{"ID":6138254,"CreatedAt":"2026-07-09T01:07:32.349475501Z","UpdatedAt":"2026-07-11T13:15:01.920489011Z","DeletedAt":null,"paper_url":"https://arxiv.org/abs/2607.07390","arxiv_id":"2607.07390","title":"Communicative Efficiency of Single vs. Multi-Axis Robot Neck Motion","abstract":"Nonverbal communication through head and neck movement is fundamental to human social signalling, yet how robotic neck morphology translates motion into communicative information remains poorly understood. We present an information-theoretic framework characterising robot neck movement as a communication channel, quantifying information transmitted and energy expended across varied configurations. Using a robotic neck platform, we recorded 84 video stimuli spanning three rotational degrees of freedom (DoF), varying amplitude, acceleration, and frequency, measuring Shannon entropy of pixel-change signals alongside energy consumption. A perceptual study validated communicative interpretations of each motion. While humans typically engage one axis per gesture, robots are unconstrained by biological architecture, motivating tests up to 3 DoF. Yet communicative information peaks at two DoF and decreases at three despite rising energy cost, a phenomenon we term the morphological information bottleneck. Motion parameter effects were parameter-dependent, some additive, others non-linear. We introduce the Motor Information Space, a framework mapping entropy against energy to expose communicative efficiency across morphologies, in which the optimal configuration achieves 5.26 bits at competitive energy cost. Perception data further confirm multi-axis movements reduce clarity. These findings challenge the assumption that anatomical completeness improves robotic expressiveness, establishing a quantitative basis for morphological design in robots, especially humanoids.","short_abstract":"Nonverbal communication through head and neck movement is fundamental to human social signalling, yet how robotic neck morphology translates motion into communicative information remains poorly understood. We present an information-theoretic framework characterising robot neck movement as a communication channel, quant...","url_abs":"https://arxiv.org/abs/2607.07390","url_pdf":"https://arxiv.org/pdf/2607.07390v1","authors":"[\"Chapa Sirithunge\",\"Haewon Jeong\",\"Qinghua Guan\",\"Fumiya Iida\",\"Josie Hughes\"]","published":"2026-07-08T13:23:56Z","proceeding":"cs.RO","tasks":"[\"cs.RO\",\"cs.IT\"]","methods":"[]","has_code":false}