1, in comparing the slope during the first month of delay and the slope from 11 to 12 months of delay, it is clear that although the absolute delay durations are identical, the devaluation applied in the short run is considerably steeper. Abbreviated choice tasks also have been developed to more efficiently characterize discounting (e.g., Kirby, Petry, & Bickel, 1999; Madden, Petry, & Johnson, 2009) and are based on the hyperbolic model but can be also be analyzed using impulsive choice ratios (e.g., Murphy & MacKillop, 2012). Indeed, even very small numbers of items or a single item can be used to infer discounting rates (Anokhin, Golosheykin, Grant, & Heath, 2011; Bradford, 2010; Reimers, Maylor, Stewart, & Chater, 2009; Wulfert, Block, Santa Ana, Rodriguez, & Colsman, 2002). At this point, while there is no single methodology that is uniformly accepted as the most valid index of discounting, it appears that measures with greater precision are more sensitive (MacKillop et al., 2011).
