Social bonding through expressed needs: Insights from an identity-shape matching task

This study advances understanding of human-robot social bonds using an identity-shape matching task, where participants associated geometric shapes (circle, square, triangle) with identities (best friend, robot partner, stranger) and response times for matched pairs indicated processing advantages. Across three sets of experiments (1A–1C, 2A–2B, 3A–3B), we tested whether partner-advantage effects generalize to human–robot interaction (1A–1C), whether robots’ functional assistance enhances human–robot partnership and elicits friend-like processing advantages (2A–2B), and whether a robot’s need for human help further strengthens social connectedness (3A–3B). Experiments 1A–1C demonstrated that brief encounters with a single robot, without collaboration or physical presence, elicited partner-advantage effects, though less pronounced than for best friends. This effect was maintained in Experiments 2A–2B when the robot provided functional assistance, irrespective of its physical presence. Uniquely, Experiments 3A–3B revealed that the robot expressing needs without companionship was perceived as socially distant, like a stranger, but when expressing minor needs with reciprocal companionship, it achieved perceptual prioritization comparable to best friends. These findings validate the identity-shape matching task as a robust method to quantify human-robot relationships and highlight the unique role of expressed needs with companionship in fostering friend-like social bonds. • Identity-shape matching task objectively quantifies human-robot relationships. • Brief robot encounters without collaboration or presence elicit partner-advantage. • Functional robot assistance fosters partner- but not friend-level bonds. • A robot expressed needs with companionship enable a friend-like advantage effect.