i believe it is the involuntary action of the human muscle which is associated with the muscles linking the human ear drum with the nerves connected to the brain.so if thier is to be a wink it must be attached to the two ears.lekansigbeku

Bilateral symmetry is the default mode for movement. Infants suck, cry and wave their arms symmetrically and must eventually learn to do things one-sided. I have heard youngsters complain that they can't wink: when they try, they close both eyes. Even as adults, it is easier to do mirror-writing with your left hand if you simultaneously write the same word with your right. I, too, could once wiggle my ears only both at once. With practice I learned to wiggle one at a time, an accomplishment of no value to anyone - until now.

Spencer Weart, Hastings-on-Hudson, New York, US

Some combined bodily actions share neural channels, which prevent independent action. It is hard, for example, to direct your eyes independently. Physically it should be possible, but your mental control specialises in binocular coordination.

As a rule, independent direction of sensory organs is suited to detecting prey or danger, while symmetrical sensing permits precise measurement.

Most primates use their ears to supplement binocular vision or for direction finding. This means that not many need to move their ears much and hardly any need to move them independently; instead they move their heads.

Correspondingly, visual ear signals such as twitching, vital to most carnivores and many herbivores, hardly figure in the social behaviour of primates, especially the anthropoids. Our legacy is generally symmetrical.

Jon Richfield, Somerset West, South Africa

In order to wiggle one ear at a time, practice is needed in front of a mirror. That is how I learned the art. By grinning forcefully and widely, the ears are made to move. If you concentrate on finding the muscles that move the ears, you can operate them without grimacing. Then practise moving each ear by itself. What use does this skill have? It impressed teenage girls, up to a point, and a by-product was the smoothing out of wrinkles on my forehead.

Brian Colless, Palmerston North, New Zealand