IQ and nonplanning impulsivity are independently associated with delay discounting in middle-aged adults

Impulsivity is a complex and multidimensional construct measured using both self-report measures and objective behavioral tasks. However, most studies using behavioral tasks have utilized relatively small homogeneous populations. In this project we examined both self-reported impulsivity, using the Barratt Impulsiveness Scale (BIS), and delay discounting, a behavioral measure of preference for immediate over delayed rewards, in a large sample of adults (N=606). Performance on the self-report and behavioral measures was examined in relation to demographic characteristics including age, sex, race, IQ, years of school and family income. Using hierarchical multiple regression we found that preference for immediate rewards was related to the Nonplanning impulsiveness subscale of the BIS and, after controlling for other variables, also related to intelligence. The finding that delay discounting, or preference for immediate rewards, is related to intelligence even after taking into account other variables, including socioeconomic indicators, suggests that there may be previously unrecognized links between this form of impulsivity and intelligence. This also suggests that intelligence should be taken into account in studies designed to measure impulsive behaviors. (c) 2006 Published by Elsevier Ltd.