Figure 1.

Stimuli (left) and trial progression (right) for experiment 1. Left. Pre-trained known paired associates used in experiment 1. Right. Example of an exclusion trial from experiment 1. Monkeys initiated trials by touching the green start box. A sample image appeared in the center of the screen. After this image was touched, four comparison images appeared randomly in the four corners of the screen. On exclusion trials, selection of the novel comparison image (lower left corner in the figure) from among the three known images resulted in a reward, whereas choice of one of the incorrect known comparison images resulted in a time-out period and no reward.