Nonverbal interactions are a key component of human communication. Since robots have become significant by trying to get close to human beings, it is important that they follow social rules governing the use of space. Prior research has conceptualized personal space as physical zones which are based on static distances. This work examined how preferred interaction distance can change given different interaction scenarios. We conducted a user study using three different robot heights. We also examined the difference in preferred interaction distance when a robot approaches a human and, conversely, when a human approaches a robot. Factors included in quantitative analysis are the participants' gender, robot's height, and method of approach. Subjective measures included human comfort and perceived safety. The results obtained through this study shows that robot height, participant gender and method of approach were significant factors influencing measured proxemic zones and accordingly participant comfort. Subjective data showed that experiment respondents regarded robots in a more favorable light following their participation in this study. Furthermore, the NAO was perceived most positively by respondents according to various metrics and the PR2 Tall, most negatively.

A follow up study involved finding out if there is any correlation between the robot's height and the method of approach focus across each proxemic zone based on the results obtained from our prior work. In addition, we conducted an user study to understand how interaction distance between a human and a robot changes with the change in the robot's physical configuration such as arm position (extended versus tucked in) and gaze (robot directly looking at the participant versus robot being distracted reading a newspaper). Data collected from this experiment was used to study the relationship between the physical configuration of the robot and preferred interaction distance. Subjective measures included human comfort and perceived safety. The results obtained through this study shows that robot's arm position and gaze behavior did have a significant effect in influencing measured proxemic zones. Subjective data showed that the experiment did have a short-term impact on the participants' opinion on the robot.

@mastersthesis{rajamohan2020factors,
  title={Factors Influencing The Human Preferred Interaction Distance},
  author={Vineeth Rajamohan},
  year={2020},
  month={May},
  url={https://scholarworks.unr.edu/bitstream/handle/11714/7462/rajamohan_unr_0139M_13199.pdf?sequence=1},
}

CHS: Small: Socially-Aware Navigation, National Science Foundation PI: David Feil-Seifer, co-PI: Monica Nicolescu, Amount: $500,000, Sept. 1, 2017 - May 31, 2022