Fig 1. Behavioral tasks.

(A) Single Fractal Task. Monkeys searched for a single fractal target without any surrounding environment. (B) Search Task. Monkeys were pre-cued with a visual environment, then searched for a single fractal target embedded in that environment. Yellow arrow indicates the required location of gaze. (C) One set of targets gave juice reward, while another set gave no reward. (D) Each environment consisted of 12 unique fractals at specific locations on screen. The single target fractal on each trial appeared randomly at one of four locations. (E) There were five unique environments, with different probabilities of their trial’s target being a reward target (as opposed to a no reward target). (F) Monkey M showed a stable reward-related bias during the last 20 sessions of both tasks, with shorter search durations on reward trials than no reward trials. This reward-related bias was stronger in the Search Task than the Single Fractal Task.