New research has it that our urge to imitate others is so well imprinted in our subconscious that it's almost impossible to control.
Psychologists who made the discovery say the unconscious desire to mimic is so powerful, it occurs even when people know they will be penalized for drawing a game.
In a series of experiments they found that people playing the schoolyard game rock-paper-scissors are far more likely to end the game in a "draw"-because of copying the hand gestures of their opponents.
"From the moment we're born, we are frequently exposed to situations where performing an action accurately predicts seeing the same action, or vice versa," the Daily Mail quoted Richard Cook, from University College London, as saying.
"Parents seemingly can't help but imitate the facial expressions of their new borns - smiling, sticking their tongues out and so on."
"This experience causes the impulse to imitate to become so ingrained it is often subconscious," he added.
Automatic copying is though to be controlled by a network of brain regions called the "mirror neuron system". The system responds immediately to the sight of any action - often before the conscious brain clocks what is happening.
Some evolutionary psychologists believe that automatic imitation may act as "social glue" - helping people to empathize and connect with each other.