Personal Space in Human-Robot Interaction at Work: Effect of Room Size and Working Memory Load

Leichtmann, Benedikt; Lottermoser, Albrecht; Berger, Julia; Nitsch, Verena · 2022 · Crossref

DOI: 10.1145/3536167

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Summary

This study addresses a critical research gap in human-robot interaction (HRI) regarding the influence of contextual factors on personal space. While previous literature focused on human and robot-specific traits, it largely neglected environmental and task-related variables. Motivated by the need for socially acceptable robot navigation in industrial settings, the authors investigated how room size and working memory load affect a human’s comfort distance toward an approaching mobile robot. The study also aimed to identify the psychological mechanisms—specifically arousal and perceived control—that mediate these effects, thereby providing theoretical grounding for adaptive path-planning algorithms. The researchers conducted a preregistered laboratory experiment using a 3 × 2 within-subject design with 72 participants. Participants were approached by a mobile manufacturing robot in a simulated warehouse corridor. Room size was manipulated across three levels: large (190 cm width, no rear obstacle), medium (110 cm width, no rear obstacle), and small (110 cm width, rear obstacle blocking escape). Working memory load was manipulated by assigning participants either no secondary task or a cognitively demanding backward counting task. The primary dependent variable was comfort distance, measured as the distance at which participants signaled the robot to stop. Mediating variables included emotional arousal and perceived control, assessed via questionnaires after each trial. Contrary to initial hypotheses, room size and working memory load did not have significant direct effects on comfort distance. However, mediation analysis revealed significant indirect effects. Smaller room sizes and higher working memory loads significantly increased participants’ emotional arousal and decreased their perceived control. These internal states, in turn, led to larger comfort distances. Specifically, higher arousal and lower control were associated with increased distancing behavior. Additionally, the study found that comfort distances decreased with repeated exposure, reducing by approximately 1.85 cm per encounter as participants gained experience with the robot. The findings imply that contextual stressors influence personal space through psychological mediators rather than direct spatial constraints. For HRI applications, this suggests that robots should adapt their path planning to maintain larger distances in environments that induce high arousal or low perceived control, such as narrow spaces or during cognitively demanding tasks. By accounting for these indirect effects, robot navigation systems can better avoid causing discomfort or withdrawal behaviors in human workers. The study underscores the importance of integrating psychological theories, such as compensatory control models, into HRI research to explain the underlying mechanisms of distancing behavior.

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