Role of arm reaching movement kinematics in friction perception at initial contact with smooth surfaces

Role of arm reaching movement kinematics in friction perception at initial contact with smooth surfaces

Afzal, Naqash (University of New South Wales; Neuroscience Research Australia; Khalifa University of Science and Technology)
du Bois de Dunilac, Sophie (University College Dublin)
Loutit, Alastair J. (University of New South Wales; Neuroscience Research Australia)
Shea, Helen O. (University of Limerick)
Ulloa, Pablo Martinez (University College Dublin)
Khamis, Heba (University of New South Wales)
Vickery, Richard M. (University of New South Wales; Neuroscience Research Australia)
Wiertlewski, M. (TU Delft Human-Robot Interaction)
Redmond, Stephen J. (University College Dublin)
Birznieks, Ingvars (University of New South Wales; Neuroscience Research Australia)

2024

Abstract: When manipulating objects, humans begin adjusting their grip force to friction within 100 ms of contact. During motor adaptation, subjects become aware of the slipperiness of touched surfaces. Previously, we have demonstrated that humans cannot perceive frictional differences when surfaces are brought in contact with an immobilised finger, but can do so when there is submillimeter lateral displacement or subjects actively make the contact movement. Similarly, in, we investigated how humans perceive friction in the absence of intentional exploratory sliding or rubbing movements, to mimic object manipulation interactions. We used a two-alternative forced-choice paradigm in which subjects had to reach and touch one surface followed by another, and then indicate which felt more slippery. Subjects correctly identified the more slippery surface in 87 ± 8% of cases (mean ± SD; n = 12). Biomechanical analysis of finger pad skin displacement patterns revealed the presence of tiny (<1 mm) localised slips, known to be sufficient to perceive frictional differences. We tested whether these skin movements arise as a result of natural hand reaching kinematics. The task was repeated with the introduction of a hand support, eliminating the hand reaching movement and minimising fingertip movement deviations from a straight path. As a result, our subjects’ performance significantly declined (66 ± 12% correct, mean ± SD; n = 12), suggesting that unrestricted reaching movement kinematics and factors such as physiological tremor, play a crucial role in enhancing or enabling friction perception upon initial contact. (Figure presented.). Key points: More slippery objects require a stronger grip to prevent them from slipping out of hands. Grip force adjustments to friction driven by tactile sensory signals are largely automatic and do not necessitate cognitive involvement; nevertheless, some associated awareness of grip surface slipperiness under such sensory conditions is present and helps to select a safe and appropriate movement plan. When gripping an object, tactile receptors provide frictional information without intentional rubbing or sliding fingers over the surface. However, we have discovered that submillimeter range lateral displacement might be required to enhance or enable friction sensing. The present study provides evidence that such small lateral movements causing localised partial slips arise and are an inherent part of natural reaching movement kinematics.

force control
friction
hand
manipulation
motor control
perception
slip
tactile

http://resolver.tudelft.nl/uuid:e9d40f63-7a41-4571-a1f7-12f0948ba2db

https://doi.org/10.1113/JP286027

0022-3751

The Journal of Physiology

Institutional Repository

journal article

© 2024 Naqash Afzal, Sophie du Bois de Dunilac, Alastair J. Loutit, Helen O. Shea, Pablo Martinez Ulloa, Heba Khamis, Richard M. Vickery, M. Wiertlewski, Stephen J. Redmond, Ingvars Birznieks