Figure 1.

Methods. Panel a schematically depicts the sequence of events in the task for the monkeys. Once the animal fixates, the stimulus is presented on the screen for 2 s. After that two choice targets appear above and below the fixation marker. Only saccades made within 500 ms to the correct choice target were rewarded. Panel b, shows schematic views of the stimulus at different levels of inter-ocular correlation (100%, 50% and 0%). Upper row represents a front view, where red and yellow dots are shown to the left and right eye only, respectively. The bottom row shows a schematic view from above: the subject fixates, and the stimulus appears as a disc at the signal disparity (orange dots, 100% correlation), as a ‘cloud’ extending in depth (cyan dots, 0% correlation) or as a mixture of both (50% correlation). Panel c shows schematically how the psychophysical kernels are calculated. The distributions of noise dots (number of dots at each disparity) on each trial were sorted according to the subject’s choices. For both kinds of choices, the detection kernel is the average dot distribution minus the average number of dots per disparity across all trials (μ). N_near and N_far are the number of near choice-trials and far choice-trials. Because of the obligatory symmetry up to a scaling factor between the near and far choice detection kernels, they can be summarized by their difference (near choice detection kernel – far choice detection kernel).