Other laboratory studies indicated that hypnosis does not act as a tranquilizer or as a placebo. Hypnotic analgesia is not reversed by naloxone, an opiate antagonist, so it is not mediated by the release of endogenous opiates. A series of studies by K.S. Bowers attempted to determine whether hypnotic analgesia is mediated by stress-inoculation strategies of the sort proposed by Spanos. Moreover, response to hypnotic analgesia suggestions was mediated by hypnotizability, while response to stress-inoculation instructions was not. Taken together, these studies show that stress inoculation can reduce pain, but it does not mediate pain reduction in hypnotic analgesia.
Hypnotic analgesia appears to illustrate the dissociation between explicit and implicit perception.
Studies of hypnotic deafness, hypnotic blindness, and negative hallucinations also appear to illustrate the dissociation between explicit and implicit perception in the visual and auditory domains. These findings are consistent with the notion of an amnesia-like barrier which alters conscious awareness while permitting subconscious processing to continue, as suggested by Hilgard's neodissociation theory of divided consciousness. The laboratory phenomena of hypnosis, like the clinical symptoms of genuine cases of dissociative and conversion disorders, expand the boundaries of the psychological unconscious beyond the automatic and the preconscious. As suggested by Prince, Janet, Sidis, James, and Hilgard, the psychological unconscious also includes a category of sub conscious processing including cases where conscious perception fails despite supraliminal stimulation and focused attention, conscious memory fails despite adequate encoding and storage, and complex, deliberate, attention-demanding behaviors are experienced as automatic.