Tears improve the accuracy of conveying sadness in robots: Interaction with facial expressions

Abstract

This study aimed to examine the function of tears in conveying sadness using controlled robot baseline facial expressions, compare this function with facial expressions, and clarify the interaction effects between facial expressions and tears. Images of robots created using three-dimensional computer graphics were used as visual stimuli. The robots’ expressions included neutral and sad patterns, both with and without digital tears, resulting in four patterns. The participants were shown the images of the robots and asked to rate how strongly they thought the robots were expressing the six basic emotions and calm. Results confirmed that tears increased the intensity rating of sadness, and the combination of tears and sad expressions was most effective at conveying sadness. Furthermore, the evaluations of sad expressions without tears and neutral expressions with tears were nearly identical. These findings suggest that giving robots the capacity to cry may be more effective at conveying sadness than introducing facial expressions alone.