incorporate temporal discounting as a distinct component. Furthermore, correlations between DD measures and self-reported impulsivity have been fairly modest (Beck and Triplett 2009; Richards et al. 1999) or non-significant (Reynolds et al. 2006), suggesting that DD may represent a construct that is distinct from other aspects of a broader “impulsivity” construct. Studies have demonstrated good test–retest reliability of DD measures (Ohmura et al. 2006; Beck and Triplett 2009), but the origins of these stable individual differences remain unclear. Recently, studies using animal models have provided some evidence for genetic influences on DD: significant strain differences in DD were found in rats (Wilhelm and Mitchell 2009) and increased DD has been reported in mice selectively bred for alcohol preference (Mitchell et al. 2006; Oberlin and Grahame 2009). However, we are not aware of published studies estimating heritability of DD in humans.
