Figure 1. Saccadic tasks used.

(a) The 1DR task. After a fixation period of 1000 ms, a single eccentric stimulus appears at one of four locations and the subject is required to make a saccade to it. Stimulus location is chosen randomly in each trial. Fixation offset (go signal) and stimulus onset are simultaneous. In each block of trials, only one of the directions yields a large reward; the others yield either no reward (monkey G) or a small reward (monkey K). (b) The ADR task. Same sequence of events as in (a), except that saccades in all directions are equally rewarded. White arrows indicate saccades; they are not displayed.