Figure 1. Sequential Inference Task.
(A) Trial flow. The monkey stares at a central fixation point at the beginning of a trial, and two choice targets appear, followed by a sequence of shapes, which are shown in succession every 250 ms. Each shape supplies evidence bearing on whether a reward is associated with one or the other choice target. The sequence continues until the monkey initiates an eye movement to a choice target. The reaction time is the interval from the onset of the first shape to initiation of the saccadic choice.
(B) The shapes shown on a trial are independent, random draws from either of the two discrete sampling distributions (indicated by color). On each trial, the designation of the correct (rewarded) choice is randomized to Target A or B, and the shapes are sampled accordingly. The ratio of sampling probabilities associated with each shape implies that half of the shapes support one or the other choice. Target A refers to the left choice target for monkey E and the red choice target for monkey J.