Fig. 1.

Sequence of events in a typical trial in the serial action task (A), variable reward task (B), and long delay task (C). Arrows indicate saccades, and dotted circles indicate the direction of gaze. The time indicated at the bottom of each image is the minimal possible duration of fixation during the corresponding stage of the trial. A: in the serial action task, the identity of a picture served as a sequence cue (e.g., the picture of a butterfly instructed the monkey to make an upward saccade during the first trial phase, a saccade down and to the right during the second phase, and a saccade down and to the left during the third phase). Six different pictures signaled the six different sequences in which the three targets could be selected. B: in the variable reward task, the bottom image illustrates the visual cues used to signal the reward a monkey would receive after saccade toward the cue; cues in one pair signaled a small reward (one drop of juice) and cues in the other pair signaled a large reward (three drops of juice). C: in the long delay task, the interval between onset of the target and permission to execute a saccade had a duration (4.7 s) that was approximately equal to the duration of an entire trial in the serial action task.