Introduction
Ongoing research suggests mindfulness enhances executive function, although long-term interventions are time consuming and an unrealistic reflection of real-life. More recently, the benefits of short-term mindfulness have been highlighted, despite Anderson, Lau, Segal and Bishop (2007) observing no improvement in attentional control. This study aims to clarify the effect of short-term mindfulness on executive function and provide support for previous findings. A total of 98 participants listened to mindfulness meditation, mind-wandering meditation or an audiobook. Subsequently participants completed the Self-Assessment Mannikin (Bradley & Lang, 1994) to assess mood; Stroop (Stroop, 1935) and Simon task (LeMay & Simon, 1969) to test executive function and Five-Facet Mindfulness Questionnaire 15-item version (FFMQ-15; Baer et al., 2008) to produce a score reflecting mindfulness traits. It was predicted that Stroop interference would be smaller in the mindfulness condition, compared to the mind-wandering and audiobook controls. Paired sample t-tests calculated a significant difference for each condition, revealing a Stroop interference effect. Whilst a one-way between participants ANCOVA identified a non-significant main effect of group on Stroop interference, inferring the size of the Stroop interference effect did not differ between conditions once general mindfulness had been taken into account. FFMQ-15 scores were an added covariate to determine the influence of mindfulness traits, although the main effect was non-significant. Overall, the results were inconsistent with the majority of previous research. This study argues the need for further research to identify a potential mechanism and understand factors required to maximise the benefits of mindfulness in terms of executive function.
Mindfulness – for some a way of life and for others a waste of time. Kabat-Zinn (2003) defined mindfulness as the awareness that emerges through purposely paying attention to the present moment and unfolding of experience without judgement. Mindfulness can be achieved through meditation interventions that involve paying close and continuous attention to an object, and if awareness shifts away, return attention to the object. The most commonly practiced intervention is mindfulness of the breath, where individuals focus on the physical sensations of breath entering and leaving their body.
Many people disregard mindfulness, although research has highlighted the value of meditation. For instance, in reducing symptoms of binge eating (Kristeller & Hallett, 1999), improving mood (Speca, Carlson, Goodey & Angen, 2000) and enhancing relationships (Carson, Carson, Gil, & Baucom, 2004). Recently, research has investigated the effect of mindfulness on executive function – mental processes required for attention when relying on instinct would be inappropriate. Inhibitory control is a core executive function that involves managing one’s attention, behaviour, thoughts and emotions and allows us to override a strong internal predisposition or external stimulation to behave appropriately (Diamond, 2013). The Stroop task measures inhibitory control by assessing one’s ability to overcome the automatic process of reading and name the ink colour of a colour word. The Stroop interference effect occurs when a mismatch in stimuli delays response time, indicating cognitive interference (Stroop, 1935).
Research has demonstrated long-term mindfulness interventions can improve executive function. For example, Moore and Malinowski (2009) identified reduced Stroop interference in experienced Buddhist meditation practitioners, who self-reported high levels of trait mindfulness, compared to non-meditators. It was concluded that mindfulness was positively correlated with sustained attention via cognitive flexibility. Contrastingly, Riggs, Black and Ritt-Olsen (2015) found mindfulness was significantly associated with inhibitory control, but not cognitive flexibility. Jha, Krompinger and Baime (2007) concluded mindfulness improved attention-related behavioural responses by enhancing functioning of specific subcomponents of attention. Additionally, Teper and Inzlicht (2013) discovered long-term meditators made fewer errors on the Stroop task compared to a control group, although attributed findings to heightened emotional acceptance. This research suggests long-term mindfulness meditation can enhance inhibitory control, despite conflicting explanations of findings. However, extensive practice periods are impractical and an unrealistic reflection of real-life as the majority of people don’t have the time to commit.
Consequentially, research has investigated whether short-term meditation is valuable, or if long-term interventions are required to experience benefits. Wenk-Sormaz (2005) found brief meditation practice reduced habitual responding on the Stroop task. Meditation participants were better able to inhibit the automatic process of reading and focus on colour. Further, Zeidan, Johnson, Diamond, David and Goolkasian (2010) examined the influence of brief mindfulness training on mood and cognition compared to an audiobook control group. Sustained attention and executive function significantly improved, but there was no effect on mood. It was concluded that mindfulness meditation increased focus on timed or speeded tasks. However, Anderson, Lau, Segal and Bishop (2007) investigated the effect of short-term mindfulness training, psychological education and physical exercise on executive function. Results revealed enhanced emotional well-being, but no improvement in attentional control. Therefore, short-term mindfulness meditation has been shown to enhance executive function, although there are mixed results.
Due to inconsistent findings, it is essential to clarify the effect of short-term mindfulness meditation on executive function and provide support for previous research. Therefore, this experiment aims to investigate the effect of brief mindfulness meditation on executive function. Participants listened to mindfulness meditation, mind-wandering meditation or an audiobook. Following this, participants completed the Self-Assessment Mannikin (SAM; Bradley & Lang, 1994) to assess mood; Stroop and Simon task (LeMay & Simon, 1969) to test executive function and Five-Facet Mindfulness Questionnaire 15-item version (FFMQ-15; Baer et al., 2008). Only Stroop and FFMQ-15 data were analysed. FFMQ-15 scores were an added covariate to determine whether the effect of mindfulness on executive function was stronger if one’s initial mindfulness trait score was higher. Previous research has shown mindfulness to enhance attention and one’s ability to focus on a stimulus or ignore distracting stimuli. Correspondingly, mindfulness meditation should improve control over automatic behaviours and performance on executive function tasks. Therefore, it was predicted Stroop interference would be smaller in the mindfulness condition, compared to mind-wandering and audiobook controls.
Method
Participants
All 98 Swansea University Undergraduate Psychology students were recruited through opportunity sampling. The average age was 20.34 years (SD= 2.66) and the gender split was unequal (m=16, f=82). The sample had normal or corrected-to-normal vision and were not colour blind. Participants provided written consent and were not rewarded.
Design
The overall design of this study was a one-way ANCOVA. The Stroop task was based on a mixed design, manipulating two independent variables. The group was manipulated between-participants and had three levels – mindfulness, mind-wandering and control. In the Stroop task, congruency was manipulated within-participants and had three levels – congruent, incongruent and neutral. FFMQ-15 scores were an added covariate in the analysis. The dependent variable was response time.
Materials
In the Stroop task a central fixation cross appeared followed by a button with the message ‘Go’ that had to be selected to continue - ensured cursor was in the same starting location for each trial, controlling response time. The stimulus was printed in red, green, blue or orange and the participant selected the matching coloured button. There were 96 neutral (four X’s printed in one of the colours), 24 congruent (colour word printed in the same ink colour) and 72 incongruent trials (colour word printed in a different ink colour) split across four blocks (Stroop, 1935). In the Simon task participants were instructed to press a button with their right or left index finger according to the colour of a square, which appeared either side of a central fixation cross. In congruent trials the coloured square appeared the same side as the correct response hand, whereas in incongruent trials the coloured square appeared the opposite side to the correct response hand (LeMay & Simon, 1969). There were 60 congruent and 60 incongruent trials. Mood was assessed using the SAM (Bradley & Lang, 1994; appendix A), where participants rated happiness and excitement. The FFMQ-15 was used to produce trait mindfulness scores (Baer et al. 2008; appendix B). Participants were exposed to one of three listening tasks, lasting 15 minutes. The audiobook condition listened to the first chapter of ‘Harry Potter and The Philosopher’s Stone’ read by Stephen Fry. The other conditions listened to guided meditation used by Hafenbrack, Kinias and Barsade (2013). The mindfulness condition were instructed to focus on breathing and bring attention back to breathing if their mind wandered, whereas the mind-wandering condition allowed their mind to wander.
Procedure
Data collection and questionnaire administration was controlled using Gorilla (Anwyl-Irvine, Massonnié, Flitton, Kirkham & Evershed, 2019). To begin, participants were presented with the information sheet (appendix C), which outlined the purpose of the research, and provided informed consent (appendix D). Following this, participants completed the SAM (appendix A), before being randomly allocated to one of three listening tasks - mindfulness, mind-wandering or audiobook. After this, participants completed the SAM a second time, followed by the Stroop and Simon tasks – order was counterbalanced. Participants then completed the SAM again and the FFMQ-15 (appendix B), before being debriefed (appendix E). The experiment took approximately 45 minutes.
Results
It was predicted Stroop interference would be smaller in the mindfulness condition, compared to mind-wandering and audiobook controls.
The difference in response times between correctly answered neutral and incongruent Stroop trials produced Stroop interference response times (Stroop, 1935). FFMQ-15 scores were calculated following guidelines (Baer et al. 2008; appendix B). The z scores for Stroop interference and FFMQ-15 scores were used to identify outliers - data from one mindfulness and two audiobook participants were eliminated. The data was interval level and normally distributed according to skewness and kurtosis scores. A non-significant one-way ANOVA between group and FFMQ-15 scores suggested the covariate and dependent variable were unrelated. The data met the homogeneity of regression assumption, identifying a non-significant interaction between group and FFMQ-15 scores. Table 1 displays descriptive statistics for the mean and standard deviation.
Discussion
In this experiment participants listened to mindfulness meditation, mind-wandering meditation or an audiobook. Following this, participants completed the SAM, Stroop task, Simon task and FFMQ-15. It was predicted that mindfulness meditation would reduce Stroop interference. Paired sample t-tests revealed a significant difference for each condition. Whilst, an ANCOVA identified a non-significant main effect of group on Stroop interference and a non-significant main effect for the covariate of FFMQ-15 scores.
This experiment aimed to investigate the effect of brief mindfulness meditation on executive function. Significant paired sample t-tests indicated a Stroop interference effect. However, the non-significant ANCOVA implied the size of Stroop interference did not differ between conditions once general mindfulness has been taken into account. The finding, that mindfulness meditation did not influence executive function is consistent with Anderson, Segal and Bishop’s (2007) research, although inconsistent with the majority of research that identified brief mindfulness enhanced executive function (Wenk-Sormaz, 2005; Zeidan et al., 2010). Increased meditation practice and participants understanding the goal of executive function tasks may explain this discrepancy and could be applied to real-life. For example, in mindfulness apps by informing individuals of task goals to improve executive function.
The non-significant main effect of FFMQ-15 scores suggests the effect of mindfulness meditation on executive function was not influenced by initial mindfulness traits. This contradicts Moore and Malinowski’s (2009) observation that experienced Buddhist meditation practitioners had higher self-reported trait mindfulness. However, self-report measures are subject to bias and unreliable compared to the FFMQ-15 which Shallcross, Lu and Hays (2020) found to accurately identify levels of trait mindfulness. Despite Buddhist meditation practitioners being likely to have high levels of trait mindfulness due to lifestyle, this implies the effect of mindfulness on executive control is immediate and not influenced by internalised mindfulness traits. Given the non-significant findings, a potential mechanism by which mindfulness influences performance is difficult to identify. However, wider research has investigated alternative influential factors such as positive affect (Malinowski & Lim, 2015).
One limitation of this study may be the degree of participant engagement with the listening task. The experiment took place in a room amongst other participants with potential distractions, disrupting focus. This may have impacted performance on executive function tasks, particularly in the mindfulness condition as participants might not have been in the desired state.
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