Mice were shaped according to the protocol outlined in Table 1. After the mice met criterion lever pressing in stage 4 (20 trials completed), side bias was assessed by averaging the last 3 days’ choices on each side. The large reinforcer was then assigned to their non preferred side, to counter any initial side bias. After shaping was completed, mice were assessed at the zero delay, which is not actually a delay but rather an assessment of magnitude discrimination. The criterion for continued inclusion of individual mice in this study was a mean adjusted amount of 1.5 seconds or greater (75% or more of the 2 seconds access on the delayed side) in 3 of 4 consecutive days. We used this inclusion criterion because any assessment of DD relies on magnitude discrimination. If individuals could not display a preference for the larger reward, then discounting of that assessment based upon time would be unreliable. Importantly, the adjusted amount derived at the zero delay was not the result of innate side bias, as the 75% adjusted amount requirement meant that the
