Differential errors of kinesthesis produced by previous limb positions.

Reports of kinesthetic after-effects indicate that the position sense of the limb is labile. It was hypothesized that varying the starting positions of a limb would be an important factor in determining the post-treatment accuracy of kinesthesia. An experiment is described in which the right arm was horizontally abducted to one of two treatment positions. The effect of exposure time at each of these positions was assessed for a set of testing positions by measuring subsequent accuracy of visual localization of the unseen finger tip. There was a marked unidirectional shift in registered position of the treated limb, which was to the left following postures on the right. The magnitude of this change in kinesthesis was significantly greater when the treatment position was farthest from the test position. Exposure time affected only the nearer treatment position.