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Accepted for/Published in: JMIR Aging

Date Submitted: Jan 11, 2026
Date Accepted: Jun 25, 2026

The final, peer-reviewed published version of this preprint can be found here:

The Influence of Robot Facial Expression and Inclusion Behavior on Rapport and Trust in Older Adults: Mixed-Factorial Experimental Study

Yueh HP, Lin KC, Lin W

The Influence of Robot Facial Expression and Inclusion Behavior on Rapport and Trust in Older Adults: Mixed-Factorial Experimental Study

JMIR Aging 2026;9:e91235

DOI: 10.2196/91235

PMID: 42456153

Warning: This is an author submission that is not peer-reviewed or edited. Preprints - unless they show as "accepted" - should not be relied on to guide clinical practice or health-related behavior and should not be reported in news media as established information.

Robot Facial Expression and Inclusion Behavior Influence Rapport and Trust in Older Adults: Experimental Study

  • Hsiu-Ping Yueh; 
  • Kuang-Chi Lin; 
  • Weijane Lin

ABSTRACT

Background:

The WHO framework for healthy ageing emphasizes that the capacity to establish and sustain relationships is a vital component of functional ability. Social robots offer valuable support for this relational aspect, although their effectiveness is contingent upon the quality of the interactions. While it is established that facial expressions and inclusive behaviors can influence rapport-building, the combined effects of these elements on older adults remain unexamined.

Objective:

This study aimed to investigate the main and interaction effects of robot facial expression (happy vs. unhappy) and interaction style (inclusive vs. exclusive) on the development of rapport between social robots and older adults residing in the community.

Methods:

A 2×2 factorial experimental design was employed in this study, involving 53 community-dwelling older adults (mean age, 70.57 years; SD, 4.27; 85% female). Participants engaged in a gamified interaction known as "Radish Squat," featuring two humanoid robots that displayed various combinations of facial expressions and interaction styles. The inclusive robot designated participants 75% of the time, whereas the exclusive robot did so an average of 25% of the time. Dependent measures included robot acceptance, rapport, rapport expectation (conversation partner and togetherness subscales), and trust. Behavioral designation frequencies were recorded throughout the gameplay. A mixed-design repeated measures ANOVA was conducted to examine both main and interaction effects.

Results:

Facial expression had significant effects on acceptance, rapport, conversation partner expectations, togetherness expectations, and trust. Interaction style also significantly affected rapport and the subscales related to rapport expectation. Importantly, significant interaction effects were observed for both rapport and trust, particularly in exclusive interaction conditions, where the impact of facial expressions was intensified. Interestingly, older adults showed a preference for the exclusive robot over the inclusive robot, with qualitative data suggesting the use of fairness-based turn-taking strategies.

Conclusions:

Positive facial expressions and inclusive interaction behaviors significantly enhance rapport, with their effects working synergistically. The observation that older adults often respond to exclusive robot behavior by assigning it more frequently suggests they perceive robots as social entities worthy of equitable treatment. These findings provide valuable evidence-based guidelines for designing social robots that support the relational aspects of healthy ageing.


 Citation

Please cite as:

Yueh HP, Lin KC, Lin W

The Influence of Robot Facial Expression and Inclusion Behavior on Rapport and Trust in Older Adults: Mixed-Factorial Experimental Study

JMIR Aging 2026;9:e91235

DOI: 10.2196/91235

PMID: 42456153

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