Does mindfulness facilitate critical thinking?

Primary measures will be taken at baseline and following the end of the intervention. All of the measures except the Sternberg Working Memory Task will be presented using SurveyGizmo.

Halpern Critical Thinking Assessment (HCTA; Halpern, 2010)
The HCTA involves 25 real-world situations with closed and open questions based on these situations. These situations involve medical research, social policy analysis and other types of problems encountered in everyday life. Five domains of critical thinking are assessed using the HCTA: Verbal reasoning, argument analysis, thinking as hypothesis testing, likelihood and uncertainty, and decision-making and problem-solving. The test includes 5 sets of questions (one open and one closed) for each of these domains. The scoring guide provides answers for forced-choice questions while open-ended questions are graded according to specific grading prompts (for more detail see Dwyer, Hogan, & Stewart, 2012). Greater scores are awarded to more accurate and comprehensive answers and total scores can range from 0 to 194 (Halpern, 2010). The internal reliability of the HTCA tends to be adequate (Dwyer et al., 2012; Halpern, 2010).

Heuristics and Biases items (West, Toplak, & Stanovich, 2008)
This series of standard items assessing cognitive biases is included as there is evidence that these assess an aspect of critical thinking not captured by traditional measures (West et al., 2008). These items assess participants’ ability to deal with problems involving causal base rates, noncausal base rates, the law of large numbers, regression to the mean, the gambler’s fallacy, conjunctions, covariation, Bayesian reasoning, framing and probabilistic reasoning (for full details of the items see West et al., 2008). Each of these items will be scored as either correct (1) or incorrect (0). Though these are not representative of a unidimensional construct, it has been shown to be useful to aggregate scores on these items (West et al., 2008).

Five Factor Mindfulness Questionnaire (FFMQ; Baer et al., 2006)
This questionnaire assesses levels of dispositional mindfulness. The FFMQ includes 39 items which tap five facts of mindfulness: describing (i.e. labelling experience with words), observing (i.e. paying attention to sensations, thoughts and feelings), non-reactivity (i.e. noticing thoughts without emotionally responding to them), non-judgment (i.e. acceptance of thoughts and feelings) and acting with awareness (i.e. lack of distraction). It employs a 5-point Likert scale (e.g. 1 = never or very rarely true; 5 = very often or always true). This measure has demonstrated adequate internal consistency and construct validity (Baer et al., 2008).

Need for Cognition scale (Cacciopo, Petty, & Kao, 1984)
This unidimensional scale measures the extent to which individuals tend to engage in effortful cognitive activity (Cacciopo, Petty, & Kao, 1984). The scale includes 18 items which are rated on a 5-point Likert scale (e.g. 1 = extremely uncharacteristic of me; 5 = extremely characteristic of me). It has been extensively validated and has been found to have adequate reliability (Tolentino, Curry, & Leak, 1990).

Actively Open Minded thinking scale (Stanovich & West, 1997)
This scale assesses the extent to which individuals tend to approach information in an open and flexible manner as opposed to a rigid manner which leads to resistance to belief change. The scale includes 41 items and these are rated on a 6-point Likert scale (e.g. 1 = strongly agree; 6 = strongly disagree).

Objective measures of meditation adherence (no. of sessions initiated and completed and no. of minutes spent meditating) will be gathered through the Headspace app.

Secondary measures will assess effects on wellbeing in order to compare with previous studies employing Headspace and will be taken at baseline and follow-up. All of the measures except the Sternberg Working Memory Task will be presented using SurveyGizmo.

Sternberg working memory task (Sternberg, 1975)
This task is a measure of executive control of working memory. It involves memorising a series of letters and indicating, as quickly and accurately as possible, whether a probe was in this series or not.

Positive Affect and Negative Affect Schedule (PANAS; Watson & Clark, 1994)
This scale is the most widely-used instrument for assessing inter- and intra-individual differences in experiences of positive and negative emotion. The PANAS-X consists of 60 items. Each item describes a different feeling or emotion and the scale can be used to assess general levels of positive and negative affect by asking participants to indicate to what extent they felt each of these emotions over the past week using a 5-point Likert scale (e.g. 1 = very slightly or not at all; 5 = extremely). Psychometric evaluations tend to find good reliability for the positive and negative subscales (Simmons & Lehmann, 2012).

Warwick-Edinburgh Mental Wellbeing Scale (Tennant et al., 2007)
This is a 14-item scale of mental well-being covering subjective well-being and psychological functioning, in which all items are worded positively and address aspects of positive mental health. The scale is scored by summing responses to each item answered on a 5-point Likert scale. The minimum scale score is 14 and the maximum is 70. A high score reflects a high level of positive mental health and a low score reflects a low level of positive mental health (Stewart-Brown & Janmohamed, 2008).

Real World Outcomes Inventory (Butler et al., 2012)
This is a behavioural checklist focused on life outcomes from many domains ranging in severity from mildly negative (e.g., paying late fees for a movie rental) to severely negative (e.g., spending a night in jail). It was developed based in the Decision Outcomes Inventory (Bruine de Bruin et al., 2007). The version employed here is slightly adapted to ensure cultural relevance. Any items which do not fit the Irish context will not be used (e.g. got blisters from sunburn).

Manipulation checks
In week 2 and week 4 participants will complete short questionnaires assessing mindfulness meditation quality and task expectations, enjoyment and difficulty. These will be completed online, allowing participants to complete them at their convenience. Participants will be asked to complete these measures directly following a meditation session.

Practice Quality- Mindfulness questionnaire (Del Re et al., 2013)
This 6-item questionnaire assesses perseverance and receptivity during meditation. Perseverance is defined as the ability to continually redirect attention back to the focus of the meditation. Receptivity refers to the willingness to fully experience what is arising during the course of a meditation session. The items are presented alongside a percentage scale and participants are asked to indicate the percentage of time during their meditation session during which their experience reflected each of the item statements. This scale has been shown to fit a 2-factor structure and has demonstrated a predictive relationship between practice quality and improvements in psychological symptoms (Del Re et al., 2013)

Technology Acceptance Model questionnaire (TAM; Davis, 1993)
Items from the TAM assessing expectations, enjoyment and difficulty using the Headspace app will be presented to participants. The TAM is a widely-used measure of user acceptance of technology. The items on this scale are phrased as statements and are measured on a 5-point Likert scale (e.g. 1= strongly disagree; 5 = strongly agree).

Intervention Acceptability (Kirkpatrick et al., 2013)
Four items assessing satisfaction with the intervention were administered. Two questions using a 5 point Likert scale (e.g. 1 = very dissatisfied; 5 = very satisfied) will assess general satisfaction with the programme and satisfaction with the content of the guided sessions in particular. The next two questions require yes/no answers and relate to whether participants would recommend the programme and whether they felt it was worth their time. Questions like these have been used in previous research examining the acceptability of low-intensity online treatments and across a range of different age groups and health conditions (Kirkpatrick et al., 2013).