Is two cuter than one? number and relationship effects on the feeling of kawaii toward social robots.

Kawaii, which is a Japanese word that means cute, lovely, and adorable, is an essential factor in promoting positive emotions in people. The characteristics of a target's appearance that induce such feelings of kawaii have been thoroughly investigated around the notion of Konrad Lorenz's famous baby schema. Such knowledge has been exploited to design the appearance of commercial products to increase their social acceptance and commercial appeal. However, the effects of the number of targets and showing their mutual relationships (like friendship) have not been investigated in the context of kawaii. Therefore, in this study, we conducted three web-based experiments and focused on how such factors contribute to feelings of kawaii toward social robots. In Experiment 1, the feelings of kawaii toward static images of targets were compared when they appeared alone or with another target: persons (twin boys/girls), non-human objects (cherries), and social robots. The results showed that the feeling of kawaii was stronger for two targets that displayed a mutual relationship (e.g., looking at each other and/or making physical contact) than for one target alone and for two-independent targets. In Experiment 2, these findings were replicated using video clips of robots. Two-related targets were rated as more kawaii than two-independent targets or a single target. These two experiments consistently show the advantage of multiple robots that display their mutual relationship for enhancing the viewer's feeling of kawaii. Experiment 3 examined the effect of the number of robots (from one to ten) and found that two robots induced the strongest feeling of kawaii. These results indicate that not only the physical characteristics of a target itself but also the number of targets and their perceived relationships affect feelings of kawaii.