Introduction
Inhibitory control of an ongoing action is critical for survival. Additionally, Moffitt et al. (Reference Moffitt, Arseneault, Belsky, Dickson, Hancox, Harrington, Houts, Poulton, Roberts, Ross and Sears2011) reported children with low self-control scores experience various socioeconomic problems later in life. While increased mindfulness may potentially result in better self-control, to date, few studies have explored its effects on motor inhibition. A potentially useful task for this is the go-stop paradigm (Heeren et al., Reference Heeren, Van Broeck and Philippot2009). However, this has limitations, including confounds with short-term memory and a potentially high probability of having to withhold a response. An alternative, the stop signal task (Logan, Reference Logan1994), has only imperative signals, such as arrows, with stop trials differing from go signals in that the imperative signal is followed by a visible indicator as the stop signal. Performance on this task is explained by a ‘horse-race’ model that assumes that there is a competition between pre-potent go and stopping responses to reach the threshold and determining the response.
Objective
A within subject, pre-test versus post-test design was employed, with effects of brief mindfulness induction compared to effects of a well-controlled resting state and an active control in which participants listened to their favorite music. It was predicted that the participants’ speed on an imperative go-signal (Go-RT) would be faster for post-test versus pre-test due to a practice effect. The primary measure of inhibitory control, stop signal reaction time (SSRT) was predicted to be shorter in the post-test condition following brief mindfulness induction in comparison to both the resting and preferred music conditions, indicating better motor inhibition facilitated by mindfulness.
Methods
Thirty participants (13 females) were recruited from the National Central University with a mean age of 23.1 (SD = 2.2) years. None had any prior meditation experience nor any neuropsychiatric disorder or current medication. All participants gave written informed consent in accordance with the Declaration of Helsinki and all experimental procedures were approved by the Institutional Review Board of National Taiwan University, Taipei, Taiwan. The stop signal task (see Figure 1) was performed by each participant in a pre-test and a post-test for three different conditions, each on different days (Figure 2). These conditions were resting state, listening to preferred music and engagement in mindfulness induction, all 20-minute duration. Resting state involved sitting idle, the music condition involved listening to their favorite music on their cellphones and for the mindfulness condition they followed instructions presented via a Power Point file (for details see Supplementary Document (dx.doi.org/10.17504/protocols.io.74ihque)).
Figure 1. Stop Signal Task.
Figure 2. Study Design
Results
Two participants were excluded, having RTs greater than ±3SD from the mean. Two-way repeated measures ANOVA was used for Go-RTs and SSRTs. Go-RTs showed no significant effect of condition [F(2, 54) = 0.121, p = 0.886] or condition x session interaction [F(2, 54) = 1.275, p = 0.288], but a significant effect of session [F(1, 27) = 13.150, p = 0.001]. Ad hoc pair-wise t-tests showed improvement across sessions for resting and mindfulness conditions, but not for the music condition [t(27) = 1.176, p = 0.250] (Figure 3). SSRTs showed no significant effect of condition [F(2, 54) = 0.371, p = 0.692], session [F(1, 27) = 1.385, p = 0.250], or interaction between condition and session [F(2, 54) = 0.946, p = 0.395]. Ad hoc paired-tests showed the mindfulness condition resulted in lower SSRTs that approached significance for post-test versus pre-test [t(27) = 1.868, p = 0.073] (Figure 4).
Figure 3. Go-RTs across conditions and sessions.
Figure 4. SSRTs across conditions and sessions.
Discussion
Post-test Go-RTs in mindfulness and resting condition showed an expected practice effect (Ando et al., Reference Ando, Kida and Oda2002). However, no such speed enhancement was seen for the preferred music condition. It is possible that the music listening may have caused emotional and physiological arousal (Rickard, Reference Rickard2004). Droit-Volet et al. (Reference Droit-Volet, Bueno and Bigand2013) found altered time perception due to emotional effects of music, mainly regulated by the temporal dynamics of the music. A marginal trend for slower SSRTs in the post-test session for the mindfulness condition might be linked with facilitated inhibition could be due to a lack of statistical power.
Conclusion
Consistent with a prior longitudinal study comparing mindfulness meditators and matched controls (Heeren et al., Reference Heeren, Van Broeck and Philippot2009), no difference in motor inhibition was observed here for the mindfulness condition compared to the two control conditions. The data obtained here are consistent with motor inhibitory control being unaffected by mindfulness, irrespective of whether engagement with the technique is long or brief. Future mindfulness studies should investigate a broader spectrum of cognitive tasks and sample populations (Jaiswal et al., Reference Jaiswal, Tsai, Juan, Liang and Muggleton2018) to test cognitive functions and population types that might be sensitive to mindfulness interventions.
Author Contributions
SJ and NGM conceived and designed the study. SJ conducted data gathering. SYT and WKL assisted in statistical analyses. SJ, NGM and CHJ wrote the article.
Funding
This work was sponsored by the Ministry of Science and Technology, Taiwan (grant numbers: 107–2420-H-008-009-; 108–2639-H-008-001-ASP; 108–2321-B-075 -004 -MY2;107–2628-H-008 -002 -MY3; 106–2410-H-008-038-MY3; 106–2628-H-008-002-MY4; 107–2410-H-008 -040 -MY3) and sponsored by Taiwan Ministry of Education’s “Academic Strategic Alliance: Taiwan and Oxford University” project grant (MOE Oxford- NCU-BRC collaborative project).
Conflicts of Interest
The authors have none to declare.
Data Availability
The dataset can be accessed at Zendo using the doi provide below: https://doi.org/10.5281/zenodo.3483190
Supplementary Materials
To view supplementary material for this article, please visit http://dx.doi.org/10.1017/exp.2020.29.
Open access
Comments
Comments to the Author: The authors present the results of an experiment comparing pre and post response times to go- and no-go-type tasks before/after three, 20-min conditions: resting control, mindful meditation and active control/listening to music. Post-condition reaction time was significantly reduced in the control and meditation conditions for the go task only. The experiment provides novel experimental support for prior meditation/reaction time studies. Strengths of the study include using meditation-naive participants, counterbalancing conditions, and including a concise and clear manuscript and supplemental files. Specifying the number of pre and post-task trials for each task, relevant effect sizes, and reporting any subjective feedback from participants about the conditions (for example, rating the experience of meditation, rest or music) may be helpful for additional interpretation. One challenge to interpreting the null results in the active control condition is the unstandardized format of the music condition. For example, music was self-selected by participants and played on cell phones. Specifying control for volume, speakers/earphones, number of songs and emotional content could additionally help in interpreting the results. An additional brief explanation of the role of the music condition in the study (as a form of active control) might also be helpful. Overall, the results of this paper help strengthen the understanding of mindfulness meditation on motor inhibitory control.