Figure 1.

Target selection task. Each square shows the spatial arrangement of the task. Red filled circles are targets and green filled circles are distractors. The required saccade is indicated schematically by black arrows and actual saccade trajectories are shown as black dots. The black circle in the center of each square is the fixation spot. In the task, the array appeared and the fixation spot disappeared simultaneously. a, The monkeys' task was to make a saccade to the spot presented alone in the visual field or to the differently colored spot (either green among red or red among green spots) as shown in b. c, Example of the single target case. These trials were interleaved randomly with four stimulus trials. The monkey performed this condition with 100% accuracy. d, An array of three, differently colored distractors (green filled circles) appeared simultaneously with a red target. In this example the monkey performed the task with a >75% accuracy because some saccades (black dotted lines) were made to the green spots (errors). e, An example of the same monkey's performance on the same experimental day for trials in which target choices were made with <75% accuracy. Many saccades were made to the distractors (green circles). f, A subset of the trials shown in e when the monkey made all errors. Note that the target and distractor positions are normalized to 45, 135, 225, and 315 positions.