Contact forces in roughness discrimination

Roberta D Roberts,Harriet A Allen,Massimiliano Di Luca,Alan M Wing,Aldrin R Loomes

doi:10.1038/s41598-020-61943-x

Roberta D Roberts, Harriet A Allen + Show 3 more

Open Access

https://doi.org/10.1038/s41598-020-61943-x

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Abstract

Roughness perception through fingertip contact with a textured surface can involve spatial and temporal cues from skin indentation and vibration respectively. Both types of cue may be affected by contact forces when feeling a surface and we ask whether, on a given trial, discrimination performance relates to contact forces. We examine roughness discrimination performance in a standard psychophysical method (2-interval forced choice, in which the participant identifies which of two spatial textures formed by parallel grooves feels rougher) while continuously measuring the normal and tangential forces applied by the index finger. Fourteen participants discriminated spatial gratings in fine (spatial period of 320–580 micron) and coarse (1520–1920 micron) ranges using static pressing or sliding contact of the index finger. Normal contact force (mean and variability) during pressing or sliding had relatively little impact on accuracy of roughness judgments except when pressing on surfaces in the coarse range. Discrimination was better for sliding than pressing in the fine but not the coarse range. In contrast, tangential force fluctuations during sliding were strongly related to roughness judgment accuracy.

Highlights

Roughness perception through fingertip contact with a textured surface can involve spatial and temporal cues from skin indentation and vibration respectively
In this paper we examine the relation between normal force and normal and tangential force and roughness discrimination performance in a 2-interval forced choice (2-IFC) paradigm where each trial includes
The average proportion of trials where the participant correctly reported which of the two stimuli on a trial was rougher is shown in Fig. 2(a,b) as a function of the difference in groove width between the standard and the comparison stimuli

Summary

Introduction

Roughness perception through fingertip contact with a textured surface can involve spatial and temporal cues from skin indentation and vibration respectively. Given differing cues to roughness from pressing or sliding the finger over a surface, it might be expected that contact forces normal and tangential to the surface might have contrasting effects in pressing and sliding on any relation with roughness discrimination accuracy.

Results

Conclusion