Figure 1.

Experimental procedure. A, Top, Visually guided saccade task with an asymmetric reward schedule (1DR-VGS). After the monkey fixated on the FP for 1200 ms, the FP disappeared and a target cue appeared immediately on either the left or right, to which the monkey made a saccade to receive a liquid reward. The dotted circles indicate the direction of gaze. In a block of 20–28 trials (e.g., left-large block), one target position (e.g., left) was associated with a large reward, and the other position (e.g., right) was associated with a small reward. The position-reward contingency was then reversed (e.g., right-large block). Bottom, The trial sequence. Left- and right-large conditions were alternated between blocks. The sequence for the target position was pseudorandom, subject to the constraint that, within every four trials (2 trials for each of the 2 positions), the order was determined randomly. B, Changes in the mean normalized saccadic reaction times of all analyzed data before and after target-reward contingency reversal. Error bars indicate 1 SE. *p < 0.01 indicates that the reaction times of the particular trial were significantly different from those during the last five trials of the block (Mann–Whitney U test).