Delay discounting in college cigarette chippers.

Individuals who smoke cigarettes regularly but do not become dependent on them provide a unique opportunity for studying the factors that inhibit drug dependence. Previous research on this population, sometimes referred to as 'cigarette chippers', showed that they did not differ from regular smokers in terms of smoking topography (e.g. puff number and duration) and circulating nicotine levels, but that they did show more self-control according to answers on a questionnaire. We evaluated the generality of this finding using a behavioral choice procedure. The participants were undergraduate students (n=71), who were regular smokers, chippers, or nonsmokers. In the choice procedure, one option was a smaller but sooner amount of money, and the other option was a larger but delayed amount of money. Under these conditions, preference for the sooner smaller amount implies that the later larger monetary amounts were discounted. It is widely assumed that the rate of discounting provides an operational definition of impulsivity. In one version of the procedure, the money was hypothetical. In a second version, each choice had a chance of producing an actual monetary outcome. When there was an actual monetary outcome, regular smokers were more likely to choose the sooner but smaller monetary option than chippers and nonsmokers. For all participants, the rate of discounting decreased as the magnitude of the monetary outcomes increased, and for smokers and chippers the differences in discount rates in the two versions of the delayed outcome procedure were the same. These findings are consistent with the view that chippers are less impulsive than smokers. Quantitative aspects of these findings led to the hypothesis that discount rates decrease as a negative power function of the monetary value of the options. This result establishes an analogy between delay discounting experiments and psychophysical experiments. Results from two earlier studies support the analogy.