Table 1.

Description of the components that make up the SCAP intervention.

Component	Structure	Activities/objectives	Theoretical targets
Intervention as a whole	–	- Provide content with high acceptability and feasibility - Provide an intervention distinct from existing programs to add interest and excitement - Foster HIV-related goal formation - Foster medication habit formation - Circumvent cognitive biases and heuristics - Motivate HIV viral suppression	Engagement, motivation (conscious and unconscious), habit formation, circumvent cognitive biases
Counseling session	<60 min, delivered by an interventionist to participants individually; guided by a manual	- Orient participants to the study - Communicate study ethos to foster engagement - Elicit participants' own HIV-related health goals and barriers to/facilitators of goals - Discuss habit formation - Introduce the TMQQ component and prize structure	Motivation (conscious) for HIV viral suppression
TMQQ	16 weeks in duration; an informational text message (TM) on HIV was sent once a week followed by a true/false quiz question (QQ) the next day	- Support engagement in the study over time - “Nudge” participants toward their HIV health goals, if any - Add interest and novelty to the intervention process - Participants earned 10 points for correct and 5 points for incorrect responses to the QQ (max. points 160)	Engagement; circumvent cognitive biases and heuristics; foster habit formation
Check-in contact	<30 min; conducted 8-weeks post enrollment	- Reinforce the main messages of the intervention - Demonstrate the prize wheel in a concrete fashion (with a practice spin and compensation up to $50) - Resolve any barriers to receiving TMs or responding to the QQs	Motivation; engagement
Lottery prize	Prize between $5 and $275 was allocated	- A prize wheel (similar to a roulette wheel) was spun to determine the prize amount - Prizes depended on (1) points earned in the TMQQ component, (2) whether HIV viral suppression was achieved, and (3) chance - Prize was intended to add interest and excitement to the process of achieving HIV-related goals - All participants received some level of prize	Motivation (unconscious); circumvent cognitive biases and heuristics