Conditioned alcohol-like and alcohol-opposite responses in humans.

Conditioned heart rate and skin temperature responses of 12 social drinkers were observed following repeated exposure to alcohol. Each subject received alcohol for four sessions in one room and a non-alcoholic drink for four sessions in a room of quite different appearance. Alcoholic and non-alcoholic drinks were distinctive and the alcoholic content could not be determined on the basis of taste. In the final three testing sessions, placebos were presented in order to test the influence of room and drink cues separately and in combination. A conditioned heart rate response opposite in direction to the alcohol effect was elicited by room and drink cues in combination and by the room cue in isolation. These results were in accordance with the predictions of the conditioning model of tolerance. A conditioned heart rate response in the same direction as the drug effect was elicited by the drink cue presented in isolation. Similar, but non-significant changes were also obtained with skin temperature. In addition, conditioned responses occurred independently of any expectancy. The results demonstrated that the direction of conditioned drug responses may depend on the type of stimulus presented.