The Effectiveness of a Digital Mindfulness Nudge Intervention on Well-Being, Cognitive, and Academic Outcomes in College Students

Rumination was measured using the 10-item Ruminative Responses Scale (Treynor et al., 2003), which assessed one's tendency to engage in repetitive and passive focus on symptoms of distress as well as their causes and consequences. Participants rate how frequently they engage in each response (e.g., "Think 'What am I doing to deserve this?'") on a 4-point Likert scale ranging from 1 (Never) to 4 (Always). Total scores will be computed by averaging the responses, with higher scores indicating greater rumination.

Depressive symptoms will be measured using the Centre of Epidemiologic Studies Depression Scale, 10-item revised version CES-D-R 10 (Andresen et al., 1994). Participants will respond to 10 items (e.g., "I felt that everything I did was an effort.") taking into account the past two weeks on a 4-point scale (1 = Rarely or none of the time, 4 = All of the time). Higher scores indicate higher levels of depressive symptomatology.

State anxiety will be assessed using the 6-item Spielberger State-Trait Anxiety Inventory STAI-6 (Marteau \& Bekker, 1992). Six items (e.g., "I was tense these past 2 weeks.") will be rated from 1 (Not at all) to 4 (Very much so) and averaged for a composite score. Higher scores indicate greater levels of anxiety.

Stress will be evaluated using the 4-item Perceived Stress Scale PSS-4 (Cohen et al., 1983). Participants will rate items such as "How often have you felt difficulties piling up so high that you could not overcome them?" on a 0 to 4 scale (0 = Never to 4 = Very often). Higher scores indicate higher levels of perceived stress.

Positive affect will be measured using the Circumplex Model of Affect (Russell, 1980). Participants will rate feelings such as 'Pleasant', experienced over the past two weeks.

Negative affect will be measured using the Circumplex Model of Affect (Russell, 1980). Participants rated feelings such as 'Irritable', experienced over the past two weeks.

Life satisfaction will be measured using the Satisfaction with Life Scale (SWLS) (Diener et al., 1985). Participants will rate five items (e.g., "In most ways, these past 2 weeks have been close to ideal") on a 7-point scale (1 = Strongly disagree to 7 = Strongly agree). Scores will be averaged and higher scores will indicate higher life satisfaction.

Productivity was assessed using five items drawn from the Task Performance subscale of the Individual Work Performance Questionnaire (IWPQ) (Koopmans et al., 2013; Koopmans et al., 2014). Participants will rate each item on a 0 to 5 scale (0 = Seldom, 5 = Always) for the past 2 weeks. Sample items include "I kept in mind the work result I needed to achieve" or "I managed my time well". The score will be computed as the mean of the five items, with higher scores indicating higher self-reported task performance.

Procrastination will be assessed using six items from the Irrational Procrastination Scale (Steel, 2002), such as "When I should be doing one thing, I did another." Participants will respond on a 1-5 scale, and higher scores indicate higher levels of procrastination.

Implementation Intention and Goal Progress were assessed using two face-valid items on a 5-point Likert scale (1 = Strongly disagree to 5 = Strongly agree). The implementation Intention question was "In the past 14 days, I have taken steps to achieve my goals for the month" while the goal progress question was "In the past 14 days, I have seen progress toward my goals for the month". Higher scores indicate greater implementation of intentions and greater progress toward monthly goals, respectively.

Study engagement will be measured using the 9-item Study Engagement Inventory (Salmela-Aro \& Read, 2017), which measures students' energy, dedication, and absorption in their studies. Participants will rate items such as "When studying, I felt bursting with energy" based on their experiences over the past three weeks. Responses will be given on a 6-point Likert scale ranging from 1 (Completely disagree) to 6 (Completely agree). Higher scores indicate greater levels of academic engagement.

Study burnout will be measured using the 9-item Study Burnout Inventory (Salmela-Aro \& Read, 2017), which assesses students' exhaustion, cynicism, and inadequacy in relation to their academic work. Participants will indicate how well each item describes their experiences over the past two weeks (e.g., "I felt overwhelmed by studying") on a 6-point Likert scale ranging from 1 (Completely disagree) to 6 (Completely agree). Scores were computed by averaging all items, with higher scores indicating greater academic burnout.