ABSTRACT
Tickling is a common, perhaps universal, experience. Tickling someone often causes people to smile and laugh in a way that is indistinguishable from the laughter caused by being highly amused. Tickling usually occurs only between people who know each other well: children are likely to be tickled by their parents and siblings, adults are likely only to be tickled by their lovers. Internal 'forward models' mimic aspects of the external world and the motor system in order to capture the forward or causal relationship between actions and their outcomes. Forward models make predictions about the sensory consequences of self-generated movements on the basis of the efference copy generated in parallel with the motor command. Christopher D. Frith proposed that a defect in the central self-monitoring mechanism might underlie auditory hallucinations and passivity phenomena, which are 'first rank' features in schizophrenia. Auditory hallucinations normally consist of hearing spoken voices.
