Emotional Expression in Simple Line Drawings of a Robot's Face Leads to Higher Offers in the Ultimatum Game.

Chikara Takeuchi,Kazunori Terada

doi:10.3389/fpsyg.2017.00724

Abstract

In the present study, we investigated whether expressing emotional states using a simple line drawing to represent a robot's face can serve to elicit altruistic behavior from humans. An experimental investigation was conducted in which human participants interacted with a humanoid robot whose facial expression was shown on an LCD monitor that was mounted as its head (Study 1). Participants were asked to play the ultimatum game, which is usually used to measure human altruistic behavior. All participants were assigned to be the proposer and were instructed to decide their offer within 1 min by controlling a slider bar. The corners of the robot's mouth, as indicated by the line drawing, simply moved upward, or downward depending on the position of the slider bar. The results suggest that the change in the facial expression depicted by a simple line drawing of a face significantly affected the participant's final offer in the ultimatum game. The offers were increased by 13% when subjects were shown contingent changes of facial expression. The results were compared with an experiment in a teleoperation setting in which participants interacted with another person through a computer display showing the same line drawings used in Study 1 (Study 2). The results showed that offers were 15% higher if participants were shown a contingent facial expression change. Together, Studies 1 and 2 indicate that emotional expression in simple line drawings of a robot's face elicits the same higher offer from humans as a human telepresence does.

Highlights

There has been increasing interest and progress in robotic emotional expressions
We investigated whether expressing emotional states using a simple line drawing to represent a robot’s face can serve to elicit altruistic behavior from humans
The Mann–Whitney U-tests, U = 18.5, z = 3.46, p < 0.001, revealed that ratings for perceiving emotions from the line drawing were significantly higher in the change of facial expression condition than in the static face condition

Summary

Introduction

There has been increasing interest and progress in robotic emotional expressions. There have been studies on the effect of robotic emotions on human behavior (Cassell and Thorisson, 1999; Bickmore and Picard, 2005; Leyzberg et al, 2011); these focused on the taskoriented effects of emotions. A long-term experiment conducted by Bickmore and Picard (2005) showed that an agent with relational behavior, including social-emotional responses, contributed to increasing participants’ positive attitude about exercise. While these studies revealed that robots with emotions positively affect human behavior, the nature, and essential function of these emotions have not been discussed. We focused on the social functional aspect of emotions and experimentally investigated the effect of emotional expression as depicted through a simple line drawing of a face on human economic behavior

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