typically not been found to be substantially related to discounting (e.g., MacKillop & Tidey, 2011), but this is not always the case and the role of income should be considered nonetheless. In contrast, aspects of cognitive function have been consistently associated with discounting (Bickel, Yi, Landes, Hill, & Baxter, 2011; Hinson, Jameson, & Whitney, 2003; Jaroni, Wright, Lerman, & Epstein, 2004; Shamosh et al., 2008). This is not surprising, as the process of discounting decision-making involves simultaneously juxtaposing the appeal of one immediately available reward in the present with another of larger magnitude in the future, requiring abstraction, working memory, inhibition, and other cognitive faculties. Moreover, genetic factors have also been implicated in cognitive functioning (e.g., Dickinson & Elvevag, 2009), making these processes high-risk confounds if not simultaneously considered. Thus, high-quality assessment of the discounting phenotype would optimally also characterize these related factors to incorporate their role and to avoid misattribution of genetic associations.
