Mapping Embodied Affective Touch Strategies on a Humanoid Robot

2026-05-12

AI Summary

This study addresses the limited understanding of affective touch across the full body of humanoid robots and its modulation by embodiment. Leveraging an iCub robot equipped with distributed whole-body tactile sensors, 32 participants expressed eight emotions under three conditions: free touch, arms-only, and torso-only. Integrating tactile dynamics analysis, subjective reports, and social relationship perception assessments, this work provides the first systematic mapping of whole-body affective touch strategies. Results reveal a preference for socially accessible upper-body regions, with low-frequency touch zones exhibiting greater emotion specificity. Emotional differentiation relied primarily on motion features on the arms but on pressure features on the torso. Notably, approximately 30% of participants reported altered perceptions of their social relationship with the robot, and touch strategies did not directly transfer across different bodily constraints.

Abstract

Affective touch in human-robot interaction is shaped not only by emotional intent, but also by robot embodiment, including touch location, physical constraints, and perceived agency or social role. Existing HRI studies typically focus on one or two isolated body parts, limiting understanding of how affective touch generalises across the full humanoid body. We present a study with 32 participants interacting with the iCub robot, which is equipped with full-body distributed tactile sensors. Participants expressed eight emotions under three conditions: free touch, arm-only touch, and torso-only touch. Results show that body region and spatial constraints jointly shaped both touch location and dynamics. In free touch, participants preferred socially accessible upper-body regions, while less frequently touched areas showed stronger emotion-specific selectivity. Emotion-related variation was more evident in motion features for arm-only touch and pressure features for torso-only touch. Touch strategies also did not transfer directly between free and constrained conditions, even within the same coarse body region. Participants reported increased closeness to the robot after interaction, with around 30 percent reporting a change in perceived social relationship. Together, these findings show that affective touch expression is strongly body-region dependent and shaped by embodiment constraints.

Problem

• affective touch
• humanoid robot
• embodiment
• body region
• human-robot interaction

Innovation

• affective touch
• humanoid robot
• embodiment constraints
• full-body tactile sensing
• emotion expression