Non-humanoid robotic communication: a cube’s expressive movements

Abstract

This study investigates how a simple cubic robot conveys basic human emotions through motion, offering insights into emotion expression in abstract robotic design. The study builds on the six basic emotions as proposed by Ekman, which include happiness, sadness, anger, fear, disgust, and surprise. The research examines how movements and their movement characteristics, such as direction, rhythm, and speed, contribute to emotional perception in human-robot interaction (HRI). Thirty undergraduate participants engaged in an exploratory, mixed-methods study where cube movement patterns were created and interpreted in a controlled setting. Results revealed that emotions such as happiness, anger, and sadness were more easily recognised. At the same time, fear, disgust, and surprise showed lower clarity scores, indicating challenges in conveying complex emotions through a geometric form. The study highlights the role of perceptual ambiguity and symbolic neutrality in fostering creative motion strategies and underscores the value of combining quantitative and qualitative insights. Findings suggest that basic geometric forms, such as cubes, can support emotional communication in robotics. However, different shapes and motion semantics may require further attention in future studies to explore them properly, thereby making the communication of simple forms more expressive.