Experimental control was performed using the open-source REC-GUI system (RRID:SCR_019008) (Kim et al., 2019 (link)). Stimuli were presented on a 24” Acer GN246HL LED monitor (1920 × 1080 pixels, 120 Hz) at a viewing distance of 57 cm. Stereoscopic presentation was achieved by temporally interlacing left- and right-eye images using an NVIDIA 3D Vision 2 Wireless Glasses Kit. We modified the glasses for a macaque interocular distance. The crosstalk (averaged across eyes) when the maximum or minimum stimulus luminance was presented to the ‘closed’ eye and the background was presented to the ‘open’ eye was low: 1.85% and 0.88%, respectively (Woods, 2012 (link)). The stimuli were created in MATLAB R2015a using Psychtoolbox 3 (Kleiner et al., 2007 (link)), and rendered with anti-aliasing using an NVIDIA Quadro K4000 graphics card on a Windows 7 workstation.