ABSTRACT
The perceived orientation of hand-held objects has been studied by asking subjects to wield an occluded L-shaped rod and adjust a visible pointer to coincide with the felt direction of the branch of the L relative to the hand. This chapter reports two additional experiments that demonstrate that the orientation of the crosspiece of a T-shaped object, held at the base of the T, cannot be apprehended by dynamic touch. This is because the orientation of eigenvectors of minimal (e3) resistance to rotational acceleration does not change as the crosspiece is rotated about a fixed stem. The crosspiece is, in effect, rotating about e3, leaving e3 unchanged. Placing differently, the orientation of the T-shaped object is not specified by the inertia tensor, thus it may be expected that the orientation of a T-shaped object may not be apprehended by dynamic touch. Perception by dynamic touch appears to be governed by the shape and orientation of the ellipsoid of inertia.
