METHOD

Subjects

14 children (6 female) with ages ranging from 12 to 17 years (group mean = 14.5, SD + 1.5 years) received 10 days training in a combination of yoga practices. A group of 14 age and sex matched children who did not receive training in yoga were followed up for comparison and to see the retest effect. All subjects had normal vision without correction and none of them had color blindness. The latter was measured in view of the fact that the color of the stimulus has been reported to influence the CFF (Ali, Jahan & Chowdary, 1986).

Design

Both groups (yoga and control) were assessed on Day 1 and Day 10. The yoga group was attending a 10-day residential yoga camp, while the control group carried on with their routine activities.

Assessments

(i) Critical Flicker Fusion Frequency (CFF): CFF was measured using a standard electronic apparatus (Fritze & Simonson. 1951) (Anand Agencies, Pune, India). This apparatus consists of a red stimulus (6 mm in diameter) in the center, with a luminous intensity of 50 mcd and flicker frequency, which can be, adjusted from 12 to 95 Hz. A white background with illumination of 150 lux surrounded the stimulus. The subject was seated at ease 50 cm in front of the apparatus (i.e., 80 cm from the stimulus). The experiment was conducted with a minimal illumination of a 40-w bulb fixed behind the subject and the light dark ratio was kept as 1 (50:50). The binocular response of all subjects was assessed in both ascending and descending trials as described, according to the standard methodology (Ramana et al., 1997').

(ii) Muller-Lyer Apparatus: The degree of optical illusion was measured using the Muller-Lyer apparatus (Anand Agencies, Pune, India). The Muller-Lyer lines though of equal length, appear unequal due to the two different types of arrows drawn at both ends of the line: closed-ended arrows making an acute angle or open-ended making an obtuse angle with the shaft. One line was of fixed length with close-ended arrows giving it an illusionary shorter appearance, while the length of the other line could be varied. This line had open-ended arrows giving it a longer appearance. The subjects were seated 1.8 m away from the apparatus, while the experimenter manipulated the length of the line according to the subject's specifications. The exact position at which the subject perceived the two lines to be of equal length was noted, i.e., subjective reading ("Sr"). The difference between the 'Sr' and the reading, at which the lines were actually of equal length, gave the degree of illusion ("di"). The degree of illusion perceived using Muller-Lyer lines in both ascending and descending trials were recorded using method described previously (Telles et al., 1997). Data al the end of 10 days were compared with initial data using the 't' test for paired data.

Yoga Training

The yoga group received yogic training for approximately 8 hours a day, aiming at their all round (physical, mental, intellectual and spiritual) development. The 10-day Program consisted of (1) Yogasanas, specialized physical postures; (2) Pranayama or voluntary regulation and slowing of the breathing: (3) Kriyas, internal cleansing practices including eye-cleansing techniques (trataka); meditation and bhajans. In addition to these specialized practices, the training also included games to improve the attention span and memory as well as telling of meaningful stories to foster a sense of values and feelings of responsibility (Telles et al., 1993).