Optical illusions test cognitive skills by challenging perception and observation. Finding four hidden faces in a picture within 8 seconds signifies elite observational abilities. Techniques like relaxing eyes, adjusting distance, scanning for patterns, and using peripheral vision can help reveal hidden elements. Optical illusions test cognitive skills by challenging perception and observation. Finding four hidden faces in a picture within 8 seconds signifies elite observational abilities. Techniques like relaxing eyes, adjusting distance, scanning for patterns, and using peripheral vision can help reveal hidden elements. Health and Fitness, Health Tips, Exercises & Workout Tips, Diet & Wellness | Times of India Lifestyle