As well as qualifying the teary "she hit me harder" playground argument and explaining why we can't tickle ourselves, the discovery may provide insight into some self-delusional symptoms of schizophrenia.
To test the notion that the brain downplays sensations generated by body movements because it can predict what will happen, Daniel Wolpert and colleagues at University College London in the UK engaged six pairs of adult volunteers in "tit-for-tat" experiments.