When Humanoids Are Too Much: Exploring the Utilitarian-Hedonic Balance in Household Robot Design

초록

Background Domestic robots have historically been developed along two separate trajectories: purely functional robots and purely social robots, with limited integration of both dimensions. While purely social robots have faced repeated commercial failures due to lack of utility, purely functional robots suffer from diminished long-term user engagement. This study addresses a critical gap in the pre-humanoid robot design space by investigating the optimal balance between utilitarian and hedonic interaction dimensions. Methods A household robot named Hobbi was designed using Research through Design methodology, capable of performing both utilitarian tasks (object delivery, Internet of Things(IoT) control) and hedonic interactions (greeting, dancing, emotional expressions). Five interaction scenarios were constructed by systematically varying the utilitarian-hedonic ratio (4S0U, 3S1U, 2S2U, 1S3U, 0S4U). A within-subjects video-based evaluation was conducted with 56 participants, who rated each scenario across hedonic, utilitarian, and overall satisfaction dimensions using 9-point Likert scales. Results An inverted U-shaped satisfaction pattern was confirmed, with the balanced condition (2S2U) yielding peak satisfaction (M = 6.75) and the purely hedonic condition (4S0U) producing the lowest scores (M = 5.65). Regression analyses revealed asymmetric synergistic effects: hedonic interactions significantly enhanced utilitarian satisfaction (β = 0.241, p < .001), while utilitarian interactions did not reciprocally enhance hedonic satisfaction (β = 0.051, p = .420). Appearance design preference strongly predicted overall satisfaction (r = 0.633, p < .001), whereas prior technology interest showed no significant relationship. Conclusions These findings support a “utilitarian-foundation, hedonic-enhancement” design principle for domestic robots, wherein functional reliability serves as the necessary base and social-expressive interactions amplify perceived quality. The asymmetric synergy suggests that even simple hedonic behaviors yield substantial returns on utilitarian satisfaction, offering practical guidance for cost-effective robot development targeting broad consumer markets.

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