Lateral congruence of eye and hand improves physical matching during estimation of line length
Date
1999
Authors
Kondzielewski, Thomas
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Abstract
This study considers judgements of the length of parallel lines which recede in depth from normal viewers. The intention is to clarify neuropsychological models of variation in spatial representation, in terms of sensorimotor action, attention, and visual perception. Milner, Harvey, Roberts, & Forster (1993) suggest that subjective space could be progressively compressed towards the left, especially for those with right hemisphere brain damage. Finding of Heilman, Chatterjee & Doty (1995) could be interpreted as endorsing this effect for normals who binocularly perceive straight lines in left spaces as looking smaller than lines in right space during judgements of receding line length. The current study replicates and extends this finding, with right side lines being accurately recreated in left space, but left side lines recreated shorter (underplaced) in right space. There is no combined effect of monocular sighting eye dominance and visual angle of retinal image upon binocular line length recreations. Comparison between binocular and monocular findings only support a cyclopean binocular viewpoint for near lines. For far lines, congruent (ipsilateral) eye and hand together recreate accurate line lengths while incongruent (contralateral) eye and hand is influenced by retinal image (indicating misperception of line orientation and/or depth). This evokes Berner and Berner's (1953) crossed (eye and hand) dominance syndrome. The flexibility of the binocular controlling eye may be complemented by an unexpectedly variable monocular sighting eye performance independent of the avowed monocular sighting eye dominance or hemispatial origin of the ey/hand combination. Instead, more accurate perception of line orientation in farther space occurs when both required body systems are those yoked to same lateral hemispace. This supports previous finding of laterla congruence (Burden et al., 1985) between multiple body-based maps and lateral hemisphere.