The objective of the project is to study the cognitive and behavioral effects of combined doses of tobacco and alcohol compared with the effects of each substance administered separately. This research is expected to help clarify whether or not the two substances together have similar effects or offsetting effects on subjective and cognitive processes. Our aim is to determine dose-response functions for several cognitive and learning processes for tobacco alone, alcohol alone and the two substances combined. Goals for the current year have been to develop tasks which are sensitive to tobacco effects and to begin to establish a dose-response data base for tobacco alone. Such a data base is necessary before beginning the more complex interaction studies because there is virtually no consistency in the published data on effects of tobacco on human cognition and learning. To accomplish this goal we have initiated two lines of research: (1) the effects of tobacco on memory storage and retrieval of verbal information, (2) the effects of tobacco on rate of habituation of physiological responses to repetitive stimuli. An initial study has been completed in which we examined the effects of cigarette smoking on two phases of human verbal learning: initial acquisition and recall of peviously stored information. Subjects were classified into low nicotine (.50 to .80 mg/cigarette), medium nicotine (1.00-1.06mg) and high nicotine (1.17 to 1.30 mg) groups. Each subject participated in 3 sessions: No Smoke and Smoke-Before-Learning and Smoke-After-Learning sessions. The Smoke-Before-Learning condition resulted in better recall than the No Smoke condition for the low nicotine group but not for the other two groups. For the Smoke-After-Learning condition the low nicotine group again produced higher recall following smoking than no smoking.