Can hypnosis make you ticklish? Using suggestion to modulate agency

Sense of agency is the subjective sense of control we have over our actions. According to comparator model accounts, this arises when the predicted sensory effects of movements match actual sensory feedback. A consequence of this matching is sensory attenuation of self generated actions. This explains why, typically, we cannot tickle ourselves. Mechanically manipulating the sensory consequences of actions, however, can create a mismatch and the illusion that they are externally-produced; i.e., self-tickling becomes ticklish. Across three experiments, we aimed to create similar alterations in agency using hypnosis. We compared different suggestions - based on real world examples of agency disruptions - for participants of different levels of hypnotisability, with and without a hypnotic induction. We found that suggestions designed to model self-monitoring deficits increased perceived tickliness. These effects were stronger in high hypnotisable participants and after an induction. Demand characteristics explained behavioural but not subjective responses to tickling.