Modulating Multimodal Emotional and Social Perception of Huggable Robot Expressions Through Chest Haptics

Emotional and social expression are important dimensions of socially empathic human-robot interaction. In hug gable robot contexts, the chest is not only a stable bodily contact interface with strong affective relevance, but also a natural site for presenting haptic and auditory cues together. However, existing chest-haptic designs still focus mainly on physical tactile parameters or heartbeat-like patterns. Conversely, chest haptic patterns formed by different stimulation-location combinations over time may offer richer possibilities for multimodal expression and modulation. To explore this, we implemented a parameterizable 3×3 chest-mounted vibrotactile array on a huggable robot and constructed chest haptic patterns using path type and activation area as design parameters. We conducted two experiments. Experiment 1 examined how chest haptic patterns influenced the affective perception of emotional music. Experiment 2, under a fixed activation area setting, examined how the presence of chest haptics and different path conditions influenced the social emotional evaluation of verbal expressions with empathic intentions. The results showed that, in the emotional music context, chest haptic patterns influenced the direction of emotional rating shifts and showed more pronounced modulation effects under some music conditions. In the empathic speech context, the addition of chest haptics generally improved social-emotional evaluations. These findings provide empirical support for the use of chest haptic patterns in multimodal social-emotional expression, and offer guidance for the future development of huggable robots with richer emotional and empathic expression.