Extended Data Fig. 1: Task sequence and target shape primitives.

(a) Illustration of the complete task sequence. Note that for illustration purposes the background is shown as white, and the surrounding crowders are shown at reduced saturation relative to the centrally located targets. However, on the actual task display, the background was dark, and target luminance was reduced relative to the crowders (see Fig. 1c), in order to better obscure the targets when they are not being viewed directly. (b) The 7 shape primitives used to generate choice stimuli. To create a new stimulus set, four shapes are selected without replacement from the 7 primitives; then each is rotated randomly by 0, 90, 180, 270 degrees. The four rotated shapes are then combined with four colors selected randomly from equally-spaced points on a color wheel defined within the RGB gamut in the CIELUV color space. A sub-set of 12 targets is then selected, and assigned to reward values ranging from 1–5 drops (Fig. 1b).