Behavioral Design Focusing on Personal Distance to Elicit Attachment to Pet Robots
Authors: Jupiter Guard Yusuke , Yamamoto Keiko , Shibuya Yu 
Published: October 2023

What is the difference between a companion animal and a pet robot? In recent years, many pet robots with the theme of healing have been proposed in Japan. Although those pet robots are designed in various ways to be loved by humans, the number of pet robot owners is still far fewer than that of companion animal owners. This is partly because pet robots still cannot withstand long-term use because their interactions become obsolete at an early stage.Therefore, for the long-term use of pet robots, this research aims to build a long-term relationship between owners and pet robots by eliciting attachment to the pet robot from its owner, and to realize interactions that will prevent boredom with the pet robot.In particular, this paper focuses on the pet robot's “personal distance”. We evaluate whether the pet robot can elicit the owner’s attachment to the pet robot by shortening the personal distance as it interacts with its owner over a longer period.The experiment lasted for 14 days and involved 16 participants. The participants wore HMDs and observed the robot on the stereoscopic display during a certain period each day. Robots which behaved in 4 different patterns were presented, 3 of which shortened the personal distance each day, i.e., the robot gradually approached the participant each day, and the remaining 1 pattern is the one which the personal distance was constant and short, i.e., the robot always stayed at a close distance. The three types of robots that shortened their personal distance day by day were those that approached the participant remarkably in the first half of the experiment, those that approached the participant remarkably in the second half of the experiment, and those that approached the participant gradually and to a certain degree throughout the experiment.The participants were asked to answer a daily questionnaire to measure the degree of attachment they felt toward each robots daily. At the end of the experiment, participants were asked which robot they liked best.The results showed that the attachment scores of the robot with constant and short personal distance were significantly higher than those of the other robots for each of the 14 days, but the scores did not change significantly throughout each day of the experiment. On the other hand, among the robots whose personal distance varied, the evaluation value tended to increase throughout the experiment for the robot that approached the participant remarkably in the first half of the experiment. In addition, the results of the questionnaire asking which of the robots the participants liked best, showed the robot that approached the participant remarkably in the first half of the experiment was the most preferred among the four types of robots.These results suggest that by lengthening the experiment period, the attachment scores of the robot that approached the participant remarkably in the first half of the experiment might exceed that of the robot whose personal distance was constant and short, and elicit the owner's attachment to the robot.