"If a healthy person murmurs to himself, he knows that he is hearing his own voice," Flanagan said. "Now imagine that the person has a deficit in the predictive mechanism. He murmurs and then suddenly hears murmuring but cannot label it as himself. As he tries to make sense of the alien voice, the explanation for it could be quite bizarre, such as thinking it is coming from a wall or the pavement."

He is not certain whether some schizophrenics can tickle themselves, but since their falsely alien sensations often are accompanied by feelings of fear and paranoia, it is likely that the experience would not be pleasurable.