Reducing the motor response in haptic parallel matching eliminates the typically observed gender difference

Abstract

When making two bars haptically parallel to each other, large deviations have been observed, most likely caused by the bias of a hand-centered egocentric reference frame. A consistent finding is that women show significantly larger deviations than men when performing this task. It has been suggested that this difference might be due to the fact that women are more egocentrically oriented than men or are less efficient in overcoming the egocentric bias of the hand. If this is indeed the case, reducing the bias of the egocentric reference frame should eliminate the above-mentioned gender difference. This was investigated in the current study. Sixty participants (30 men, 30 women) were instructed to haptically match (task HP) the orientation of a test bar with the dominant hand to the orientation of a reference bar that was perceived with the non-dominant hand. In a haptic visual task (task HV), in which only the reference bar and exploring hand were out of view, no motor response was required, but participants had to “match” the perceived orientation by verbally naming the parallel orientation that was read out on a test protractor. Both females and males performed better in the HV task than in the HP task. Significant gender effects were only found in the haptic parallelity task (HP), corroborating the idea that women perform at the same level as men when the egocentric bias of the hand is reduced.

Minute hands of clocks indicating the same time are not perceived as haptically parallel

“…Deviations in the parallel setting experiment were also consistent with many earlier studies e.g. 1 – 6 and as always, they were quite substantial (on average the right bar needs a clockwise rotation of 57° with respect to the left bar in order to be felt as parallel). The deviations in the clock time estimate and clock time setting experiments were significantly smaller than in the parallel setting experiment (two-handed deviations were −18° and 19°, respectively).…”

“…The errors made in this condition were still systematic, but reduced to about half the size of the parallel settings. Such a reduction was also found if only a protractor without a test bar was shown and participants had to respond with a coded orientation 6 . A further reduction of the size of the deviations was found when participants with vision of their test hand had to draw a line instead of setting a test bar 5 .…”

“…Many studies have already shown that human perception of spatial relations is not veridical e.g. 1 – 6 . In these studies, the task of the blindfolded participants is to change the orientation of a test bar in such a way that the bar feels parallel to a similar bar at a different location.…”

Response Modality vs. Target Modality: Sensory Transformations and Comparisons in Cross-modal Slant Matching Tasks

“…The results in the unimodal conditions (HH and VV) were consistent with previous studies of haptic parallelity 34 , 41 and visual slant perception 26 , 28 in which the haptic bias reflected the strong influence of an egocentric RF, and the visual bias showed systematic overestimation of steepness when the test location was above the reference location. Similar to the findings of Volcic, Kappers and Koenderink 31 , the deviation of HH condition increased with the distance between the two surfaces.…”

“…A RF intermediate to an allocentric frame and a body-centred egocentric frame has been proposed for haptic parallelity tasks 27 , 29 . However, most of these studies focused on one or two kinds of modality conditions, such as haptic-only 4 , visuo-only 28 , visuo-haptic 26 , 32 , 33 or haptic-visual 34 tasks, and did not investigate the transformations and comparison among RFs.…”