Fig 1. Task schematics.

(a) Experimental setup. Observers viewed MID stimuli in a virtual reality headset. The stimuli simulated dots moving toward/away from the observer through a cylindrical volume. Observers reported the perceived motion direction. (b) Motion-in-depth stimuli and temporal sequence. Binocular cues stimuli contained binocularly opposite horizontal motion cues. Monocular cues stimuli contained optic flow patterns shown to one eye only. Combined cues stimuli contained both cues at the same time. Full VR stimuli contained binocular and monocular cues, as well as motion parallax. Stimuli were presented for 250 ms. Auditory and visual feedback were provided to observers after they responded. The next trial started 750 ms after feedback. The number of dots, their sizes, and optic flow patterns shown here are intended to convey the MID cues, rather than to portray the exact stimuli. Movies illustrating the actual stimuli are provided in the Supporting Information.