Effortful touch with minimal movement.

Abstract

Perception of the extents of occluded rods was examined under conditions in which a rod was held as steadily as possible. A given rod was held horizontally, on one side of its center of mass, with one upward ((.') and one downward (D) force. Extent was perceived when D and U were distributed over the surfaces of 1 hand. 2 hands, and a hand and a knee and if only D or only U was provided anatomically, the other being provided by an environmental support. Increasing the distance between D and U decreased perceived extent when both contact points were anatomical and when only I was anatomical. The first moment of the mass distribution, a constant, affected perceived extent more than gravitational torque, a variable. Rods of different lengths but of the same first moment were not distinguished. Results are discussed in terms of functionally equivalent, haptic perceptual instruments and the detection of invariants.

Muscle-based perception: theory, research and implications for rehabilitation

“…Nonetheless, accuracy, reliability, and inertial dependencies are the same. Th e commonalities reported for any two-point stabilization of a rod 34 makes a similar point: Th e specifi c deformed tissue in not important, the deformation is. Certainly the rarity in the medical literature of complete haptic loss is telling.…”

“…For example, probing and wielding a rod with one hand, two hands, hand+knee, hand+axle or with a stick+axle result in the same perceptual outcome, namely, perceived length is a single-valued function of mass moments 33,34 . Th ere is no neural substrate in the stick, of course, hence, no sensations arising from local contact with the to-be-perceived rod.…”

Inertial eigenvalues, rod density, and rod diameter in length perception by dynamic touch

“…As he correctly pointed out, however, the tissue deformation in those experiments, unlike that registered from his reference segments, was brought about by the rod to be perceived. The conclusion of the Carello et al (1992) experiments was that the mass distribution, not the particular tissue contact, was important. That is why perceived length with hand and knee was equivalent to using one grasping hand, the top of one hand and the bottom ofanother, and even the edge ofone finger as the only tissue contact (with an environmental support providing the balancing force).…”

“…He recommended that this type of scaling be called "definite." In perceiving length by dynamic touch, participants exhibit definite scaling-although their perceptions are rarely the actual lengths, they are always in the range of actual lengths (Carello et al, 1992;Turvey & Carello, 1995; and see summary above). For the 82 objects of Fitzpatrick et al, Solomon and Turvey (1988, Experiments 1-2), and our Experiments 1-2 (i.e., those for which actual length varied), the range of perceived lengths was 23.0 to 94.9 em, with a mean of 47.9 em and a standard deviation of 17.0 em; the range of actual lengths was 21.2 to 91.4 em, with a mean of 59.8 and a standard deviation of 21.6 em.…”

Which Mechanical Invariants Are Associated With the Perception of Length and Heaviness of a Nonvisible Handheld Rod? Testing the Inertia Tensor Hypothesis.

“…The first moment is the mass (m) times the distance (d) between the point of rotation and the object's center of mass. Following Carello, Fitzpatrick, Domaniewicz, Chan, and Turvey (1992), we use the term static moment to indicate this invariant object property. 1 The second moment can be conceived as an object's resistance against angular acceleration.…”