Further examination of ontogenetic limitations on conditioned taste aversion

This study was to resolve a discrepancy in the literature as to the capability of infant rats in acquiring conditioned taste aversion. Previous studies had indicated that during the 1st postnatal week, an aversion to saccharin could be conditioned when paired with lithium chloride (LiCl). Analogous conditioning with sucrose did not seem to occur until the end of the 2nd postnatal week, however, even though sucrose is discriminated from water and preferred before then. We observed that 5- and 9-day old pups express conditioned taste aversion to both saccharin and sucrose flavors that previously were paired with illness induced by LiCl. This learning occurred only when several hours separated cannulation and conditioning. A number of other factors that seemed likely to determine this early learning were found to have no effect. Thus it appears that rats can learn taste aversions very early in life, but only under certain circumstances. The results are discussed with reference to Vogt and Rudy's (1984) conclusions on the ontogeny of taste guided behaviors in the rat.