yogic visual concentration ( trataka ) is one of the six cleansing techniques mentioned in the ancient indian yogic text , hata yoga pradipika . 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 . 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 . 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 . the adult s version of the stroop color  word test was used to assess the cognitive function of the participants . 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 . if the participants made a mistake , they were asked to stop and proceed after correcting the mistake . a stop - watch was used to record the time taken to complete the task . 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 1 day and the control session was carried out on 2 day . participants were alternately allocated to either schedule to prevent the order of the sessions influencing the outcome . the theoretical aspects of trataka were explained by a qualified yoga teacher on the 1 day . 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 . palming consists of putting slightly cupped palms over the eyes , so that the eyes perceive complete darkness . the participants were asked to fix their gaze on the flame of a candle for approximately 23 minutes , suppressing the urge to blink as far as possible . finally , the participants were asked to defocus , and the practice ended with silence and prayer . 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 . 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 the pure interference score is calculated by subtracting the raw color score from the raw color 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 . the group mean and standard deviation for the scores obtained in the stroop color  word test are presented in table  1 . 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 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 . 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 . 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 ) . 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 . 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 ) . this suggests better selective attention , visual scanning , and concentration after the practice of dharana . in another study , 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 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 . 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 .
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 .