Behavioral performance of contingent and noncontingent subjects on the five-choice serial reaction time task over 2 consecutive days of testing. During the experiment, animals were head-tethered to a counterbalanced spring support to allow the simultaneous application of in vivo microdialysis during task performance. The stimulus duration and intertrial interval were 50 and 500 csec, respectively. Each bar represents successive 5 min bins over 1 hr (±SEM; n = 10) for contingent (white bars) and noncontingent (striped bars) subjects. It can been seen that animals in the contingent group maintained a stable level of performance over both days, whereas noncontingent subjects extinguished responding for target stimuli and made more anticipatory responses and magazine entries.