title: A blind human expert echolocator shows size constancy for objects perceived by echoes.
abstract: Some blind humans make clicking noises with their mouth and use the reflected echoes to perceive objects and surfaces. This technique can operate as a crude substitute for vision, allowing human echolocators to perceive silent, distal objects. Here, we tested if echolocation would, like vision, show size constancy. To investigate this, we asked a blind expert echolocator (EE) to echolocate objects of different physical sizes presented at different distances. The EE consistently identified the true physical size of the objects independent of distance. In contrast, blind and blindfolded sighted controls did not show size constancy, even when encouraged to use mouth clicks, claps, or other signals. These findings suggest that size constancy is not a purely visual phenomenon, but that it can operate via an auditory-based substitute for vision, such as human echolocation.
authors.affiliation: a The Brain and Mind Institute , The University of Western Ontario , London , Ontario , Canada.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Milne
authors.forename: Mimma
authors.initials: M
authors.lastname: Anello
authors.forename: Melvyn A
authors.initials: MA
authors.lastname: Goodale
authors.forename: Lore
authors.initials: L
authors.lastname: Thaler
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D000818:Animals; D001766:Blindness / Q000523:psychology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013017:Sound Localization; D013028:Space Perception
keywords: blindness; human echolocation; multisensory; size constancy; vision