the cinnabar moth. After a single ingestion, birds learn to refuse all larvae with the caterpillar's distinctive black-and-yellow pattern of marking.

Studies with wild canids have demonstrated that taste aversion can be effectively employed to deter appetitive interest toward highly desirable prey animals. Coyotes have been conditioned to avoid sheep after being exposed to mutton and wool tainted with lithium chloride (LiCl) (Gustavson et al., 1974). Presumably, these treated coyotes had some previous safe exposure to the prey in the past. Besides coyotes, many other animals have shown a similar response to the tasteaversion procedure (Garcia et al., 1977; Gustavson, 1977). Mugford (1977) demonstrated that a strong taste aversion toward a highly palatable food item could be produced in cats if ingestion of the food was followed by treatment with LiCl. Gustavson and Gustavson (1982) compared the suppressive effects of peripheral versus internal aversive stimuli (nausea) presented at different points during the feeding sequence—that is, while rats approached or after they had consumed a highly desirable food item (an Oreo cookie). The peripheral stimuli included shock and repellents (ammonia, mustard, and quinine). Nausea produced by LiCl injections provided the internal aversive stimulation (taste aversion). They examined the suppressive effects of these aversives across three contexts: treatment cage, home cage, and novel cage (Table 5.1). Only taste aversion was shown to in crease the latency of approach in all three training situations but only if the rats had consumed some of the cookie prior to the induction of nausea. Rats shocked as they approached the cookie exhibited significant hesitation when later tested in the treatment cage, but showed little evidence of transfer of suppression when tested in the home-cage and novel-cage situations. interestingly, consumption measures indicated that rats exposed to quinine and mustard ate more of the cookie when it was presented in the home cage. Rats exposed to ammonia while they were eating exhibited significantly more hesitation when given a cookie in the novel test situation. A similar suppressive effect in the novel situation was not produced by quinine or mustard. in general, these findings suggest that aversion training using peripheral stimulation tends to be more context specific, whereas flavor-associated aversive internal stimulation (nausea) has cross-contextual implications: the suppression of appetitive and consummatory behavior. The authors illustrate the effect:

Table 5.1. Comparison of peripheral versus internal aversive conditioning

Training phase

Approach Group-

—Aversive stimulation presented

as the animal approached the cookie

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