Research findings on post-hypnotic suggestion,
As one would expect, the probability that subjects will respond to a posthypnotic suggestion is positively correlated with their measured hypnotic susceptibility, and susceptible subjects do experience a certain compulsion to respond (Barnier & McConkey 1998).
Some theories of hypnosis (e.g. that of Woody & Bowers 1994) may explain this in terms of the subject’s loss of executive control over the stipulated response, so that it is executed in automatic fashion. However, this kind of explanation may be of less cogency in the context of treatment, in which the posthypnotic response may first occur hours or even days after the session of therapy.
Moreover, studies (e.g. Barnier & McConkey 1998) indicate also that responding to posthypnotic suggestion involves the active participation of the subject, who must be motivated and prepared and feel expected to respond. Also, in laboratory studies, subjects do not always respond when they are not under the surveillance of the experimenter (Spanos et al 1987).
Heap, M., Aravind, K. (2002). Hartland’s medical and dental hypnosis (4th edition). London: Harcourt