Nicotine self-administration in animals: A reevaluation

Nicotine self-administration in animals is often viewed as compelling evidence that nicotine is reinforcing to animals and as corroborating the widely accepted thesis that nicotine is a major cause of smoking. This review examines the studies of nicotine self-administration in animals in the past two decades, focusing on threats to the internal and external validity of these studies and on the extent to which they support the thesis that nicotine is reinforcing in animals. The review shows that nicotine self-administration studies are fraught with severe methodological problems. These include omission of essential controls for general activation and other systemic effects of nicotine, insufficient consideration of secondary reinforcement processes, using food-deprived or confined animals and exclusion of subjects that do not conform to the investigators' preferred behavior. As a result of these systematic flaws, the role of nicotine as a reinforcer in this paradigm has not been established.