Methods and behavior. A, The animals were presented with 40 s blocks of an Eye (green target), Arm (blue target), or Fix (gray distractor) task. Operant behavior tasks were presented as single-cue (left and middle left) or multiple-cue (middle and right middle) tasks. B, After a fixation period, target and go cues appear on the screen. The dimming of one of the possible gray go cues served as the go signal for the multiple-cue tasks, while the dimming of the red fixation point served as the go cue for the single-cue tasks. Animals had to make an eye movement toward the green target or move the hand ipsilateral to the blue target. Fixation had to be maintained in the absence of a blue or green target. C, Types of events. Solid blue arrows indicate correct (c) switches between operant behavior; dashed blue arrows indicate correct stay trials (following another correctly executed trial) randomly selected from the same block as the switch trial; red arrows indicate incorrect (x) switch trials; dashed red arrows indicate incorrect stay trials (x) randomly selected from the same block as the incorrect switch trial. D, Total number of switch trials in all runs. Switch trials are divided per type of switch (e.g. EyeFix: switch from Eye to Fix). The bar color indicates the direction of the operant behavior in the switch trial (dark gray, left; light gray, right). White indicates a neutral condition, in which the animal was presented with only the central fixation point (no direction indication; only for monkey U). Smaller dotted bars with dashed outlines show the number of incorrect switch trials. E, Total number of trials in control experiments. Left, Monkey U, switching between Arm and Fix. Right, Monkey K, switching between Eye and Fix.