This study employed a three-week between-subjects design to explore the role of SAR in habit formation, comparing two conditions: robot-assisted and screen-only. Participants chose an exercise-related behaviour to develop into a habit and performed it in response to a daily cue defined through implementation intentions. Participants were fully informed that the technology aimed to influence their behaviour. The primary variable of interest was the SAR's presence and its influence on habit formation.

In this study, the robot was not there to guide a participant through the process of performing a behaviour, nor was it there to cue a behaviour. Instead, the robot was present to provide a consistent reminder and self-reflection to participants to perform the behaviour, and the physical embodiment enabled the participant to feel like they were having a conversation with a social agent whose expressivity would adjust based on the responses that the participant provided.

Participants were randomly assigned to one of two conditions:

• Robot-assisted Condition: Participants interacted daily with the SAR for reminders and check-ins. The robot provided embodied social interaction through emotional expressivity, conversational engagement, and motivational interviewing techniques.
• Screen-only Condition: Participants interacted daily with an identical dialogue and reminder structure presented through a digital interface without physical embodiment. This condition served as a comparison to isolate the effect of physical embodiment provided by the SAR.

Figure 1 illustrates the overall study procedure. All participants followed the same initial steps but diverged during the study period into either the robot-assisted or screen-only condition before converging again for the post-study questionnaire and interview.

The study comprised four phases:

• Study qualification: to ensure participants meet the requirements of the study.
• Priming and set up: Introductory session, establishing implementation intentions, and training participants on their assigned interaction method (robot or screen).
• Study period: 21-day period with minimal external interference except necessary communication and system troubleshooting.
• Post study: Final questionnaires and interviews assessing the experience, perceptions, and effectiveness of the intervention.

Figure 1: Visual representation of the study procedure. Participants completed onboarding and priming sessions before being randomly assigned to either the robot-assisted or screen-only condition for the 21-day study period. The two conditions converged again for the final post-study interview and questionnaires.