Changing the influence of the egocentric reference frame impacts deviations in haptic parallelity matching

Hanneke I Van Mier

doi:10.1007/s00221-019-05596-x

Abstract

The large systematic deviations in haptic parallelity matching are most likely due to the biasing influence of the hand-centered egocentric reference frame. Previous results showed that eliminating or reducing this bias resulted in smaller deviations, with significantly larger effects observed in female participants. The current study investigated the effect of reducing the egocentric bias in a pure haptic condition. Blind-folded male and female participants had to feel the orientation of a reference bar with their non-dominant hand and to parallel this orientation on a test bar with their dominant hand. In one condition, they were instructed to use their flat-stretched hand to feel and match the bars, while in the other condition (HPF), they were instructed to set the test bar while gripping the bar with the fingers and thumb. It was hypothesized that the latter would reduce the biasing influence of the hand-centered egocentric reference frame. Results showed that this was indeed the case. Deviations were significantly smaller for HPF; however, this effect was the same in both genders. The previously observed gender effect, showing a significantly larger improvement for women when reducing the influence of the egocentric reference frame, was not replicated.

Highlights

A spatial orientation task that might seem to be and veridically performed often results in large errors when the task has to be performed haptically without visual input
Because the observed deviations in this task have been found to be intermediate between what would be parallel in an allocentric and an egocentric reference frame, Kappers (2002, 2003) suggested that performance on the haptic parallelity task is most likely determined in an intermediate frame of reference in line with performance in reaching and grasping tasks (Flanders and Soechting 1995; Soechting and Flanders 1992)
The observed deviations seem to be the result of the use of an allocentric reference frame fixed in external space and an egocentric reference frame which is centered internally

Summary

Introduction

A spatial orientation task that might seem to be and veridically performed often results in large errors when the task has to be performed haptically without visual input. The orientation of a reference bar is felt with one hand, while the other hand has to rotate a test bar to match the orientation of the latter to the orientation of the former Performing this task without visual input results in a mismatch between what is perceived as being parallel and what is physically parallel. Because the observed deviations in this task have been found to be intermediate between what would be parallel in an allocentric and an egocentric reference frame, Kappers (2002, 2003) suggested that performance on the haptic parallelity task is most likely determined in an intermediate frame of reference in line with performance in reaching and grasping tasks (Flanders and Soechting 1995; Soechting and Flanders 1992). The influence of the egocentric reference frame has been found to be present in different settings of haptic matching tasks like in the horizontal plane

Objectives

Methods

Results

Conclusion