Finally, Ingrid Johanson and Martin Teicher (1980) researched classical conditioning in 3-day old rat pups. 50 pups that were separated from their mothers for 24 hours before the experiment (i.e. deprived pups) were divided into five groups of ten. Pups in the conditioning group went through one trial per minute for 10 minutes. Before conditioning, milk infused into the pup’s mouths was the UCS, their mouths reflexively swallowing in response to the milk was the UR, and the odor of cedar (an aversion stimulus) was the NS. During conditioning, the cedar odor was presented for 20 seconds, and during the last 5 seconds of this 20 second period, milk was infused into the pups’ mouths. Thus, the cedar odor (now the CS) was associated with the milk
