The present study also adds to the literature on DD and SES. We found that adolescents from lower-income families were more likely to choose immediate but smaller rewards, which is consistent with a previous study involving choices between hypothetical amounts of money conducted on a population of older adults (Green et al. 1996). Taken together, these findings suggest that SES is inversely associated with DD across age groups (adolescents and elderly) and reward types (real and hypothetical rewards). One possible explanation for this finding is that there is a causal relationship between propensity to discount delayed rewards and SES, and that this relationship is genetically mediated. There is evidence for genetic influences on SES indicators such as occupational status and educational attainment (Heath et al. 1985; Tambs et al. 1989), and these genetic influences could be mediated by individual differences in DD. For example, individuals with a genetically influenced “impulsive” decision making style may have a propensity to choose smaller but immediate gratification (such as going to parties or watching television) at the cost of larger but delayed rewards (such
