While impulsive choices (e.g., eating the piece of cake we had decided to forgo, pushing the doze button on our alarm clocks when we had decided to get up early) are common in the daily lives of normal adults, higher levels of impulsiveness have been associated with more serious problems, such as substance abuse, eating disorders, and pathological gambling. The principal investigator and colleagues have developed two methodologies for assessing individual differences in impulsiveness based on choices between real rewards. These methods are based on a discounting model which states that the subjective value of future rewards is discounted as a function of the delay in time until the reward can be obtained. Impulsive choices are seen as arising from temporary reversals of preference between rewards that result from the nature of the discounting function. In such preference reversals, a smaller, earlier reward (SER) temporarily takes on a higher subjective value than a larger, later reward (LLR) that was initially preferred. In both methods, subjects are tested individually at a computer. Reward-valuation procedures, which will be employed in the majority of studies, present subjects with a series of delayed rewards for which subjects must """"""""bid"""""""" in a cleverly designed sealed, second-bid auction procedure, and give their present valuations. On the basis of these valuations, fitted functions can be used to assess the adequacy of different discounting models and to quantify individual differences in impulsiveness. The choice-titration procedure presents subjects with a series of choices between fixed pairs of SERs and LLRs, and manipulates the delays to those rewards on the basis of the subject's previous choices until a delay is found at which the subject is indifferent between the two rewards. This allows real choices to be used to uncover impulsive preference reversals. These two methods are complementary in that each overcomes limitations of the other. The broad long-term objectives of the proposed research are: (1) to refine the discounting model of impulsive behavior through a systematic investigation of the quantitative form of the discounting function and the variables that influence the cognitive calculus hypothesized to underlay impulsive choices; and (2) to apply the discounting model to the development of effective cognitive self-control strategies that can help to reduce impulsive behavior.
The specific aims of the proposed research are: (1) to test the hypothesis that linking future rewards will reduce impulsiveness; (2) to test the hypothesis that establishing behavioral patterns favoring choices of LLRs can reduce impulsiveness; (3) to test whether anticipated regret can reduce impulsiveness; (4) to determine whether impulsiveness differs according to the consumption rate of delayed rewards; and (5) to determine the relationship between the discounting construct of impulsiveness and other measures of impulsiveness.
