Further Experiments to Investigate the Influence of Robot Motions on Human Impressions

This paper investigates human impressions of the robot´s reaching motion based on psychophysiological experiments. There has been an increasing development of robots that move in the immediate vicinity of humans. It is important to ensure the security and relief of humans in the presence of robots. In our previous works, we employed heart rate variabilities, skin potential responses, and skin conductance responses (SCR) to investigate the influence of robot motion on human impressions. The results of several experiments showed that there was a modality effect, that is, the blocking out of the actuation noise and sight coming from robots tended to decrease the sympathetic nerve system (SNS) response. In this paper, we performed further experiments to investigate the modality effect and the long-term effect on human impressions based on SCR analysis and subjective ratings. The long-term effect implied a variation of response to robot motion over a long period. When the same stimuli are presented to humans, their responses to the stimuli tend to attenuate gradually. This phenomenon is known as habituation. In our experimentation (Hanajima et al., 2005), the subjects were asked to engage in two successive sets of the experiment for two months. We found two kinds of habituation in the data, the variation in a day and the variation between days. We defined the short-term variation as the former and the long-term variation as the latter. By comparing them, the long-term effect was investigated. As a result, we confirmed the same modality effect as illustrated in previous works. We also observed significant differences in the short-term and long-term variation from the SCR analysis. In the analysis of subjective ratings, the significant difference in the long-term variation was observed in more subjects than in the short-term variation. This suggested that the negative mental impression of the subjects to robot motion decreased as time passed