Factors affecting the size of the detour effect in the kinaesthetic perception of Euclidean distance

Abstract

Three experiments investigated the mechanisms by which we estimate Euclidean distances on the basis of kinaesthetic cues. In all experiments, blindfolded participants followed straight and curvilinear paths with a stylus. Then, with a straight response movement, they estimated the distance between the end-points of the previously explored path. Experiment 1 was designed to validate the hypothesis-made on the basis of results from a previous study-that errors in the kinaesthetic estimations of distances (detour effect) originate from the difficulty to decompose the displacement vector into relevant and irrelevant components, which would become more severe at points of inflection. Using elliptic paths (no inflections), we demonstrated that errors are indeed reduced considerably. The role of the orientation of the work plane was investigated in Experiment 2 in which the same paths used in our previous study were oriented in the frontal rather than the horizontal plane. The results indicate that the detour effect is independent of the orientation. Moreover, despite the asymmetry that gravity introduces between upward and downward movements, errors in the two directions are almost identical. Experiment 3 addressed two issues. First, we demonstrated that introducing a delay between the exploration of the path and the response did not alter significantly the pattern of errors. By contrast, we demonstrated that errors are severely reduced when the number of paths to be explored is reduced by half. The results of the three experiments are discussed within the context of current theories of sensori-motor coding.

The Effects of Curvature on Haptic Judgments of Extent in Sighted and Blind People

“…Moreover, the results are not limited to simultaneous exploration of the curves and tangible ruler (experiments 1 and 2), since they occurred with sequential, immediate-size estimates (eg experiments 3^7). The results are consistent with those reported by Faineteau et al (2005).…”

“…However, they failed to find any effect of frontal placement on judgments of extent. Their stimuli were oriented so that the distance between the endpoints of the stimuli was vertical (Faineteau et al 2005). In the present experiment, subjects in one group traced patterns while their right arms were supported by a board.…”

“…Note, however, that the subjects in experiment 7 judged the diameters of the curves, and not their heights. Height judgments may be more susceptible to the effects of a frontal placement (but see Faineteau et al 2005). However, it is still possible that perceptual distortion could derive from nonoptimal exploration, since subjects were limited to tracing with the index finger in most of the experiments reported here.…”

Attenuating the haptic horizontal—vertical curvature illusion

“…In the path completion problem, subjects feel a curve and then judge the distance between endpoints (see Faineteau et al, 2003Faineteau et al, , 2005Lederman et al, 1985). They are not permitted to actually feel the distance between endpoints, and the subjects in Experiment 1 were prevented from scanning between endpoints.…”

L’inférence haptique d’une localisation spatiale chez les adultes et les enfants : étude de l’effet du trajet et du délai dans une tâche de « complètement de triangle »

“…sur la précision des participants à reproduire haptiquement avec une main l'orientation d'une baguette située dans le plan horizontal préalablement exploré avec la même main. De la même manière, en kinesthésique, Faineteau, Gentaz et Viviani (2005) n'observent pas non plus un effet qualitatif du délai (3 sec. vs 12 sec.)…”