Two experiments investigated variables influencing the acquisition of a conditioned aversion in juvenile and adult rats. In the first experiment, juvenile and adult subjects received six scopolamine-illness pairings utilizing a forced single-bottle measurement technique. Whereas adult rats learned an aversion to sucrose more rapidly when sucrose was novel rather than familiar, neither familiarized nor novel juvenile animals exhibited any aversion to sucrose. The second experiment compared acquisition of a taste aversion in juvenile and adult animals with either a one-bottle forced technique or a two-bottle choice procedure. Adult rats acquired an aversion to sucrose associated with LiCI illness more rapidly with a two-bottle than with a one-bottle measurement technique, although a strong sucrose aversion was seen in adult rats after four sucrose-illness pairings with the one-bottle technique. Young juvenile rats avoided sucrose when a two-bottle free-choice procedure was employed, while showing only a weak aversion to sucrose with the forced technique after four pairings. These results show that young animals can learn to avoid a taste associated with illness if the appropriate conditions are employed.Animals readily avoid a taste stimulus paired with illness (e.g . • Garcia & Koelling, 1966). Conditioned aversion refers to the phenomenon where an organism associates a taste with subsequent illness, even though the gustatory stimulus may precede illness by several hours.Since, in a conditioned aversion situation, the rat is required to inhibit consumption of a previously ingested taste, one might expect developmental processes to influence the occurrence oftaste aversion. Young animals appear to have more difficulty than adults in passively avoiding an aversive event, where shock is the aversive stimulus (e.g., Riccio, Rohrbaugh, & Hodges, 1968;Riccio & Schulenberg, 1969). One purpose of the first experiment was to determine if young juvenile rats would avoid a taste whose consumption preceded illness.Novelty of the taste solution appears to be an important determinant influencing acquisition of a conditioned aversion (e.g., Garcia & Koelling, 1%7;Revusky & Bedarf, 1967). Animals develop aversions to novel tastes more rapidly than they do to familiar tastes (e.g., Fenwick, Mikulka, & Klein, 1975). Kalat and Rozin (1973) have suggested that when illness does not occur after consumption of a particular taste the rat learns that the taste is safe and can be ingested again. Thus, learned safety interferes with the development of aversions to previously experienced tastes. Young animals also appear to have more difficulty inhibiting previously appropriate responses than do adults. Egger (1974) found that 24-day-old rats extinguished an acquired escape response more slowly than either 50-or 100-day-old animals. Since, as a consequence offamiliarization, the subject learns that a particular taste is safe, young rats may exhibit more interference with taste aversion acquisition when previously experiencing that taste wi...
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