How much distance do humans keep toward robots? Literature review, meta-analysis, and theoretical considerations on personal space in human-robot interaction

With the development of mobile robots, research on interpersonal distances grew by a new body of research introducing new opportunities to environmental psychology. In this review, an overview of the literature on interpersonal distances focusing on human-robot interaction is given. Findings on the most prominent factors are summarized and discussed with respect to findings from distancing in human-human interaction and theoretical considerations. Additionally, meta-analyses were performed to gain new insights based on data of k = 27 studies including a total of N = 1299 participants. However, results did not show any meaningful effects for gender, robot appearance or whether one is active or passive in the approach. Most studies lack a theoretical foundation and have methodological weaknesses, including low statistical power or questionable research practices, leading to a high false-positive rate or overestimated effect sizes. Solutions such as pre-registration, higher sample sizes, transparency and a more careful theoretical underpinning based on models of human spacing behavior are discussed. Psychologists are encouraged to support research on human-robot interaction in this respect.