Improvements in Critical Thinking Performance ...

Mindfulness DOI 10.1007/s12671-017-0789-8

ORIGINAL PAPER

Improvements in Critical Thinking Performance Following Mindfulness Meditation Depend on Thinking Dispositions Chris Noone 1

&

Michael J. Hogan 1

# Springer Science+Business Media, LLC 2017

Abstract Many claims have been made regarding the application of mindfulness meditation to the improvement of critical thinking skills, with some suggesting improved executive function as a mechanism. This study tests theoretical assumptions related to these claims. Sixty-five Irish university students took part in an active-controlled mixed factorial experiment designed to investigate the effects of a guided mindfulness meditation on the primary measures of executive function and critical thinking. The secondary measures assessed key thinking dispositions, including the need for cognition and actively open-minded thinking, state mindfulness and dispositional mindfulness. The 2 × 2 mixed analyses of variance showed no evidence of an effect of the interaction between time (pre vs. post) and group (mindfulness vs. sham meditation) on executive function indices (p < 0.39) or critical thinking performance (p = 0.11). No evidence was found for indirect effects of group allocation on critical thinking through either state mindfulness or executive function. Moderation models demonstrated evidence that the effects of the mindfulness meditation on critical thinking were conditional on need for cognition (b = −0.24 [−0.40, −0.08]) and actively open-minded thinking (b = −0.14 [−0.25, −0.04]) dispositions. In addition, participants who reported low levels of non-reactivity demonstrated decreased critical thinking performance following the mindfulness meditation, which was mediated by slower Electronic supplementary material The online version of this article (https://dx.doi.org/10.1007/s12671-017-0789-8) contains supplementary material, which is available to authorized users. * Chris Noone [email protected]

1

School of Psychology, National University of Ireland, Galway, Ireland

reaction times on the executive functioning task (b = −53.37 [−92.65, −14.08]). In summary, a brief guided mindfulness meditation appears to facilitate critical thinking for those low in need for cognition and actively open-minded thinking. However, it is unclear whether executive function is a mechanism underlying this relationship. Keywords Critical thinking . Executive function . Self-regulation . Dual-process theory . Thinking dispositions

Introduction In recent years, many researchers, practitioners, commercial and non-profit organisations and governments have made claims regarding the application of mindfulness practice to the improvement of everyday thinking skills (Mindfulness All-Party Parliamentary Group 2015; Good et al. 2016; Insead Knowledge 2014; Pykett et al. 2016). Closer examination of these references shows that many of these claims have been made in blogs and policy documents rather than peerreviewed source and with little reference to direct empirical evidence. Such research is much needed as, from an empirical point of view, it is an open question as to whether mindfulness helps, hinders or has little effect on everyday thinking skills, and therefore, these claims, and applications based on them, may be premature. When considering the theoretical foundation of a relationship between mindfulness and thinking, there are generally two main perspectives put forward. One view suggests that mindfulness is either not related to skill in everyday thinking, or even a hindrance to it, due to the importance of developing skill in acceptance and non-elaborative, or non-reactive, processing in learning mindfulness (Brendel 2015). Another view suggests that since mindfulness practice appears to result in

Mindfulness

improved executive control, it may facilitate the operation of reflective processes which are crucial to effective thinking (Shapiro et al. 2011). However, no consistent link between mindfulness and thinking skill has been established in the literature. Any such relationship may depend on a range of factors including whether dispositional mindfulness or state mindfulness is the focus of the study, the research design being employed, the context in which the study takes place, the specific thinking skill being assessed and individual differences amongst study participants. Inter- and intra-individual differences in everyday thinking skill are best measured using assessments developed in the field of research focused on critical thinking. Cognitive psychologists operationalise critical thinking as the effective use of the cognitive skills of analysis, evaluation and inference, in a purposeful, reasoned and goal-directed manner (Halpern 1998). The appropriate execution of these critical thinking skills depends on the presence of specific dispositions towards thinking (Ku 2009). It also depends on the thinker’s awareness that a specific thinking skill is required, that the ongoing execution of the skill is adequate and the ability to exert control to change ongoing thinking processes if necessary (Halpern 1998). These measures are most appropriate as indicators of everyday thinking skills because of their ecological validity (Butler 2012) and their sensitivity to both the cognitive and dispositional aspects of critical thinking (Ku 2009). Just one study has focused specifically on examining the effects of mindfulness on critical thinking (Noone et al. 2015), but there have been others which have focused on related cognitive outcomes such as cognitive rigidity (Greenberg et al. 2012), insight problem-solving (Ostafin and Kassman 2012) and creative thinking (Colzato et al. 2017). These studies all highlighted, but did not experimentally investigate, the inhibition of automatic thinking processes as a possible executive control or self-regulation mechanism underlying the positive effects of mindfulness on thinking skills. Whilst these studies together do appear to support the view of mindfulness as facilitative of the self-regulation of thinking, it should be noted that the relationship is most likely not so straightforward. For instance, the previously mentioned study by Noone et al. (2015) showed that in addition to positive indirect effects of both components of mindfulness, there was a negative direct effect of non-reactivity on critical thinking. This suggests that there is some merit to the idea that the aspects of mindfulness which are associated with acceptance may in fact hinder critical thinking. However, this study was crosssectional in nature so experimental studies are needed to confirm the relationships observed in it. Both components of mindfulness may contribute to the inhibition of automatic processes in different ways. Presentmoment focused attention, sometimes referred to simply as observing, involves the awareness of all internal and external stimuli at any moment in time (Anicha et al. 2012). This

facilitates the engagement of executive control because it allows subtle affective cues which are normally overlooked to be noticed. These affective cues trigger executive control by indicating that the current state the individual is experiencing is inconsistent with their goal state (Teper et al. 2013). Normally, when such affective cues are noticed, this can trigger elaborative processes which lead to the development of longer-lasting emotions and moods and can take up working memory resources (Spies et al. 1996). In cultivating a mindful state, individuals must process these cues in a non-reactive manner. This requires the inhibition of elaboration and/or suppression of affective cues before intense emotional reactivity to the attended thoughts, feelings and sensations can occur (Teper et al. 2013). Therefore, the mobilisation of executive control is central to the cultivation of a state of mindfulness. Executive control is also vital to effective critical thinking (Facione 2013). One of the most influential set of theories explaining the importance of executive control to critical thinking is that of dual-process theories. These theories posit that two separate cognitive systems are available to us when processing information (Evans and Stanovich 2013). Type 1 processes are fast, occur in parallel and do not exert any demand on working memory resources as they are relatively automatic. Type 2 processes are slow, occur serially and require working memory resources. The three-stage model of analytic engagement is perhaps the most well-refined dualprocess theory of higher-order cognition as it specifies the mechanisms by which this self-regulation occurs and the conditions under which it will lead to an optimal outcome (Pennycook et al. 2015). It states that type 1 processes are always triggered by default when information is being processed and these result in an intuitive response. It is only through the intervention of executive functions that type 2 processes, such as critical thinking, are activated, through which alternative responses are generated and considered (Bonnefon 2016). This is where executive control is key as it is only when conflict, due to an inconsistency between the available responses, is detected that control is exerted through the executive functions to reduce this inconsistency (Hofmann et al. 2012). One source of information regarding such inconsistencies is our affective cues, which we are better able to notice and act on, without interruption by emotional reactivity, when in a mindful state (Teper et al. 2013). It is important to note, however, that engagement in a state of mindfulness cannot be assumed to affect different individuals to the same degree. Therefore, it is important to include, where possible, baseline measures of task performance in the experimental designs employed and to take relevant traits or dispositions into account. In this study, dispositional mindfulness, actively open-minded thinking and need for cognition were the dispositions of interest. Dispositional mindfulness was measured because there is evidence to suggest that a greater general tendency to engage in a mindful state boosts

Mindfulness

the effect of brief mindfulness inductions—even in novice mindfulness practitioners (e.g. Dickenson et al. 2013; Kee et al. 2012). Need for cognition reflects an individual disposition to enjoy engaging in effortful cognitive activity: it is strongly associated with critical thinking and, to a much lesser extent, significantly related to mindfulness (Brown and Ryan 2003). Previous discussion of mindfulness interventions suggested that those with a higher need for cognition would be more likely to engage with mindfulness as it is a cognitively demanding activity, and for this reason, we expected that the effectiveness of the mindfulness induction would be moderated by levels of need for cognition (Chatzisarantis and Hagger 2007). Actively open-minded thinking refers to the tendency to process information in a flexible manner and remain open to revising one’s beliefs (Stanovich and West 1997). This disposition is highly predictive of effective critical thinking and has been associated with openness to experience (Oyer et al. 2012). It was predicted that this would also moderate the effectiveness of the mindfulness induction such that more openminded individuals would engage with the meditation to a greater extent. In summary, this study was designed to test the effects of a brief mindfulness meditation on executive function and critical thinking against those of a sham meditation. In addition, mediation analyses were planned to assess whether engaging in a brief mindfulness meditation increased critical thinking performance indirectly through its effect on executive function. Finally, moderation analyses were planned to investigate whether the direct and indirect effects mentioned above are conditional on individual differences in dispositions towards mindfulness, need for cognition and actively open-minded thinking. The specific hypotheses are outlined in Table 1.

Method Participants A total of 65 completed participation in this study, whilst one participant withdrew during the procedure. Of these, 73.8% were female (N = 48). The majority of the participants were Irish (89.3%) and all were students of the National University of Ireland, Galway, in either the first or second year of their undergraduate studies (mean age = 21.09, SD = 5.46). First year and second year psychology students were awarded course credit for participating. Of the participants, 95.4% reported no experience with meditation. The remaining 4.6% had not experienced formal training or practiced regularly but had attended once-off events related to meditation. Therefore, no analyses regarding previous experience with mindfulness were conducted. The statistical program G*Power was used to conduct power analysis a priori. With two groups, two measurements, an assumed correlation

amongst repeated measures of 0.3 (typically low in such research; Rossi 2012) as well as a medium effect size (r = 0.3, again typical in research on the cognitive effects of mindfulness; Chiesa et al. 2011), the recommended sample size to achieve 80% power for the 2 × 2 mixed analyses of variance (ANOVAs) was 60. Procedure All study participants attended the School of Psychology labs at NUI Galway for a single 2-h study session. Participants first completed informed consent and a demographic sheet. They then completed measures of the need for cognition and actively open-minded thinking, state mindfulness and dispositional mindfulness. Next, the behavioural tasks were counterbalanced so that participants then either completed the executive function task or the critical thinking task. After these tasks, the participants either listened to the guided mindfulness meditation or a guided sham meditation. Participants then indicated the extent to which they understood the induction instructions and the extent to which they attempted to follow them. Then, participants completed the state mindfulness measure again as a manipulation check. Again, the tasks were counterbalanced so participants either completed the executive function task or the critical thinking task. Following each task, participants indicated the extent to which they applied the quality of attention cultivated during the induction of the task. Finally, participants were debriefed. Experimental Manipulation It was decided to employ the guided meditation scripts kindly provided by Arch and Craske (2006) due to their extensive previous use. The mindfulness meditation condition required participants to listen to a guided meditation for 10 min. The mind-wandering control condition used by Arch and Craske (2006) was presented as if it was a guided meditation (and is therefore referred to as the sham meditation condition). This acted as an active control and was intended to simulate an everyday thinking state as we tend to mind-wander for up to 30% of our waking hours (Kane et al. 2007). It therefore has high ecological validity and is a closer match than other active-control methods (e.g. reading, listening to educational material). Measures N-Back The N-back task is a commonly used measure of executive function and working memory (Baddeley 2003). In this version of the task, participants viewed letters successively presented on a screen. In the 2-back condition, participants

Mindfulness Table 1

Hypotheses

Hypothesis

Variables

Test

1.1 Greater increase in executive control for experimental group

DVs = (a) 2-back D′ (b) 2-back accuracy (c) 2-back RT; IVs = time, group

2×2 mixed ANOVAs

1.2 Greater increase in critical thinking for experimental group 1.3 Executive control mediates effect of experimental manipulation on critical thinking

DVs = shortened Halpern critical thinking assessment; IVs = time, group DV = time 2 shortened Halpern critical thinking; IV = group MV = (a) 2-back D′ (b) 2-back accuracy (c) 2-back RT at time 2 CV = time 1 shortened Halpern critical thinking

2 × 2 mixed ANOVA

Primary

PROCESS, model 4

Secondary 2.1 Increase in critical thinking for experimental group is conditional on level of need for cognition 2.2 Increase in critical thinking for experimental group is conditional on level of actively open-minded thinking 2.3 Greater increase in executive control for experimental group if they are high in observing and non-reactivity 2.4 Greater increase in critical thinking for experimental group if they are high in observing and non-reactivity 2.5 Executive control mediates effect of experimental manipulation on critical thinking in those with high dispositional mindfulness

DV = time 2 shortened Halpern critical thinking; IV = group ModV = need for cognition; CV = time 1 shortened Halpern critical thinking DV = time 2 shortened Halpern critical thinking; IV = group ModV = actively open-minded thinking; CV = time 1 shortened Halpern critical thinking DV = (a) 2-back D′ (b) 2-back accuracy (c) 2-back RT at time 2; ModVs = observing, non-reactivity sub-scales; CV = (a) 2-back D′ (b) 2-back accuracy (c) 2-back RT at time 1 DV = time 2 shortened Halpern critical thinking; IV = group ModVs = observing sub-scale, non-reactivity sub-scale; CV = time 1 shortened Halpern critical thinking DV = time 2 shortened Halpern critical thinking; IV = group MedV = (a) 2-back D′ (b) 2-back accuracy (c) 2-back RT at time 2 ModV = observing, non-reactivity sub-scales; CV = time 1 shortened Halpern critical thinking

PROCESS, model 1 PROCESS, model 1 PROCESS, model 2 PROCESS, model 2 PROCESS, model 10

See Appendix B (Supplementary Material) for the conceptual diagrams of the mediation and moderation model IV independent variable, DV dependent variable, CV covariate, ModV moderator variable, MedV mediator variable

responded to a letter as a target when it was identical to the letter presented two trials earlier. The letters were presented for 500 ms followed by a 2000-ms inter-stimulus interval during which the letter was replaced by a fixation cross. In all conditions, 33% of letters were targets. A number of indicators of performance have been used in studies involving the N-back including reaction time (RT), accuracy (i.e. correctly identified targets and correctly rejected non-targets) and D′. D′ is the difference between the Z transforms of the hit rate and the false alarm rate. As there is no preferred dependent variable (DV) used in studies employing the N-back, and in the interest of transparency, results for each indicator of performance are reported and a Bonferroni correction is applied (p = 0.17).

experimental manipulation as using the same items before and after would see the participants’ memory confound their critical thinking performance. These shortened versions of the HCTA were validated using an item parcelling strategy. A total of 20 points were available in each version, and these points were awarded to answers based on a standardised promptbased scoring system. The DV employed was the total score for each participant at each time. Scale reliability was assessed using the scale diagnosis function from the UserFriendlyScience package in R (Peters 2014). This showed moderately adequate reliability across the items (Cronbach’s α = 0.45, ω = 0.64, greatest lower bound = 0.72). Five Facet Mindfulness Questionnaire–Short Form (Bohlmeijer et al. 2011)

Halpern Critical Thinking Assessment (Halpern 2010) The Halpern Critical Thinking Assessment (HCTA) assesses thinking in everyday, easy to relate to scenarios and is sensitive to both the motivational and behavioural aspects of critical thinking (Ku 2009). The Halpern Critical Thinking Assessment was adapted to produce two short forms to measure critical thinking performance before and after the

The Five Facet Mindfulness Questionnaire–short form (FFMQ-SF) is a 24-item measure consisting of five subscales which assesses the observing, describing, acting with awareness, non-judging and non-reactivity facets of dispositional mindfulness. The FFQM-SF employs a five-point Likert scale (e.g. 1 = never or very rarely true, 5 = very often or always true). For the purposes of the current study, the DVs employed

Mindfulness

were the total scores for the observing and non-reactivity subscales. This scale includes four observing items and five nonreactivity items. Moderate reliability for the observing subscale (Cronbach’s α = 0.53, ω = 0.80, greatest lower bound = 0.65) and adequate reliability for the non-reactivity subscale (Cronbach’s α = 0.75, ω = 0.82, greatest lower bound = 0.83) were found.

and the extent to which they followed them on a seven-point Likert scale. After each of the post-manipulation tasks, participants were asked to rate their own application of the instructions to their attention during the tasks on a seven-point Likert scale. See Appendix A (Supplementary Material) for the manipulation check results. Data Analyses

Need for Cognition–Short Form (Cacioppo et al. 1984) The Need for Cognition–short form is an 18-item measure which measures the extent to which individuals tend to engage in effortful cognitive activity (Cacciopo et al. 1984). The scale includes 18 items which are rated on a five-point Likert scale (e.g. 1 = extremely uncharacteristic of me, 5 = extremely characteristic of me). It has been extensively validated as unifactorial and has been found to have adequate reliability (Tolentino et al. 1990). The total score for each participant was used as the DV. This scale showed excellent reliability in this study (Cronbach’s α = 0.87, ω = 0.90, greatest lower bound = 0.96). Actively Open-Minded Thinking Scale (Stanovich and West 1997) The Actively Open-minded Thinking Scale assesses the extent to which individuals tend to approach information in an open and flexible way. The scale includes 41 items and these are rated on a six-point Likert scale (e.g. 1 = strongly agree, 6 = strongly disagree). Again, the total score for each participant was used as the DV. Scale diagnosis demonstrated good reliability (Cronbach’s α = 0.80, ω = 0.86, greatest lower bound = 0.85).

A number of analyses were carried out to ascertain the effects of the experimental manipulation of state mindfulness, evaluate whether greater executive control mediated any effects and identify the conditions, in terms of levels of mindfulness and thinking dispositions, under which these effects occur. These analyses and their associated hypotheses are summarised in Table 1. These analyses were completed using SPSS 22 (IBM Inc. 2013), the PROCESS macro (Hayes 2013) and JASP (JASP Team 2016).

Results Means, standard deviations and values for skewness and kurtosis are presented in Table 2. On visual inspection of Q-Q plots and histograms, each variable was found to be approximately normally distributed. Most variables were found to have acceptable levels of skewness and kurtosis. There was no missing data. Two extreme scores were identified in postexperimental manipulation N-back RT but re-analysis with winsorised scores produced very similar results so the original analyses were retained. No problematic outliers were found in other variables on inspection of box plots and z scores. Bivariate correlations between all measures are presented in Table 3.

Manipulation Checks Direct and Indirect Effects of Mindfulness Meditation Mindful Attention and Awareness Scale–State Version (Brown and Ryan 2003) The Mindful Attention and Awareness Scale–State version assesses participants’ level of mindfulness during a particular moment in time. The scale includes five items which are rated on a seven-point Likert scale (e.g. 0 = not at all, 6 = very much). The DV was the average score across the five items and adequate reliability was found for item scores before (Cronbach’s α = 0.46, ω = 0.83, greatest lower bound = 0.73) and after the experimental manipulation (Cronbach’s α = 0.58, ω = 0.79, greatest lower bound = 0.72). Understanding, Adherence to and Application of Instructions Following the experimental manipulation, participants were asked to rate their understanding of the guided instructions

Hypothesis 1.1 stated that there would be a greater increase in performance of the executive functioning task from before the guided meditations to after for those who received the mindfulness instructions rather than the sham instructions. This was tested using a series of 2 × 2 mixed ANOVA tests to examine whether a significant time by group interaction was present for three indicators of performance in the N-back— RT, accuracy and D′. The use of three outcomes for N-back performance was controlled for using a Bonferroni correction which adjusts the significance criterion to 0.017. Whilst there was a main effect of time for RT (F(1, 63) = 26.61, p < 0.001, ηp2 = 0.30), such that RT was faster for both groups after the experimental manipulation (M = 615 ms) than before (M = 693 ms), no significant main effect for group was found (F(1, 63) = 0.19, p = 0.67, ηp2 = 0.003), and crucially, the interaction effect was not significant either (F(1, 63) = 0.75,

Mindfulness Table 2

Descriptive statistics

Variable

Mindfulness meditation M

Observing Non-reactivity

SD

13.59 14.91

Need for cognition Actively open-minded thinking State mindfulness—time 1 State mindfulness—time 2 2-back D′—time 1 2-back D′—time 2 2-back accuracy—time 1 2-back accuracy—time 2 2-back reaction time—time 1 2-back reaction time—time 2 Critical thinking—time 1 Critical thinking—time 2

Sham meditation Skewness

2.52 2.64

0.28 0.07

M

−0.38 0.39

SD

14.10 14.23

Skewness

Kurtosis

2.70 3.69

−0.83 −0.09

0.44 −1.47

59.76

9.17

−0.19

0.38

58.55

11.48

−0.29

−1.13

149.32 4.76

15.97 0.84

0.22 0.05

−0.36 −0.69

155.81 5.01

14.43 0.92

0.09 −0.15

−1.00 −0.80

4.41 1.59

0.83 0.80

0.59 0.14

0.69 −0.93

4.48 1.47

0.88 0.88

0.21 0.18

−0.06 −1.27

1.55

0.92

−0.07

−1.15

1.67

0.90

0.17

−1.61

27.15 27.41

1.94 2.26

−0.70 −1.07

0.36 1.06

27.35 27.90

2.18 1.47

−0.69 −0.30

−0.08 −0.67

686.41 596.20

163.29 168.17

0.82 0.74

0.52 −0.35

698.92 634.60

307.29 310.95

2.37 2.46

5.57 6.82

7.50 8.71

3.64 2.98

0.42 −0.14

−0.75 −0.58

8.16 7.77

2.27 4.06

−0.07 0.37

−0.48

p = 0.39, ηp2 = 0.01). The accuracy of performance did not significantly differ according to either group (F(1, 63) = 0.72, p = 0.40, ηp2 = 0.01) or time (F(1, 63) = 2.21, p = 0.14, ηp2 = 0.03), and again, no significant interaction was observed (F(1, 63) = 0.27, p = 0.61, ηp2 = 0.004). Finally, there were no significant difference across time (F(1, 63) = 0.25, p = 0.62, ηp2 = 0.004) or group (F(1, 63) = 0.001, p = 0.98, ηp2 = 0.01) for D′ scores and the interaction effect was not statistically different from zero (F(1, 63) = 0.72, p = 0.40, ηp2 = 0.01). Hypothesis 1.2 stated that there would be a greater increase in performance of the critical thinking task for the Table 3

Kurtosis

−0.93

experimental group following the experimental manipulation in comparison to the control group. A 2 × 2 mixed ANOVA showed no differences across time (F(1, 63) = 0.70, p = 0.41, ηp2 = 0.01) or group (F(1, 63) = 0.04, p = 0.84, ηp2 = 0.001) and revealed a non-significant interaction between these (F(1, 63) = 2.63, p = 0.11, ηp2 = 0.04). Hypothesis 1.3 stated that executive function, indicated by performance on the N-back task, would mediate the effect of the experimental manipulation on critical thinking. A simple mediation model (model 4) was run using the PROCESS macro for SPSS with critical thinking performance before

Bivariate correlations between the primary and secondary measures 1 2

1. Observing 2. Non-reactivity 3. Need for cognition 4. Actively open-minded thinking 5. State mindfulness—pre

3

4

5

6

– 0.06 0.25* −0.01 −0.13 0.02 – −0.03 0.03 −0.10 −0.22 – 0.28* 0.22 0.20 – 0.18 0.18

6. State mindfulness—post 7. 2-back D—pre 8. 2-back D′—post 9. 2-back accuracy—pre 10. 2-back accuracy—post 11. 2-back RT—pre 12. 2-back RT—post 13. Critical thinking—pre 14. Critical thinking—post *p < 0.05, **p < 0.01, ***p < 0.001

–

7

8

−0.02 0.19 −0.16 0.03

−0.08 −0.05 −0.07 −0.12 −0.16 0.02 −0.12 −0.06

0.49*** −0.06 −0.13 –

9

10

11

12

0.002 −0.08 −0.09 −0.14 0.23 0.16 0.05 −0.18 −0.26* 0.32** −0.09 −0.01

0.003 −0.08

−0.09 −0.10

−0.03 0.03 0.10 −0.08 −0.11 −0.19 – −0.13 −0.08 −0.09 −0.10 −0.003 – 0.27* 0.19 0.19 0.07 – 0.39** 0.15 0.06 – 0.17 0.32** – 0.88*** –

13

14

−0.04 −0.06 0.15 0.09 0.14 0.12 0.39** 0.37** 0.18

0.18

0.18 0.07 0.05 0.21 0.10 0.08 0.13 –

0.20 −0.01 −0.09 −0.02 −0.02 −0.25* −0.23 0.27* –

Mindfulness

the experimental manipulation entered as a covariate. This was run for all three indicators of N-back performance. No significant direct or indirect effects were found for either RT (direct effect = 1.03, 95% CI −0.62 to 2.69; indirect effect = 0.12, 95% CI −0.27 to 0.68), accuracy (direct effect = 1.19, 95% CI −0.56 to 2.94; indirect effect = −0.04, 95% CI −0.44 to 0.32) or D′ (direct effect = 1.14, 95% CI −0.58 to 2.86; indirect effect = 0.01, 95% CI −0.16 to 0.50). Confidence intervals were bias-corrected. Conditional Effects of Mindfulness Meditation Hypothesis 2.1 stated that improvement in critical thinking performance would depend on levels of need for cognition. This was tested using a simple moderation model specified with the PROCESS macro (model 1). In this model, group assignment (coded as 0 for sham meditation and 1 for mindfulness meditation), need for cognition, their interaction (to test for moderation) and baseline critical thinking performance (to control for individual differences) were entered as predictors of post-manipulation critical thinking performance. The model accounted for 22% of the variance in post-manipulation critical thinking performance (F(4, 60) = 4.16, p = 0.005). As can be seen in Table 4, each of these predictors had a significant effect on post-manipulation critical thinking performance. Since the interaction between group assignment and need for cognition was significant, this moderation effect was probed using the Johnson-Neyman technique to identify regions of significance (as shown in Fig. 1a; Hayes 2013). This revealed that there was a significant positive effect for those in the mindfulness meditation group with need for cognition scores below 57, which was increasingly strong for lower scores. This applied to 40% of the sample. Overall, the inclusion of this moderation effect in the model led to a R2 change of 11% (F(1,60) = 8.61, p = 0.005). Whilst there was also a significant negative effect for those in the mindfulness

meditation group with need for cognition scores above 79, this was disregarded because it did not make substantive sense as it only applied to 1.5% of cases. Hypothesis 2.2 stated that improvement in critical thinking performance would be conditional on levels of actively openminded thinking. Again, this was tested by running a simple moderation model with the PROCESS macro (model 1). In this model, group assignment, actively open-minded thinking, their interaction and baseline critical thinking performance were entered as predictors of post-manipulation critical thinking performance. This model accounted for 29% of the variance in post-manipulation critical thinking performance (F(4, 60) = 6.09, p = 0.0003). As can be seen in Table 4, each of these predictors had a significant effect on post-manipulation critical thinking performance except baseline critical thinking. Since the interaction between group assignment and actively open-minded thinking was significant, this moderation effect was probed using the Johnson-Neyman technique. Again, this allows the identification of regions of significance and how the size of the effect of the experimental manipulation differs according to levels of actively open-minded thinking (as shown in Fig. 1b). This revealed that there was a significant positive effect for those in the mindfulness meditation group with actively open-minded thinking scores below 182—which applies to 51% of cases—which was increasingly strong for lower scores. Overall, the inclusion of this moderation effect in the model led to a R2 change of 9% (F(1,60) = 7.22, p = 0.009). Hypothesis 2.3 stated that the direct effect of the mindfulness manipulation on executive function would depend on dispositional levels of mindfulness. This was tested by using the PROCESS macro to run a model in which this direct effect was moderated by the observing and non-reactivity sub-scales of the FFMQ-SF separately (model 2). In this model, group assignment, observing and non-reactivity sub-scales, their interactions with group assignment and baseline N-back performance were entered as predictors of post-manipulation N-

Table 4 Models of moderation of experimental effect by need for cognition and actively openminded thinking

95% CI

Hypothesis 2.1 Group Need for cognition Group × need for cognition Critical thinking—time 1 Hypothesis 2.2 Group Actively open-minded thinking Group × actively open-minded thinking Critical thinking—time 1

b

SE

t

p

LL

UL

15.35 0.12 −0.24 0.40

4.92 0.05 0.08 0.14

3.12 2.29 −2.94 2.92

0.002 0.03 0.005 0.005

5.52 0.01 −0.40 0.13

25.19 0.22 −0.08 0.67

27.10 0.16 −0.14 0.25

9.53 0.04 0.05 0.14

2.84 3.98 −2.69 1.78

0.006 0.0002 0.009 0.08

8.03 0.08 −0.25 −0.03

46.16 0.24 −0.04 0.52

Mindfulness

Fig. 1 Moderation of effect of mindfulness meditation (MM) by a need for cognition and b actively open-minded thinking. Horizontal line at 0 indicates no effect. A significant effect is present when this line does not fall between the 95% CI lines

back performance (in terms of RT, accuracy and D′). Neither the interaction of group and level of observing (RT b = 0.003, 95% CI −0.02 to 0.01; accuracy b = −0.23, 95% CI −0.60 to 0.13; D′ b = 0.06, 95% CI −0.13 to 0.24) nor the interaction between group and level of non-reactivity (RT b = 0.002, 95% CI −0.01 to 0.02; accuracy b = −0.12, 95% CI −0.42 to 0.18; D′ b = −0.01, 95% CI −0.16 to 0.15) were significant for any indicator of N-back performance. Hypothesis 2.4 stated that the direct effect of the mindfulness manipulation on critical thinking would depend on dispositional levels of mindfulness. Again, the PROCESS macro was used to run a model in which this direct effect was moderated by the observing and non-reactivity subscales of the FFMQ-SF separately (model 2). In this model, group assignment, observing and non-reactivity sub-scales, their interactions with group assignment and baseline critical thinking performance were entered as predictors of post-manipulation critical thinking performance. Group assignment did not significantly interact with either observing (b = −0.47, 95% CI −0.99 to 0.34) or non-reactivity (b = 0.29, 95% CI −0.29 to 0.87). Hypothesis 2.5 stated that the indirect effect of the mindfulness manipulation on critical thinking through N-back performance would depend on dispositional levels of mindfulness. This was tested by specifying a moderated mediation model in PROCESS (model 10). This model included group assignment, post-manipulation N-back performance, observing and non-reactivity sub-scales, their interactions with group assignment and post-manipulation N-back performance and baseline critical thinking performance. No interaction effects or conditional indirect effects were found in the models which included accuracy or D′ as indicators of N-back performance. However, the model which employed RT as an indicator of Nback performance showed evidence for an interaction between

non-reactivity and group assignment. This interaction was probed further by examining the bootstrapped confidence intervals (95%, bias-corrected) of the conditional indirect effect of group assignment on critical thinking through N-back performance at the 10th, 25th, 50th, 75th and 90th percentiles of the distributions of non-reactivity and observing. This revealed that when non-reactivity is very low or low (i.e. there is a tendency to be reactive) and observing is either moderate, high or very high (which pertains to 18.46% of the sample), there was a significant, negative conditional indirect effect. The nature of these effects, which were small in size, was such that assignment to the mindfulness meditation group led to poorer N-back performance in comparison to the control group which accounted for similarly impaired postmanipulation critical thinking task performance (see Fig. 2).

Discussion The aim of this study was to experimentally examine the effects of a brief mindfulness meditation on executive function and critical thinking and to investigate the extent to which these would interact with dispositions towards thinking and engaging in mindfulness. The results of this study suggest that, for naïve meditators at least, the effects of mindfulness meditation on executive function and critical thinking are complex. Whilst no simple direct or indirect effects were found, significant and substantive controlled direct effects, conditional direct effects and conditional indirect effects were found which have interesting implications for theories and applications of mindfulness. The first primary hypothesis stated that performance on the executive function task would improve more, from before the experimental manipulation to after it, for those in the

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Fig. 2 Size of conditional indirect effect of assignment to mindfulness meditation (MM) group on critical thinking through N-back performance as a function of observing at very low (a) and low (b) levels of non-

reactivity. Horizontal line at 0 indicates no effect. A significant effect is present when this line does not fall between the 95% CI lines

mindfulness meditation (MM) group compared to those in sham meditation (SM) group. Since the interaction between time and group assignment was not significant for any indicator of executive function performance, this hypothesis was rejected. There was evidence for a ceiling effect on the executive function task, in terms of accuracy, as participants in both groups only made, on average, two mistakes in each block. Therefore, the task may not have been difficult enough to elicit individual differences in executive function. There was a much greater range of RTs which may be indicative of individual differences in executive function, or the speed with which executive operations are executed. Overall, it is inconclusive as to whether the experimental manipulation failed to affect executive function or the task failed to accurately reflect executive function. A review of past literature on the effects of mindfulness on N-back performance reveals positive effects in individual differences and intervention designs (Ruocco and Direkoglu 2013; Zeidan et al. 2010). However, a more recent study with a similar design showed that performance on a Nback task was not sensitive to a single brief mindfulness meditation (Johnson et al. 2015), and the results here appear to replicate this finding. The second primary hypothesis focused on whether performance on the critical thinking task would improve, from before the experimental manipulation to after it, to a greater extent for those in the MM group compared to those in the SM group. This hypothesis was not supported as the interaction between time and group assignment was not significant. This would seem to indicate that engaging in a brief mindfulness meditation is no better on average than a sham meditation at improving critical thinking performance. However, differential effects of mindfulness meditation on critical thinking may exist as discussed below.

The third primary hypothesis concerned testing whether mediation was present in the relationship between mindfulness, executive function and critical thinking. Results provided no evidence for executive function mediating the relationship between mindfulness and critical thinking, contrary to previous cross-sectional findings (Noone et al. 2015). This may have been due to the task not being difficult enough as discussed above. Another possibility is that though the task employed, the N-back, is a recognised measure of executive function, it may not rely heavily enough on the process of inhibition to have benefited from the mindfulness meditation. The first secondary hypothesis stated that the effect of the mindfulness meditation on critical thinking performance would be conditional on individual levels of need for cognition. In the current study, the mindfulness meditation involved a much greater cognitive demand than the sham meditation so it was expected that those with a greater need for cognition would benefit more from engaging in it. Results revealed an effect in the opposite direction. The beneficial effect of the mindfulness meditation on critical thinking was greater for those lower in need for cognition. Individuals high in need for cognition did not benefit from the mindfulness meditation, possibly because their level of cognitive engagement during both testing occasions was already high and was the strongest determinant of their performance. This suggests that a brief mindfulness meditation may help overcome a tendency to put little effort into critical thinking. This parallels previous research on the potential of mindfulness to decrease engagement in maladaptive habits of thinking (Vago 2014). This has been demonstrated empirically in studies focusing on the effects of mindfulness on habitual worry and cognitive rigidity (Greenberg et al. 2012; Verplanken and Fisher 2014).

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The next secondary hypothesis concerned whether the effect of the mindfulness meditation on critical thinking performance would also depend on individual levels of actively open-minded thinking. It was thought the extent to which an individual had an open-minded disposition would positively influence their willingness to process the instructions given during the guided meditation in a flexible manner. The results demonstrated a similar pattern to those found in the previous analysis. The mindfulness mediation was only beneficial for critical thinking to those lower in actively open-minded thinking, and this effect became stronger as levels of actively open-minded thinking decreased. Therefore, for those less inclined to approach information in a flexible manner, engaging in the mindfulness meditation enhanced critical thinking performance, whereas those already inclined to process information in a flexible manner did not experience any extra benefit due to the mindfulness meditation. As can be seen in Table 4, actively open-minded thinking was correlated with baseline critical thinking, and therefore, those lower in this thinking disposition had more room to improve in their critical thinking performance. People who are low in actively open-minded thinking tend to rely overly on their biases (Price et al. 2015). The moderation effect found here connects to research on how engaging in mindfulness practice can reduce biased thinking as has been demonstrated in studies on the sunk cost bias (Hafenbrack et al. 2014), the correspondence bias (Hopthrow et al. 2016) and the covariation bias (Goodman 2014). Furthermore, a single brief mindfulness meditation has been shown to reduce an objective behavioural indicator of closed-mindedness—specifically, in a task involving a game of trust with partners of different races, where the mindfulness group demonstrated significantly less bias towards their own race than the control groups (Lueke and Gibson 2016). The third secondary hypothesis examined whether the direct effect of the experimental manipulation on executive function depended on dispositional tendencies to engage in present-moment attention and non-reactivity. This was investigated as previous studies had demonstrated that the effects of mindfulness inductions can be conditional on dispositional levels of mindfulness (Dickenson et al. 2013; Kee et al. 2012) and observing and non-reactivity have been shown to be associated with aspects of executive function (Anicha et al. 2012; Noone et al. 2015). No evidence for a conditional direct effect was found in the current study. The fourth secondary hypothesis stated that the direct effect of the experimental manipulation on critical thinking would depend on individual dispositions towards observing and non-reactivity. Again, it was expected that those higher in these mindfulness dispositions would benefit to a greater extent than others from the mindfulness meditation. Results provided no evidence to suggest that either observing or

non-reactivity moderated the effect of the mindfulness meditation on critical thinking, even when thinking dispositions were controlled for. Further research is needed to clarify the relationship between dispositional mindfulness, state mindfulness and critical thinking. The final secondary hypothesis focused on the presence of a conditional indirect effect dependent on dispositional mindfulness in the relationship between mindfulness meditation, executive function and critical thinking. It was expected that for those with higher levels of observing and non-reactivity, engaging in the mindfulness meditation would enhance their critical performance and that this could be accounted for by improvements in the executive function task. Whilst this exact relationship was not found, there was a finding which corresponds to it. Specifically, it was found that, for low levels of non-reactivity, engaging in the mindfulness meditation had a significant negative effect and that this was accounted for by an increase in RT on the executive function task. This was true for participants who exhibited at least a moderate level of observing but no such effect was seen for lower levels of observing. This tendency towards present-moment observation coupled with a reactive disposition is characteristic of anxious individuals (Anicha et al. 2012). Therefore, it is possible that the mindfulness meditation elicited anxiety in these participants which impaired their executive functioning, and ultimately their critical thinking also. This finding is tentative as the effect was small and affected less than 20% of the sample. Still, these results are in line with previous findings suggesting that the two defining aspects of mindfulness, observing and nonreactivity, are skills which have distinct skill acquisition trajectories and that practicing observation of the presentmoment without a sufficient level of non-reactivity may be lead to negative outcomes (Eisenlohr-Moul et al. 2012; Neale-Lorello and Haaga 2015). Present-moment observation tends to develop more quickly than non-reactivity (Lilja et al. 2013). Furthermore, people vary in their baseline tendency to employ these skills effectively, as shown in this study, and this can lead to very different, and possibly detrimental, reactions to initial attempts at meditation. This was a carefully designed study which was intended to avoid specific methodological weaknesses present in previous studies involving brief mindfulness meditations. This was achieved through the management of demand characteristics and expectation effects (see ethical statement), effective randomisation, the inclusion of an active control condition and the a priori calculation of the sample size required. In addition, understanding of, adherence to and application of the experimental manipulation instructions did not appear to differ according to group assignment. This methodological rigour was coupled with a fine-grained statistical approach which took potential differential responses to the experimental manipulation into account.

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Limitations This study was not without weaknesses. One way of improving this study would be to employ a more difficult or complex executive control task or one which specifically targets inhibition, as this was previously shown to be the specific mediating aspect of executive control (Noone et al. 2015). Replication with a larger sample is warranted to test the reliability of these findings. Whilst our sample size provided adequate power for most of our analyses, some of the more complex secondary analyses involving mediation must be acknowledged as underpowered as our sample size only allowed us to detect medium to large effects with 80% power (Fritz and MacKinnon 2007). Another limit of this type of research more generally is that there is scant empirical information regarding the best way to manipulate and measure state mindfulness. For example, brief mindfulness meditations vary in their length, focus and method of delivery and there is little consistency in the control conditions to which they are compared. This is a serious limitation to mindfulness research. For example, a recent content analysis of mindfulness studies employing brief meditations highlighted several implicit features of how these meditations are guided which could affect subsequent behaviour including the amount of silence used, the level of agency given to the participants, whether eyes are open or closed, whether inner speech is suggested and whether there is a focus on a problem to be solved or not (Fisher et al. 2016). Systematic research which compares different methods of manipulating mindfulness is required. Researchers should also consider more objective methods of assessing mindfulness states such as the Mindfulness Breath Awareness Score task and the Breath Counting task (Frewen et al. 2016; Levinson et al. 2014). In summary, analysis of the effect of a brief mindfulness meditation on critical thinking (as compared to a sham meditation) revealed no direct or indirect effects (i.e. through executive function). However, conditional direct effects suggested that a brief mindfulness meditation may improve critical thinking performance for those with lower tendencies towards applying effort to thinking and thinking in a flexible, open manner. The effect of the mindfulness meditation also appeared to depend on dispositional levels of mindfulness, although this effect was small and should be interpreted with caution. Specifically, engaging in the mindfulness mediation appeared to diminish executive function and critical thinking performance for those with a tendency to process information in a reactive manner. These results show the need for a more rigorous and nuanced approach to the study of mindfulness and support a more contextual view of mindfulness.

Acknowledgements This research was made possible by the award of a Galway Doctoral Research Scholarship to the first author. The authors would like to thank Ms. Nicola Hohensee for her assistance during data collection and Mr. Declan Coogan and Mr. Joseph Mee for the technical assistance.

Author Contributions CN: designed and executed the study, completed the data analysis and wrote the paper. MH: advised on the design, execution and analysis of the study and collaborated in the writing and editing of the paper. Compliance with Ethical Standards Ethical Statement Ethical approval for this study was granted by the NUI Galway Research Ethics Committee. Whilst informed consent was sought before participation in the study began, this information was not complete in order to reduce demand characteristics and ensure that expectation effects were equal across groups. Rather, participants were informed that the study focused on the effects of relaxation on attention and critical thinking and both conditions presented as a break during the experimental procedure to relax with a guided meditation. This type of deception is typical in psychological research and is an important control in mindfulness research (e.g. Mrazek et al. 2012). The word Bmindfulness^ was not mentioned in any recruiting or experimental materials. There was a full debriefing regarding the purpose of the study and the purpose of the deception following each lab session.

References Anicha, C. L., Ode, S., Moeller, S. K., & Robinson, M. D. (2012). Toward a cognitive view of trait mindfulness: distinct cognitive skills predict its observing and nonreactivity facets. Journal of Personality, 80(2), 255–285. doi:10.1111/j.1467-6494.2011.00722.x. Arch, J. J., & Craske, M. G. (2006). Mechanisms of mindfulness: emotion regulation following a focused breathing induction. Behaviour Research and Therapy, 44(12), 1849–1858. doi:10.1016/j.brat. 2005.12.007. Baddeley, A. (2003). Working memory: looking back and looking forward. Nature Reviews Neuroscience, 4(10), 829–839. doi:10.1038/ nrn1201. Bohlmeijer, E., Klooster, P. M., Fledderus, M., Veehof, M., & Baer, R. (2011). Psychometric properties of the five facet mindfulness questionnaire in depressed adults and development of a short form. Assessment, 18(3), 308–320. doi:10.1177/1073191111408231. Bonnefon, J. F. (2016). The pros and cons of identifying critical thinking with system 2 processing. Topoi, 1–7. doi:10.1007/s11245-0169375-2 Brendel, D. (2015). There are risks to mindfulness at work. [Blog post]. Retrieved from https://hbr.org/2015/02/there-are-risks-tomindfulness-at-work/ Brown, K. W., & Ryan, R. M. (2003). The benefits of being present: mindfulness and its role in psychological well-being. Journal of Personality and Social Psychology, 84(4), 822–848. Butler, H. A. (2012). Halpern critical thinking assessment predicts realworld outcomes of critical thinking. Applied Cognitive Psychology, 26(5), 721–729. doi:10.1002/acp.2851. Cacioppo, J. T., Petty, R. E., & Kao, C. F. (1984). The efficient assessment of need for cognition. Journal of Personality Assessment, 48(3), 306–307. doi:10.1207/s15327752jpa4803_13. Chatzisarantis, N. L. D., & Hagger, M. S. (2007). Mindfulness and the intention-behavior relationship within the theory of planned behavior. Personality and Social Psychology Bulletin, 33(5), 663–676. doi:10.1177/0146167206297401. Chiesa, A., Calati, R., & Serretti, A. (2011). Does mindfulness training improve cognitive abilities? A systematic review of neuropsychological findings. Clinical Psychology Review, 31(3), 449–464. doi:10. 1016/j.cpr.2010.11.003. Colzato, L. S., Szapora, A., Lippelt, D., & Hommel, B. (2017). Prior meditation practice modulates performance and strategy use in

Mindfulness convergent- and divergent-thinking problems. Mindfulness, 8(1), 10–16. doi:10.1007/s12671-014-0352-9. Dickenson, J., Berkman, E. T., Arch, J., & Lieberman, M. D. (2013). Neural correlates of focused attention during a brief mindfulness induction. Social Cognitive and Affective Neuroscience, 8(1), 40– 47. doi:10.1093/scan/nss030. Eisenlohr-Moul, T. A., Walsh, E. C., Charnigo Jr., R. J., Lynam, D. R., & Baer, R. A. (2012). The Bwhat^ and the Bhow^ of dispositional mindfulness: using interactions among subscales of the five-facet mindfulness questionnaire to understand its relation to substance use. Assessment, 19(3), 276–286. doi:10.1177/1073191112446658. Evans, J. S. B. T., & Stanovich, K. E. (2013). Dual-process theories of higher cognition: advancing the debate. Perspectives on Psychological Science, 8(3), 223–241. doi:10.1177/1745691612460685. Facione, P. A. (2013). Critical thinking: what it is and why it counts (2013 Update). San Jose: California Academic Press. Fisher, N. R., Thompson, L., & Malinowski, P. (2016). What is being induced in mindfulness experiments? A systematic analysis of the components, composition and emphasis of Bmindfulness inductions^. Paper presented at the Internatioinal Conference on Mindfulness, Rome, Italy. Frewen, P., Hargraves, H., DePierro, J., Andrea, W. D., & Flodrowski, L. (2016). Meditation breath attention scores (MBAS): development and investigation of an internet-based assessment of focused attention during meditation practice. Psychological Assessment, 28(7), 830–840. doi:10.1037/pas0000283. Fritz, M. S., & MacKinnon, D. P. (2007). Required sample size to detect the mediated effect. Psychological Science, 18(3), 233–239. doi:10. 1111/j.1467-9280.2007.01882.x. Good, D., Lyddy, C., Glomb, T., & Bono, J. (2016). Mindfulness has big impacts for performance, decision making and career longevity. Retrieved from http://blogs.lse.ac.uk/businessreview/2016/03/02/ mindfulness-has-big-impacts-for-performance-decision-makingand-career-longevity/ Goodman, R. J. (2014). Present with an uncertain future: dispositional mindfulness, covariation bias, and event-related potential responses to emotional stimuli in uncertain contexts (Unpublished doctoral dissertation). Virginia Commonwealth University. Richmond, VA. Greenberg, J., Reiner, K., & Meiran, N. (2012). Mind the trap: mindfulness practice reduces cognitive rigidity. PLoS ONE, 7(5), e36206. doi:10.1371/journal.pone.0036206 Hafenbrack, A. C., Kinias, Z., & Barsade, S. G. (2014). Debiasing the mind through meditation: mindfulness and the sunk-cost bias. Psychological Science, 25(2), 369–376. doi:10.1177/ 0956797613503853. Halpern, D. F. (1998). Teaching critical thinking for transfer across domains: dispositions, skills, structure training, and metacognitive monitoring. American Psychologist, 53(4), 449–455. Halpern, D. F. (2010). Halpern critical thinking assessment. Moedling: SCHUHFRIED (Vienna Test System). Hayes, A. F. (2013). Introduction to mediation, moderation, and conditional process analysis: a regression-based approach. New York: Guilford Press. Hofmann, W., Schmeichel, B. J., & Baddeley, A. D. (2012). Executive functions and self-regulation. Trends in Cognitive Sciences, 16(3), 174–180. doi:10.1016/j.tics.2012.01.006. Hopthrow, T., Hooper, N., Mahmood, L., Meier, B. P., & Weger, U. (2016). Mindfulness reduces the correspondence bias. Quarterly Journal of Experimental Psychology, 70(3), 351–360. doi:10. 1080/17470218.2016.1149498. IBM Corp. (2013). IBM SPSS Statistics for Windows, version 22.0. Armonk: IBM Corp. Insead Knowledge. (2014) How mindfulness improves decision-making. Retrieved from http://www.forbes.com/sites/insead/2014/08/05/ how-mindfulness-improves-decision-making/ JASP Team. (2016). JASP, version 0.7.5.5. Amsterdam: JASP Team.

Johnson, S., Gur, R. M., David, Z., & Currier, E. (2015). One-session mindfulness meditation: a randomized controlled study of effects on cognition and mood. Mindfulness, 6(1), 88–98. doi:10.1007/ s12671-013-0234-6. Kane, M. J., Brown, L. H., McVay, J. C., Silvia, P. J., Myin-Germeys, I., & Kwapil, T. R. (2007). For whom the mind wanders, and when: an experience-sampling study of working memory and executive control in daily life. Psychological Science, 18(7), 614–621. doi:10. 1111/j.1467-9280.2007.01948.x. Kee, Y. H., Chatzisarantis, N. N. L. D., Kong, P. W., Chow, J. Y., & Chen, L. H. (2012). Mindfulness, movement control, and attentional focus strategies: effects of mindfulness on a postural balance task. Journal of Sport and Exercise Psychology, 34(5), 561–579. Ku, K. Y. L. (2009). Assessing students’ critical thinking performance: urging for measurements using multi-response format. Thinking Skills and Creativity, 4(1), 70–76. doi:10.1016/j.tsc.2009.02.001. Levinson, D. B., Stoll, E. L., Kindy, S. D., Merry, H. L., & Davidson, R. J. (2014). A mind you can count on: validating breath counting as a behavioral measure of mindfulness. Frontiers in Psychology, 5, 1202. doi:10.3389/fpsyg.2014.01202 Lilja, J. L., Lundh, L. G., Josefsson, T., & Falkenström, F. (2013). Observing as an essential facet of mindfulness: a comparison of FFMQ patterns in meditating and non-meditating individuals. Mindfulness, 4(3), 203–212. doi:10.1007/s12671-012-0111-8. Lueke, A., & Gibson, B. (2016). Brief mindfulness meditation reduces discrimination. Psychology of Consciousness: Theory, Research, and Practice, 3(1), 34–44. doi:10.1037/cns0000081. Mindfulness All-Party Parliamentary Group. (2015). Mindful nation UK. London: The Mindfulness Initiative. Neale-Lorello, D., & Haaga, D. A. F. (2015). The observing facet of mindfulness moderates stress/symptom relations only among meditators. Mindfulness, 6(6), 1286–1291. doi:10.1007/s12671-0150396-5. Noone, C., Bunting, B., & Hogan, M. J. (2015). Does mindfulness enhance critical thinking? Evidence for the mediating effects of executive functioning in the relationship between mindfulness and critical thinking. Frontiers in Psychology, 6, 2043. doi:10.3389/fpsyg. 2015.02043. Ostafin, B. D., & Kassman, K. T. (2012). Stepping out of history: mindfulness improves insight problem solving. Consciousness and Cognition, 21(2), 1031–1036. doi:10.1016/j.concog.2012.02.014. Oyer, B., Gillespie, M., Issah, M., & Fasko, D. (2012). The role of personality in argument evaluation. Inquiry: Critical Thinking Across the Disciplines, 27(2), 40–49. Pennycook, G., Fugelsang, J. A., & Koehler, D. J. (2015). What makes us think? A three-stage dual-process model of analytic engagement. Cognitive Psychology, 80, 34–72. doi:10.1016/j.cogpsych.2015.05. 001. Peters, G.-J. Y. (2014). The alpha and the omega of scale reliability and validity: why and how to abandon Cronbach’s alpha and the route towards more comprehensive assessment of scale quality. European Health Psychologist, 16(2), 56–69. Price, E., Ottati, V., Wilson, C., & Kim, S. (2015). Open-minded cognition. Personality and Social Psychology Bulletin, 41(11), 1488– 1504. doi:10.1177/0146167215600528. Pykett, J., Lilley, R., Whitehead, M., Howell, R., & Jones, R. (2016). Mindfulness, behaviour change and decision making: an experimental trial. Birmingham: University of Birmingham. Rossi, J. S. (2012). Statistical power analysis. In: W. A. Schinka & W. F. Velicer (Eds.), handbook of psychology volume 2: Research methods in psychology (pp. 71–109). Hoboken: Wiley. Ruocco, A. C., & Direkoglu, E. (2013). Delineating the contributions of sustained attention and working memory to individual differences in mindfulness. Personality and Individual Differences, 54(2), 226– 230. doi:10.1016/j.paid.2012.08.037.

Mindfulness Shapiro, S. L., Brown, K. W., & Astin, J. (2011). Toward the integration of meditation into higher education: a review of research evidence. Teachers College Record, 113(3), 493–528. Spies, K., Hesse, F., & Hummitzsch, C. (1996). Mood and capacity in Baddeley’s model of human memory. Zeitschrift für Psychologie mit Zeitschrift für Angewandte Psychologie, 204(4), 367–381. Stanovich, K. E., & West, R. F. (1997). Reasoning independently of prior belief and individual differences in actively open-minded thinking. Journal of Educational Psychology, 89(2), 342–357. Teper, R., Segal, Z. V., & Inzlicht, M. (2013). Inside the mindful mind: how mindfulness enhances emotion regulation through improvements in executive control. Current Directions in Psychological Science, 22(6), 449–454. doi:10.1177/0963721413495869.

Tolentino, E., Curry, L., & Leak, G. (1990). Further validation of the short form of the need for cognition scale. Psychological Reports, 66(1), 321–322. doi:10.2466/PR0.66.1.321-322. Vago, D. R. (2014). Mapping modalities of self-awareness in mindfulness practice: a potential mechanism for clarifying habits of mind. Annals of the New York Academy of Sciences, 1307(1), 28–42. Verplanken, B., & Fisher, N. (2014). Habitual worrying and benefits of mindfulness. Mindfulness, 5(5), 566–573. doi:10.1007/s12671-0130211-0. Zeidan, F., Johnson, S. K., Diamond, B. J., David, Z., & Goolkasian, P. (2010). Mindfulness meditation improves cognition: evidence of brief mental training. Consciousness and Cognition, 19(2), 597– 605. doi:10.1016/j.concog.2010.03.014.