Immediate effect of yogic visual concentration on cognitive performance.

The ancient Indian yoga text, Hatha Yoga Pradipika, describes six cleansing techniques. The objective of cleansing techniques is to purify and prepare the body for the practice of yoga postures, breath regulation, and meditation. Yogic visual concentration technique (trataka) is one of these techniques. A previous study showed an increase in critical flicker fusion (CFF) following yogic visual concentration (trataka). The present study planned to assess the immediate effect of trataka on cognitive performance using the Stroop color-word test. Performance on the Stroop color-word test was assessed in 30 healthy male volunteers with ages ranging from 18 years to 31 years old (22.57 ± 3.65 years). The participants were tested before and after yogic visual concentration (trataka) and during a control session on two separate days. There was a significant improvement in performance on the Stroop color-word test after trataka compared to the control session [repeated measures analysis of variance (RM ANOVA) with Bonferroni adjustment; p < 0.001]. Performance on the Stroop color-word test was better after trataka compared to the control session suggesting that the trataka technique increased the selective attention, cognitive flexibility, and response inhibition.

Introduction

Yogic visual concentration (trataka) is one of the six cleansing techniques mentioned in the ancient Indian yogic text, Hata Yoga Pradipika. The literal meaning of the Sanskrit word trataka is “to gaze steadily”. Looking intently with an unwavering gaze at a small point until tears are shed is known as trataka (Hata Yoga Pradipika, Ch:2, V: 31). Hata Yoga Pradipika mentions that the practice of trataka eradicates all eye diseases, fatigue, and lethargy (Hata Yoga Pradipika, Ch:2, V: 32). Although trataka is known as a cleansing technique, the final stage of trataka induces a meditative mental state. When meditation is practiced over a period of time it improves perception, attention, and cognition. A large number of research studies have shown improvement in attentional task performance following meditation.

The Stroop color–word test is a useful and reliable assessment tool used in psychology.4, 5 It was first described by John Ridley Stroop in 1935. It measures selective attention, cognitive flexibility, and reaction time. A study used Stroop color–word test to examine the differences in various domains of attention between long-term concentrative meditators versus matched controls. Performance on the Stroop test was significantly higher following long-term Vihangam meditation practice suggesting an increase in selective attention, cognitive flexibility, and processing speed.

Recently, a study was conducted to evaluate the immediate effect of trataka on critical flicker fusion (CFF). CFF is defined as the frequency at which a flickering stimulus is perceived to be continuous. Thirty healthy volunteers were assessed in two sessions, i.e., a trataka and a control session. There was a significant increase in CFF following trataka, suggesting changes at the cortical level in the processes that mediates fusion.

However, no studies evaluating the immediate effect of trataka on cognitive performance, suggesting that there are changes, exist. Hence, the present study was designed to assess the immediate effect of trataka on cognitive performance using the Stroop color–word test.

Materials and methods

Participants

Thirty male volunteers with ages ranging from 18 years to 31 years old (22.57 ± 3.65 years) were recruited for the study. They were all students of a yoga university in Southern India. Their health status was evaluated by a routine clinical examination and case history. They had normal health and were not taking any medication. The predetermined conditions to exclude participants from the trial were chronic illness, visual deformities, and color blindness. The project was approved by the institution’s ethics committee (Swami Vivekananda Yoga Anusandhana Samsthana (a deemed University) Bangalore). The study protocol was explained to the participants and their signed consent was obtained.

Assessment

The Adult’s version of the Stroop color–word test was used to assess the cognitive function of the participants. The test consists of three pages. The first page tests how fast the participant can read the words, the second page tests how fast the participants can name the colors on the page, and on the third page the participants were asked to name the color of the ink the individual words were printed in, ignoring the word itself for each item. The task was administered individually. If the participants made a mistake, they were asked to stop and proceed after correcting the mistake. The participants were given 45 seconds for each page. Detailed instructions were given to the participants before starting the test. A stop-watch was used to record the time taken to complete the task.

Design

A self-controlled study design was used. Each participant was assessed during two sessions (a trataka and a control session) on two separate days. Half of the participants practiced trataka on the 1st day and the control session was carried out on 2nd day. The remaining participants reversed the order of the sessions. Participants were alternately allocated to either schedule to prevent the order of the sessions influencing the outcome. The duration of both sessions was 25 minutes. Participants were assessed before and immediately after each session.

Intervention

Trataka

The participants were given 15 days of training in trataka. The theoretical aspects of trataka were explained by a qualified yoga teacher on the 1st day. Prerecorded audio instructions for trataka were played during the session. Trataka practice consists of two distinct stages. The first stage consists of eye exercises, which is a preparatory practice for trataka. The eye exercises include eyeball movements in horizontal, vertical, and diagonal directions and circular movements. These were performed with the eyes open, in a well-lit room. This was followed by the practice of palming to relax the eyes. Palming consists of putting slightly cupped palms over the eyes, so that the eyes perceive complete darkness. The first stage lasted for 10 minutes. The second stage was trataka, and it was practiced in a dark room. The participants were asked to fix their gaze on the flame of a candle for approximately 2–3 minutes, suppressing the urge to blink as far as possible. Then they were asked to visualize the candle flame in between the eyebrows. This process was repeated for two to three rounds. Finally, the participants were asked to defocus, and the practice ended with silence and prayer. The second stage lasted for 15 minutes. The duration of the whole practice was 25 minutes.

Control session

During the control session, the participants practiced eye exercises for 10 minutes, and then for the next 15 minutes, they sat quietly with their eyes closed without doing any concentration or meditation exercises.

Data extraction

The Stroop color–word test yields three basic scores, namely: (1) raw word scores; (2) raw color scores; and (3) raw color–word scores. The raw word score is the number of items completed on the word page, the raw color score is the number of items completed on the color page, and the raw color–word score is the number of items completed on the color–word page. The pure interference score is calculated by subtracting the raw color score from the raw color–word score.

Data analysis

Statistical analysis was carried out using SPSS (IBM Corporation, USA) (Version 19.0). Since the same individuals were assessed in repeat sessions on separate days (i.e., trataka and control), repeated measures analysis of variance (RM ANOVA) was used. Two-way RM ANOVA was performed using two 'within participants' factors, i.e., Factor 1: sessions; trataka and control and Factor 2: states; “pre”, and “post”. This was followed by a post-hoc analyses using Bonferroni adjustment to compare pre with post values.

Results

The group mean and standard deviation for the scores obtained in the Stroop color–word test are presented in Table 1.

Table 1

Scores in the Stroop color–word test before and after the control and trataka sessions.

Variables	Control		Trataka
Pre	Post	Pre	Post
Word score (W)	90.40 ± 17.62	94.40 ± 17.37 *	92.60 ± 14.88	107.07 ± 15.90 **,****
Change (%)		4.42 %↑		15.63%↑
Color score (C)	59.53 ± 9.23	63.67 ± 8.77 **	60.47 ± 9.19	71.10 ± 9.83 **,****
% Change (%)		6.95 %		17.58 %
Color–word score (CW)	39.60 ± 7.49	43.83 ± 7.23 **	38.77 ± 6.55	48.87 ± 6.94 **,***
Change (%)		10.68 %↑		26.05 %↑
Interference score (CW-C)	19.93 ± 5.95	19.8 3 ± 6.69	21.70 ± 6.40	22.23 ± 6.90

* p < 0.01; ** p < 0.001; RM ANOVA with Bonferroni adjustment comparing post values with pre values.

*** p < 0.01; **** p < 0.001; RM ANOVA with Bonferroni adjustment comparing post trataka with post control sessions.

RM ANOVA

Two-way RM ANOVA showed a significant difference between sessions for: (1) word score F (1, 29) = 21.57, p < 0.001; and (2) color score F (1, 29) = 9.65, p < 0.01. There was a significant difference between states for: (1) word score F (1, 29) = 163.42, p < 0.001; (2) color score F (1, 29) = 195.30, p < 0.001; and (3) color–word score F (1, 29) = 435.24, p < 0.001. Also, there was a significant interaction between the session and state for (1 word score F (1, 29) = 55.69, p < 0.001; (2) color score F (1, 29) = 29.61, p < 0.001; and (3) color–word score F (1, 29) = 54.90, p < 0.001.

Post hoc analyses with Bonferroni adjustment

Post hoc analyses with Bonferroni adjustment was performed and all comparisons were made using the respective “pre” states. There was a significant difference between the “post” session of trataka and of the control (p < 0.001). There was a significant increase in the word score (p < 0.001), color score (p < 0.001), and color–word score (p < 0.001) after trataka compared to before trataka. And also, there was a significant increase in the word score (p < 0.01), color score (p < 0.001), and color–word score (p < 0.001) after the control session compared to before. There was no significant difference in the interference score.

Discussion

In this study, Stroop color–word test was assessed before and after the practice of trataka and control sessions in 30 male volunteers. The Stroop color–word test is an index of executive functioning such as interference control, selective attention and cognitive flexibility, and response inhibition.9, 10, 11 Trataka showed better performance on the Stroop color–word test compared to the control session.

The Stroop color–word test consists of four basic scores, namely, the word score, the color score, the color–word score, and the interference score. The word score is the number of items completed on the word page and it reflects basic reading speed. The word score significantly increased following trataka (15.63%) compared to the control session (4.42%), suggesting better reading speed after trataka. Naming of a color takes more time than naming a word because it requires a conscious effort to choose and say the name of the color. The color score is the number of items completed on the color page and it involves selective attention. The color score significantly increased after trataka (17.58%) compared to the control session (6.95%), suggesting better selective attention following trataka. The color–word score is the number of items completed on the color–word page which involves naming the color of the ink the individual words are printed in, while ignoring the word that is printed for each item (i.e., the word “RED” printed in green ink). The scores on the color–word page were significantly higher following trataka (26.05%) compared to the control session (10.68%), suggesting better selective attention, cognitive flexibility, and response inhibition after trataka.

Trataka involves intense focusing on a candle flame. It is somewhat similar to a focused meditative state (dharana) which is described in the ancient yoga text, Patanjali Yoga Sutras. A study compared performance on a cancellation task following four mental states namely, cancalata (random thinking), ekagrata (nonmeditative concentration), dharana (focused meditation), and dhyana (effortless meditation or meditative expansiveness). Following dharana there was a significant increase in the scores on cancellation task. This suggests better selective attention, visual scanning, and concentration after the practice of dharana. In another study, the practice of dharana showed improvements in incidental learning, accuracy, and attention.

An earlier study on trataka showed a significant increase in CFF suggesting changes at the cortical level in the processes that mediates fusion. The findings of the present study are in line with this earlier study. In the current study, performance on the Stroop color–word test increased after trataka. Performance on the Stroop color-word test is related to the prefrontal cortex. Hence, improved performance on the Stroop color–word test after trataka may be due to the increased activity at the prefrontal cortex.

Though there was better performance after trataka compared to the control sessions there was a significant increase after the control session compared to presession scores. The control session consisted of 10 minute eye exercises, and for the following 15 minutes participants were asked to sit quietly with closed eyes without meditation. The participants may have practiced focused thinking or meditation during the control session and this may be the reason why there is an increase in the scores. However, this is just a speculation and no objective measurements were performed to confirm this.

One of the main limitations of the study is that there is no guarantee that each participant did not practice meditation or any focused thinking during the control session. It would have been ideal to have a simultaneous assessment of physiological parameters to assess the level of autonomic arousal during the two sessions. This is of particular interest because attention is known to modulate sympathetic activation.

Conclusion

Trataka showed better performance on the Stroop color–word test compared to the control session, suggesting increased selective attention, cognitive flexibility, and response inhibition following trataka. Further studies using other objective measurements would substantiate these findings and may help to understand the mechanisms involved.

Conflicts of interest

The authors declare that they have no conflicts of interest.