Immediate susceptibility to visual illusions after sight onset.
The dominant accounts of many visual illusions are based on experience-driven development of sensitivity to certain visual cues. According to such accounts, learned associations between observed two-dimensional cues (say, converging lines) and the real three-dimensional structures they represent (a surface receding in depth) render us susceptible to misperceiving some images that are cleverly contrived to contain those two-dimensional cues. While this explanation appears reasonable, it lacks direct experimental validation. To contrast it with an account that dispenses with the need for visual experience, it is necessary to determine whether susceptibility to the illusion is present immediately after birth; however, eliciting reliable responses from newborns is fraught with operational difficulties, and studies with older infants are incapable of resolving this issue. Our work with children who gain sight after extended early-onset blindness, as part of Project Prakash, provides a potential way forward. We report here that the newly sighted children, ranging in age from 8 through 16 years, exhibit susceptibility to two well-known geometrical visual illusions, Ponzo [1] and Müller-Lyer [2], immediately after the onset of sight. This finding has implications not only for the likely explanations of these illusions, but more generally, for the nature-nurture argument as it relates to some key aspects of visual processing.
Department of Electrical Engineering, Indian Institute of Technology Delhi, New Delhi 110016, India; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. Electronic address: gandhitk@gmail.com.
Tapan
T
Gandhi
Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Amy
A
Kalia
Department of Pediatric Ophthalmology, Shroff Charity Eye Hospital, New Delhi, India.
Suma
S
Ganesh
Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Pawan
P
Sinha
D000293:Adolescent; D001766:Blindness / Q000601:surgery; D016022:Case-Control Studies; D002387:Cataract Extraction; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D009903:Optical Illusions; D014785:Vision, Ocular