Intermediate frames of reference in haptically perceived parallelity

Haptically perceived space was investigated in eight experimental conditions. The task of the subjects was to make an extensive field of bars parallel to another at a variety of fixed positions, either on a horizontal plane or on the midsagittal plane, and either with their right hand or with their left hand. Settings were correlated with the orientations of the hand when placed at the same locations in a natural way. The parallelity settings deviated systematically from veridical. The patterns of the deviations were the same for all subjects. These haptically perceived parallelity settings can be considered as decided in a subject-dependent frame of reference intermediate to allocentric and egocentric reference frames.