Fig. 1: Saccade foraging task.

a Two example trials of the saccade foraging task. The 4 × 4 array was composed of targets of three colors. Each target color was associated with a particular value determined by its water reward magnitude divided by the fixation time required to harvest this reward. When monkeys fixated a target for the pre-specified time, the color would turn into an equiluminant gray and corresponding reward was delivered, cueing the move to the subsequent target. In this example block, the rank of target values descended from green to blue to red. For illustration purposes, purple is used to represent red color in task paradigm. In successive trials, the association between color and value remained constant but the location of the colored targets within the array was randomized. The array size and orientation were tailored such that when the monkey was fixating a target (white cross), an adjacent target was positioned in the center of the pre-mapped response field (RF) of the isolated SC neuron (white dashed circle). The white arrows illustrate how the fovea and RF move in tandem as monkeys foraged targets in the array (More detail in Supplementary Movie 1). In a small number of experiments, larger response field eccentricities necessitated smaller 3 × 4 or 3 × 3 target arrays to fit on the visual display. b Examples of different menus. As monkeys tended to harvest targets in descending order of their value, the menu of items went from 3-values remaining (top), to 2-values remaining (middle), and finally 1-value remaining (bottom).