Figure 5.

The contrast detection task. The monkeys performed a contrast detection task in the presence or absence of two collinear flankers. We presented collinear flankers or no flankers during the initial fixation interval. After 500 ms of fixation, a Gabor target appeared at the receptive location (RF) for 200 ms or no Gabor stimulus was presented. After an additional 400 ms, the monkey reported his choice by either making an eye movement toward a marker (black circle) at the RF if he had seen the target or by maintaining fixation if not. Six (or seven) different contrast levels (3–20%) of the central stimulus were tested. Trials with and without the flankers were presented in separate blocks.