When Less Isn’t Less: Reducing DoF Does Not Weaken Robots’ Social Expressivity

Robots are becoming part of everyday life, where their success depends as much on social interaction as on task performance. While rich movement is often assumed to enhance that experience, minimal gestures can also elicit meaningful social interactions. This suggests that gesture design informed by fundamental human nonverbal cues may achieve comparable social expressivity with fewer degrees of freedom. We explored whether reducing a robot’s degrees of freedom alters the social experience by comparing interactions in two movement configurations: a Full-DoF condition and a Reduced-DoF condition. This comparison allowed us to evaluate whether increased movement capability contributes meaningfully to the quality of the social experience. Bayesian analyses consistently favored the null hypothesis, indicating no meaningful differences between the Full-DoF and Reduced-DoF conditions. These initial findings suggest that well-designed simple gestures can support a consistent social experience, challenging the assumption that greater movement capability should be automatically expected to enhance human–robot interaction.