“Too Crowded for a Robot?”: Modeling Human Acceptance Criteria for Elevator-Riding Robots

Paper Title

“Too Crowded for a Robot?”: Modeling Human Acceptance Criteria for Elevator-Riding Robots

Publication Info

• Topic area: Human–robot interaction in shared elevator environments.
• Keywords: Elevator robots, human acceptance, spatial norms, Robot Boarding Area, congestion, proxemics, accessibility, VR experiments, interaction design, skip-boarding strategies.

Background and Problem

• Problem / challenge: Existing studies on human–robot interaction (HRI) in elevators focus on navigation and positioning but fail to identify concrete criteria for robot boarding feasibility. Crowding and spatial conflicts remain unresolved challenges.
• Significance: Elevators are essential shared infrastructure in high-rise buildings, and efficient robot use can reduce delays and improve service. However, socially unacceptable robot behavior can cause discomfort and rejection, limiting deployment.
• Motivation and related work: Prior research highlights proxemics, social norms, and polite interaction cues as critical for acceptance but does not address dynamic boarding decisions. This paper builds on these insights to formalize spatial thresholds and adaptive strategies for elevator-riding robots.

Solution

• Proposed approach: Introduce the Robot Boarding Area (RBA)—a designated entry zone for robots—and model human acceptance criteria based on spatial availability and congestion. Evaluate adaptive skip-boarding strategies.
• Novelty:
  1. Formalization of spatial thresholds for robot boarding feasibility.
  2. Empirical evidence showing how RBA occupancy and elevator congestion affect acceptance.
  3. Identification of skip-boarding strategies as a socially acceptable alternative under crowded conditions.
  4. Practical design principles for robot behavior and communication in shared elevator environments.
• Procedure and key techniques:
  • Define the RBA geometry based on robot footprint and proxemic margins.
  • Conduct two studies: an online survey (N=365) to test spatial acceptance criteria and a VR experiment (N=30) to evaluate boarding strategies and interaction modalities.
  • Analyze acceptance using mixed models and repeated-measures ANOVA, focusing on congestion, RBA occupancy, and communication effects.

Results

• Concrete findings:
  • Acceptance sharply declines when the RBA is occupied, with odds of non-acceptance increasing by factors of 4.16–43.00 depending on conditions.
  • Skip-boarding is preferred under high congestion (9 occupants), improving satisfaction (+1.12) and acceptance (+1.13) compared to boarding.
  • Voice interaction improves clarity and perceptions of competence, safety, and comfort but does not compensate for blocked spatial conditions.
• Advantage over baselines:
  • Skip-boarding strategies outperform forced boarding in crowded scenarios, signaling social sensitivity and reducing discomfort.
  • Voice + text interaction enhances understanding and trust compared to text-only communication.
• Experiments / evaluation:
  • Study 1 (online survey): Tested spatial acceptance criteria across 44 elevator scenarios with varying occupancy and RBA conditions.
  • Study 2 (VR experiment): Examined boarding vs. skip strategies and interaction modalities under controlled congestion levels (5, 7, 9 occupants).
  • Metrics: Satisfaction, acceptance, perceived competence, safety, comfort, and understanding of robot intent.
• Limitations and future work:
  • Limited demographic diversity (single company sample) and single robot type.
  • VR lacks subtle real-world social cues; field studies are needed for ecological validation.
  • Future work should refine borderline rules for 6 occupants, explore multimodal interaction design, and test generalizability across diverse robot sizes and environments.

Summary

This study formalizes human acceptance criteria for elevator-riding robots, introducing the Robot Boarding Area (RBA) as a key spatial determinant. Empirical evidence shows that RBA occupancy and elevator congestion significantly reduce acceptance, while skip-boarding strategies improve satisfaction under crowded conditions. Voice interaction enhances clarity and trust but cannot compensate for blocked space. Practical design principles—conservative boarding thresholds, selective communication, and adaptive behavior—guide socially acceptable robot deployment. Future research should validate findings across diverse demographics and real-world settings, refine spatial rules, and explore multimodal interaction strategies.