Humanoid robots laughing in response to a joke: Results of a video-based online survey

In this paper we present first results of two online surveys designed to investigate, which kind of recorded, human laughter appears to be most naturally to a human observer in combination with body movements of two different humanoid robots. As humans most often laugh within a social context [1, 2], which in turn influences the style of their laughter, we told the participants of both surveys that our humanoid robots would start laughing in response to a joke. A description of this situational context together with written instructions was presented online before each robot’s laughter had to be judged based on the pairwise sequential presentation of a total of six short video clips per robot. To check for a possible interaction of a robot’s outer appearance and the perceived naturalness of its laughter, we used two different human-sized, humanoid robots, namely, Robovie II [3] and Robovie R2 [4]. Furthermore, their laughter was followed by the Japanese exclamation “Ariehen!” (meaning “unbelievable”), which was rendered by a speech synthesizer. For the laughter sounds we manually chose five female, Japanese laughter samples originating from dyadic smalltalk recordings [5]. The restriction to female laughter for both robots was motivated, first, by the robot’s speech synthesis being based on a female voice as well and, second, by our belief that there were still enough variations possible for realizing laughter. Because childlike laughter seemed to fit to our humanoid robots as well, we pitched one sample by 25% (without changing its duration) to produce an artificial, more childlike laughter. These six laughter samples were systematically combined with videos of the two robots, in which they both performed the same movements: after they listened to the last sentence of the joke and while the laughter samples were played, they moved their heads backward to the left and lifted their arms resembling an “open-hand” gesture. With finishing their laughter they moved back into their initial positions looking straight into the camera with their arms next to their bodies while saying “Ariehen!”.