of extinction differed for infants and adults. Our subsequent experiments have confirmed these some conclusions in identical tests following careful equation of extinction levels for rats of the two ages ( Spear & Kucharski, 1984).
Our basic finding was that potentiation of conditioned aversion to a flavor was greater for preweanling and adult animals. Analysis focused on the enhanced conditioning to sucrose that resulted from presenting it in solution with coffee flavor. For preweanling animals this potentiation was sufficiently strong to override their otherwise ubiquitous deficiency, relative to adults, in conditioning with a delay between the CS and US. Potentiation was not seen for either infants or adults if the two flavors were presented successively, one immediately following the other, and especially for the infants, extinction of the association between coffee and LiCl reduced (in fact, eliminated) the potentiated conditioning of the sucrose solution.
To assess the generality of the basic results, we first replicated the original observations with a slight modification in certain control conditions. We determined also that the some ontogenstic difference occurred with