Biomedical subjects

D Barac-Cikoja

Publications and source records attributed to D Barac-Cikoja.

4 recordsLinked to original sources

PubMed1999

Anisotropy in the extended haptic perception of longitudinal distances.

Using horizontal rotational motions of a hand-held rod, participants in four experiments probed the aperture between two blocks separated in depth. The farther block could be either on the outer or on the inner side of the hand-rod system, defining apertures of opposite sense. The participants reported the perceived size of the in-depth intervals by adjusting, with the nonprobing hand, the lateral separation between two blocks or the egocentric distances of two blocks. Over variations in hand and geometric arrangement of stimulus and report blocks, perceived aperture size depended on the aperture's sense: Apertures with the farther edge on the outer side of the hand-rod were reported as being larger than their mirror image counterparts. The effect was not observed in judgments of a single edge distance (Experiment 5); it was configuration dependent. The sense effect would not be expected from the physical quantity accommodating perceived frontal apertures. Possible expansions of the physical model are discussed.

Adult↗

PubMed1995

Does perceived size depend on perceived distance? An argument from extended haptic perception.

Two experiments were directed at the comparison between two perspectives on the perception of size achieved by probing the gap between two occluded distal surfaces by means of a hand-held rod. One perspective was the classical size-distance invariance hypothesis developed for the problem of visual size perception with a central role for perceived distance; the other was the hypothesis that the extended haptic perception of gap size is specific to a physical invariant lambda of the dynamics of probing. Experiment 1 examined the relation between hepatically perceived gap size and haptically perceived gap distance. No causal connection between the two was found, and all the variance in perceived size was accounted for by lambda. Experiment 2 manipulated the rotational inertia of the probe. Its effect was different for the two perceptions of size and distance, underscoring their independence. The indifference of perceived size to perceived distance was discussed in reference to identifying invariants for both the haptic and the visual perception of size at a distance.

Adult↗

PubMed1993

Haptically perceiving size at a distance.

Six experiments are reported on perceiving the sizes of gaps by probing with a hand-held rod. A collective parameter, lambda, is invariant over the time-varying dynamics of probing: lambda = sin(alpha/2)[1-(2a/b) + (a/p)] = sin(alpha/2) delta, where alpha is the angular excursion of the rod-plus-limb segment and a, b, and p are the distances, respectively, of the center of mass, point of contact, and the center of percussion from the axis of rotation. If perceived size is specific to lambda, then it should (a) be a single-valued function of lambda regardless of the muscles executing, and deformed by, the probing; (b) equal, underestimate, and overestimate actual size according to 2b/delta = 1, 2b/delta < 1, and 2b/delta > 1, respectively; and (c) change with actual size at a rate equal to (1/2b-a/b2 + a/2bp), the partial derivative of lambda with respect to size. The experimentally confirmed predictions are discussed in relation to hypotheses about the specificity of perception to information, and the tensorial nature of dynamic touch.

Adult↗

PubMed1991

Perceiving aperture size by striking.

This study examined the ability to perceive surface separation on the basis of mechanical stimulation resulting from striking the surfaces' interiors with a hand-held rod. The variables manipulated were aperture size, angular displacement theta, distance b of the point of contact with the surfaces from the axis of rotation, hand-rod mass m, location of the hand-rod's center of mass a, and moment of inertia Io of the hand-rod. Given a particular rod and an aperture at a given distance, lambda = sin(theta/2)[1 - (2a/b) + (ma2/Io)] was invariant over explorations. Perception of aperture size was specific to lambda; it predicted successfully the interdependent effects of theta, b, and the mechanical properties of the implement. The results of 7 experiments were discussed in terms of the specificity of perception to information and the general ability to perceive distant things by means of body appendages.

Adult↗