London: Each child's brain is wired to underestimate the true amount of force he or she uses on others - while accurately perceiving the amount of force he or she receives, suggests a study by University College London (UCL) scientists.

Published in the journal 'Science', the study had lead author Sukhwinder S Shergill (UCL) and colleagues conducting a series of "tit-for-tat" experiments on pairs of test subjects. When subjects were asked to alternately press each others' fingers, using the same amount of force just applied to their own fingers, the amount of force escalated quickly.

A second experiment was performed in which subjects applied force via a joystick, rather than by direct contact. This test has been shown not to use the brain's predictive machinery. As predicted, the forces generated and received matched each other more accurately.

Shergill said, "The results showed that to get same feeling of force, you need to exert more force. So, when you apply force yourself by pushing with your finger it feels less than when you use a machine. It is well known that a system in the brain de-emphasises the effects of our own actions, but this is the first time it has been measured."

He added, "This mechanism also explains why you cannot tickle yourself - the brain already knows what sensation to expect and alters the brain activity responsible for the sensation accordingly. But when someone else tickles you there is no chance to adjust your brain perception, and you feel the full effects."

ANI