he rats promptly learned to associate a taste CS with a UCS of nausea but not with the foot-shock, where the audiovisual CS was conditioned to the foot-shock but not to nausea (Walker 1995).Taste aversion has violated three principles of classical conditioning, the first is that equal associability of stimuli: any CS can be paired with any UCS. This has proven to be untrue because if it were, the rats that became sick would have avoided both the salty water CS and the audiovisual CS. The second principle violated is temporal contiguity: CS and UCS have to be presented close together in time. Again untrue in this case because of such a long delay between drinking the salty water and becoming sick. The third and final principle is that learning is gradual, but in this case only one trial was enough.The studies done by Garcia and Koelling have had much support from many other experiments done in similar or the same situations. A study of ingestional aversion (Gregg, Melanie, Kittrell, Domjan & Amsel, 1978), where 12 and 15 day-old rats were conditioned by infusing a .5% solution of saccharin into the oral cavity. This was then followed by an oral infusion by the injection of lithium chloride. At both ages, subjects that had saccharin exposure was followed by a lithium injection within 2 to 3 minutes drank less when the saccharin solution was again presented by oral infusion 12 hours later. Ingestional aversions were also learned by 12-day-olds when an interval as long as 30 minutes was introduced between saccharin exposure and lithium toxicosis, however there was no sign of aversion to the saccharin solution when the toxicosis was delayed by 120 minutes. In contrast, the 15-day-olds were able to learn aversion with both the 30 minute and 120 minute delay intervals. Although the absence of 120 minute long-delay learning in 12 day olds, further experiments show that ingestional aversion conditioned at 12 days of age were retained for 2 weeks...
