Why are we unable to walk straight and tend to lose our balance when we walk with our eyes closed?
ANSWER I: When one wants to walk in a straight line the brain takes a visual reference point and uses this reference point to maintain the movement in a straight line. In the absence of a visual reference point the brain is unable to ascertain the exact direction in which the body is moving and hence most of us will be unable to walk in a straight line with our eyes closed.
However visual reference is not the only mechanism of maintaining balance or direction in our movements. We can judge the direction of movement very accurately with the balance sense from the balance mechanism in our inner ear and by kinesthetic sense, which is sensations we derive from our muscles, joints and ligaments.
Both these sensations will tell us very accurately as to the balance and direction of movement and position of the body at any point of time. This is highly developed in acrobats, gymnasts and ice skaters. They would be able walk in a straight line even with their eyes closed.
ANSWER II: Human balance is maintained by three pillars namely vestibular system — balance organ in the inner ear and its connections — eye and proprioceptors in the joints of the body. Man can maintain balance with any two pillars but not with one pillar alone. Imagine a blind man who can walk without losing balance.
If the same person develops any disorder in the vestibular system or proprioceptive system, then he cannot stand or walk. Similarly if a normal person develops a disorder in the inner ear or proprioceptive system and tries to stand with eyes closed and feet together, he will lose balance.