Pleasant Stroke Touch on Human Back by a Human and a Robot

Abstract

Pleasant touching is an important aspect of social interactions that is widely used as a caregiving technique. To address the problems resulting from a lack of available human caregivers, previous research has attempted to develop robots that can perform this kind of pleasant touch. However, it remains unclear whether robots can provide such a pleasant touch in a manner similar to humans. To investigate this issue, we compared the effect of the speed of gentle strokes on the back between human and robot agents on the emotional responses of human participants (n = 28). A robot or a human stroked on the participants’ back at two different speeds (i.e., 2.6 and 8.5 cm/s). The participants’ subjective (valence and arousal ratings) and physiological (facial electromyography (EMG) recorded from the corrugator supercilii and zygomatic major muscles and skin conductance response) emotional reactions were measured. The subjective ratings demonstrated that the speed of 8.5 cm/s was more pleasant and arousing than the speed of 2.6 cm/s for both human and robot strokes. The corrugator supercilii EMG showed that the speed of 8.5 cm/s resulted in reduced activity in response to both human and robot strokes. These results demonstrate similar speed-dependent modulations of stroke on subjective and physiological positive emotional responses across human and robot agents and suggest that robots can provide a pleasant touch similar to that of humans.

Delivery of pleasant stroke touch via robot in older adults

“…We recruited 30 healthy older Japanese men (mean ± SD age, 72.0 ± 4.2 years) from a human resource center in Kyoto, Japan. As in the previous study (Ishikura et al, 2023 ), we recruited only male participants because variable touch effects have been reported across genders (Russo et al, 2020 ). We jointly analyzed data collected from 28 younger Japanese men (mean ± SD age, 23.1 ± 2.9 years) in the previous study (Ishikura et al, 2023 ) in which an identical experiment was conducted.…”

“…As in the previous study (Ishikura et al, 2023 ), we recruited only male participants because variable touch effects have been reported across genders (Russo et al, 2020 ). We jointly analyzed data collected from 28 younger Japanese men (mean ± SD age, 23.1 ± 2.9 years) in the previous study (Ishikura et al, 2023 ) in which an identical experiment was conducted. We calculated the demanded sample size using G*Power software ver.…”

“…We found that more than 50 participants were needed in total and tested 58 (30 older + 28 younger) participants. The younger data comes from the previous study (Ishikura et al, 2023 ). We obtained written informed consent from all participants for participation in this study as approved by the ethics committee of the Nara Institute of Science and Technology, Ikoma, Japan, and as consistent with the Declaration of Helsinki.…”

“…These speeds were expected to activate the C tactile (CT) system (1.0–10.0 cm/s), although the optimal speed can differ across different body regions (Ackerley et al, 2014 ). For both human and robot agents, the 8.5 cm/s stroking elicited more positive subjective (i.e., higher valence ratings) and physiological (i.e., reduced corrugator supercilii EMG) responses compared with the 2.6 cm/s stroking (Ishikura et al, 2023 ). The similarities in the speed-dependent modulations of touch across the agents imply that robots can provide a pleasant stroke touch like humans.…”

A study on robot force control based on the GMM/GMR algorithm fusing different compensation strategies

“…The control parameters of impedance control, such as stiffness and damping, require utilizing manual adjustment or trial and error, and the controller is insensitive to the uncertainty of the external environment. To adapt robots to the flexible environment of human skin, other scholars, such as Liu et al ( 2021 ), Khoramshahi et al ( 2020 ), Li et al ( 2020 ), Ishikura et al ( 2023 ), Huang et al ( 2015 ), and Stephens et al ( 2019 ) used adaptive algorithms and intelligent algorithms for optimizing the impedance control parameters. The skin, being a living tissue, has biomechanical properties, such as elasticity, viscoelasticity, non-linearity, and anisotropy (Joodaki and Panzer, 2018 ).…”