Binocular disparity augments the capacity of vision independently of subjective experience of depth

Frontal eyes are one of the defining features of primates. The horizontal separation of the eyes enables accurate calculation of depth which greatly improves eye-hand coordination - this is considered the key factor driving the evolution of frontal eyes. Although binocular disparity also results in a tangible subjective experience of three-dimensional world, it remains unknown whether disparity also augments objective perceptual performance. By utilizing realistic immersive virtual reality stimuli, we show that binocular disparity enhances the capacity of visual perception in humans: when visual disparity was present, participants were able to individuate more objects from the background more accurately, and do this faster. Interestingly, this effect also emerged without a concurrent enhancement in subjectively experienced depth, suggesting that the perceptual advantage provided by binocular disparity can arise independently of the subjective experience of space. The perceptual advantage provided by binocular disparity may have enabled more efficient visual behaviour during evolution.