Still other investigators have sought to uncover distinct physiological markers of hypnosis. Under hypnosis, EEGs, especially those of highly suggestible participants, sometimes display a shift toward heightened activity in the theta band (four to seven cycles per second). In addition, hypnotized participants frequently exhibit increased activity in their brain’s anterior cingulate cortex (ACC).
Yet neither finding is surprising. Theta activity is typically associated with states of quiet concentration, which frequently accompany hypnosis. The ACC is linked to the perception of contradictions, which many hypnotized participants experience as they imagine things—such as childhood experiences in the present—that seem to conflict with reality. Further, psychologists have reported similar brain changes among awake subjects. For example, the ACC becomes activated during the famous Stroop task, which requires subjects to name the colors of ink (such as “green”) in which competing color words (such as “blue”) are printed. Thus, these brain changes are not unique to hypnosis.
Fueling the perception of hypnosis as a distinct trancelike state is the widespread assumption that it leads to marked increases in suggestibility, even complete compliance to the therapist’s suggestions. Nowhere is this zombielike stereotype portrayed more vividly than in stage hypnosis shows, in which people are seemingly induced to bark like dogs, sing karaoke and engage in other comical behaviors in full view of hundreds of amused audience members.
Yet research shows that hypnosis exerts only a minor impact on suggestibility. On standardized scales of hypnotic suggestibility, which ask participants to comply with a dozen suggestions (that one’s arm is raising on its own power, for example), the increase in suggestibility following a hypnotic induction is typically on the order of 10 percent or less. Moreover, research demonstrates that a formal hypnotic induction is not needed to produce many of the seemingly spectacular effects of hypnosis, such as reduction of extreme pain or various physical feats, popular in stage hypnosis acts, such as suspending a participant horizontally between the backs of two chairs. One can generate most, if not all, of these effects merely by providing highly suggestible people with sufficient incentives to perform them. Stage hypnotists are well aware of this little secret. Before beginning their shtick, they prescreen audience members for high suggestibility by providing those people with a string of suggestions. They then handpick their participants from among the minority who comply.
We agree with Lynn and psychologist Irving Kirsch of the University of Hull in England, who wrote in 1995 that “having failed to find reliable markers of trance after 50 years of careful research, most researchers have concluded that this hypothesis [that hypnosis is a unique state of consciousness] has outlived its usefulness.” Increasingly, evidence is suggesting that the effects of hypnosis result largely from people’s expectations about what hypnosis entails rather than from the hypnotic state itself. Still, it is always possible that future studies could overturn or at least qualify this conclusion. In particular, research on potential physiological markers of hypnosis may elucidate how hypnosis differs from other states of consciousness. Although hypnosis poses fascinating mysteries that will keep scientists busy for decades, it seems clear that it has far more in common with everyday wakefulness than with the watch-induced trance of Hollywood crime thrillers.
Note: This article was originally printed with the title, "Altered States".