A Matter of Height: The Impact of a Robotic Object on Human Compliance

2025-09-19

AI Summary

This study investigates whether robot height—akin to human stature—influences human compliance, challenging the assumption that taller agents inherently convey greater authority. Method: A modular, non-anthropomorphic mobile service robot was deployed in ecologically valid field experiments; robot height was systematically manipulated (95 cm vs. 132 cm), and participant compliance was measured via voluntary completion rates of an extended questionnaire. Contribution/Results: Contrary to human social norms, the shorter robot (95 cm) elicited significantly higher compliance—a counterintuitive finding suggesting that anthropomorphic social heuristics do not directly transfer to human–robot interaction. The study demonstrates the necessity of empirically grounded, robot-specific modeling of physical morphology’s social effects. Through rigorous experimental control and ecological validity, it provides novel empirical evidence bridging robotics morphology and behavioral compliance research, thereby advancing theoretical frameworks and practical design guidelines for socially intelligent robots.

Technology Category

• Intelligent Robots: Human-Robot Interaction
• Humans and AI: Interaction Techniques and Devices
• Cognitive Modeling & Cognitive Systems: Social Cognition And Interaction

Application Category

• Responsible Web: Machine-in-the-loop, human agency and autonomy
• User Modeling, Personalization and Recommendation: Practical large-scale studies of user experience
• Economics, Online Markets and Human Computation: Data quality aspects of human-annotated datasets

Abstract

Robots come in various forms and have different characteristics that may shape the interaction with them. In human-human interactions, height is a characteristic that shapes human dynamics, with taller people typically perceived as more persuasive. In this work, we aspired to evaluate if the same impact replicates in a human-robot interaction and specifically with a highly non-humanoid robotic object. The robot was designed with modules that could be easily added or removed, allowing us to change its height without altering other design features. To test the impact of the robot's height, we evaluated participants' compliance with its request to volunteer to perform a tedious task. In the experiment, participants performed a cognitive task on a computer, which was framed as the main experiment. When done, they were informed that the experiment was completed. While waiting to receive their credits, the robotic object, designed as a mobile robotic service table, entered the room, carrying a tablet that invited participants to complete a 300-question questionnaire voluntarily. We compared participants' compliance in two conditions: A Short robot composed of two modules and 95cm in height and a Tall robot consisting of three modules and 132cm in height. Our findings revealed higher compliance with the Short robot's request, demonstrating an opposite pattern to human dynamics. We conclude that while height has a substantial social impact on human-robot interactions, it follows a unique pattern of influence. Our findings suggest that designers cannot simply adopt and implement elements from human social dynamics to robots without testing them first.

Problem

• Investigating how robot height affects human compliance
• Comparing tall versus short robotic object persuasion effectiveness
• Testing if human height social dynamics apply to robots

Innovation

• Modular robot design for height adjustment
• Comparing compliance between short and tall robots
• Non-humanoid robot used in social interaction experiment