How about laughter? Perceived naturalness of two laughing humanoid robots

As humanoid robots will have to behave socially adequate in a future society, we started to investigate laughter as an important para-verbal signal influencing relationships among humans quite easily. As a first step we investigate, how humanoid robots might laugh within a situation, which is suitable for laughter. Given the variety of human laughter, do people prefer a certain style for a robot's laughter? And if yes, how does a robot's outer appearance affect this preference, if at all? Accordingly, we combined six recordings of female laughter with body movements for two different humanoid robots with the aim to evaluate their perceived naturalness using two types of video-based surveys. We not only found that people indeed prefer one type of laughter when being forced to choose, but the results also suggest significant differences in the perceived naturalness of laughter with regard to the participant's cultural background. The outer appearance seems to change the perceived naturalness of a humanoid robot's laughter only on a global level. It is evident, however, that further research on this rather unexplored topic is needed as much as it promises to provide valuable means to support the development of social robots.