title: Descartes's blind man revisited: bimanual triangulation of distance using static hand-held rods.
abstract: Analogous to binocular convergence, we tested Descartes's proposal that a blind person could triangulate distances using crossed hand-held rods by sensing hand separation and wrist angles. In Experiment 1, 22 participants judged distances to loci at 4 distances, 18-36 in. (45.7-91.4 cm), at 5 eccentricities, 0-12 in. (0-30.5 cm) left and right of center. Participants reliably differentiated and scaled distances. The median individual multiple correlation (actual distances and eccentricities vs. judged distances; nonlinear with eccentricity) was .91 (range, .75 to .95; group R = .98). In Experiment 2, 2 experienced observers judged 7 distances, 30-66 in. (76.2-167.6 cm) at 7 eccentricities, 0-18 in. (0-45.7 cm) left and right. Results replicated those of Experiment 1, with nonlinear multiple Rs of .97 and .99 for the 2 participants. Bimanual triangulation supported reliable distance judgments, comparable to binocular distance perception. No evidence of perceptual learning was found.
authors.affiliation: Department of Psychology, University of North Carolina at Pembroke, P.O. Box 1510, Pembroke, NC 28372-1510, USA. patrick.cabe@uncp.edu
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Cabe
authors.forename: Cheryl D
authors.initials: CD
authors.lastname: Wright
authors.forename: Mark A
authors.initials: MA
authors.lastname: Wright
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D004215:Distance Perception; D006801:Humans; D007600:Judgment; D007699:Kinesthesis; D008960:Models, Psychological; D011214:Practice, Psychological; D012044:Regression Analysis