Human (but not animal) motion can be recognized at first sight – After treatment for congenital blindness

Abstract

The long-standing nativist vs. empiricist debate asks a foundational question in epistemology – does our knowledge arise through experience or is it available innately? Studies that probe the sensitivity of newborns and patients recovering from congenital blindness are central in informing this dialogue.One of the most robust sensitivities our visual system possesses is to ‘biological motion’ – the movement patterns of humans and other vertebrates. Various biological motion perception skills (such as distinguishing between movement of human and non-human animals, or between upright and inverted human movement) become evident within the first months of life. The mechanisms of acquiring these capabilities, and specifically the contribution of visual experience to their development, are still under debate.We had the opportunity to directly examine the role of visual experience in biological motion perception, by testing what level of sensitivity is present immediately upon onset of sight following years of congenital visual deprivation. Two congenitally blind patients who underwent sight-restorative cataract-removal surgery late in life (at the ages of 7 and 20 years) were tested before and after sight restoration. The patients were shown displays of walking humans, pigeons, and cats, and asked to describe what they saw.Visual recognition of movement patterns emerged immediately upon eye-opening following surgery, when the patients spontaneously began to identify human, but not animal, biological motion. This recognition ability was evident contemporaneously for upright and inverted human displays.These findings suggest that visual recognition of human motion patterns may not critically depend on visual experience, as it was evident upon first exposure to un-obstructed sight in patients with very limited prior visual exposure, and furthermore, was not limited to the typical (upright) orientation of humans in real-life settings.