Do Positions Affect Perceptual Judgment during Reaching?

Abstract

[Purpose] We examined whether changes of position alter perceptions. [Subjects] The subjects were 23 healthy adults and one male adult with quadriplegia due to sequelae of head injury. [Methods] The experiment employed six positions for the healthy adults: side-lying, sitting with 45-degree reclining (reclining), dangling, long sitting, cross-legged sitting, and creeping position. Three positions were employed for the quadriplegia patient: side-lying, reclining, and sitting in an electric wheelchair (mimicking dangling). Using a functional-reach measuring instrument, to obtain the depth perception of distance between object and the subject’s arm length, the subjects were asked whether they thought the could reach the object or not. [Results] For healthy adults, the results showed no significant difference in the number of correct answers among all the positions. The quadriplegia patient examined in this study, however, showed a high number of correct answers while in the wheelchair sitting position, and low scores in the other two positions. [Conclusion] A subject?fs perceptual judgment of reaching is possible as long as he has experience of that particular position. By conducting exercises involving a variety of positions and environments, it may be possible to renew body image and reduce the recognition gap between body image and physical abilities.