Two mice were excluded from experiment 1 for nonperformance and 11 mice were eliminated due to equipment failure. Additionally, 2 mice died from unknown causes. In experiment 2, 13 mice were excluded for nonperformance. Not including the equipment problem, 16% of the total mice were excluded from the experiments for nonperformance. Six sessions were discarded from experiment 1, and 2 sessions were discarded from experiment 2 for noncompletion of 20 trials, amounting to 1.2 and 0.4% of the total sessions, respectively. There were no line differences in side preference during shaping in any experiment (ps > 0.39). For the critical last 20 trials data, the 95% confidence interval for mean delay preference (number of delayed choices divided by delayed plus immediate choices) was 45.7 to 51.6%, indicating a lack of preference for either lever. Therefore, adjusted amounts recorded on the immediate lever should accurately reflect indifference points.
