Do Adversarial Robots Increase Human Effort? Social Behavior in Human-Robot Competition

Abstract

In human-robot interaction, achieving a goal may require a robot to engage in competitive behaviors toward its human partner. In some cases, it is important for the robot to balance firmness with an amicable attitude to avoid causing discomfort to the user. In others, it might be necessary to push the user to act more assertively or competitively. In this work, we investigate whether a robot's competitive social behavior, operationalized through verbal and nonverbal cues, can influence humans' decision-making in a strategic game such as an auction. Participants competed in an English auction game against a humanoid robot, which displayed either an amicable or a confrontational behavioral profile, through verbal language and nonverbal gestures. Competitiveness was evaluated through behavioral outcomes and perceived robot attributes, with biometric measures derived from posture and facial expression analysis included as exploratory indicators. Results indicate that robot attitude significantly alters perceived warmth, competence, and discomfort, while confrontational behavior selectively enhanced game performance in individuals with higher baseline competitiveness, as revealed by a significant interaction between robot condition and competitive trait. No significant effects emerged in biometric indicators, suggesting that social framing primarily affects strategic and perceptual dimensions of competition.