Newberg's scans showed that neural activity decreases in a region at the top and rear of the brain called the posterior superior parietal lobe. Newberg refers to this region as the orientation-association area, because it helps us orient our bodies in relation to the external world. Patients whose posterior superior parietal lobes have been damaged often lose the ability to navigate through the world, because they have difficulty determining where their physical selves end and where the external world begins. Newberg hypothesizes that suppressed activity in this brain region (prompted by an individual's willed activity) could heighten a sense of unity with the external world, thus diminishing a person's sense of subject-object duality.

Intriguingly, Newberg has found some overlap between the neural activity of self-transcendence and of sexual pleasure. This result makes sense, Newberg says. Just as orgasms are triggered by a rhythmic activity, so religious experiences can be induced by dancing, chanting, or repeating a mantra. And both orgasms and religious experiences produce sensations of bliss, self-transcendence, and unity; that may be why mystics such as Saint Teresa so often employed romantic and even sexual language to describe their raptures.


Compared with the brain's normal state (left), brain scans by Andrew Newberg of a buddhist in meditation (right) show decreased activity in the parietal lobes.

Courtesy of Andrew Newberg, M.D.

The overlap between rapture and orgasm isn't total. The hypothalamus, which regulates both arousal and quiescence, seems to play a larger role in orgasms, while the brain's frontal lobes, the seat of higher cognitive functions, are apparently more active during spiritual practices. Nevertheless, Newberg concludes, an "evolutionary perspective suggests that the neurobiology of mystical experience arose, at least in part, from the mechanism of the sexual response."

Newberg's research can be questioned on several counts, however. One might ask what his brain scans are really measuring, since his subjects must remain self-aware enough to pull a string when they reach what is allegedly their deepest state of spirituality. Also, the SPECT method provides only a snapshot of the brain at a single moment. Studies of meditation carried out with other techniques, such as magnetic resonance imaging and electroencephalography, have revealed different patterns of neural activity—not surprisingly, since meditation is a complex behavior that evokes many different psychological states.

Persinger, the neuroscientist whom Richard Dawkins visited in Sudbury, Ontario, attempts to explain religious experiences with a radically different theory, one with a pathological slant. Our sense of self, Persinger notes, is ordinarily mediated by the brain's left hemisphere—specifically, by the left temporal lobe, which wraps around the side of the head. When the brain is mildly disrupted—by a head injury, psychological trauma, stroke, drugs, or epileptic seizure—our left-brain self may interpret activity within the right hemisphere as another self, or what Persinger calls a "sensed presence." Depending on our circumstances and background, we may perceive a sensed presence as a ghost, angel, demon, extraterrestrial, or God. Religion (or at least the experience of God), Persinger's research suggests, might be a cerebral mistake.

Persinger was inspired in part by the Canadian neurosurgeon Wilder Penfield, who studied epileptic patients in the 1950s. While preparing them for brain surgery, Penfield stimulated different brain regions with electrodes and asked the patients to describe any sensations that resulted. (Because the brain has no pain receptors, patients undergoing brain surgery need not be knocked out with general anesthesia.) Some patients, when their temporal lobes were stimulated, reported hearing voices and seeing apparitions—not overtly religious experiences, necessarily, but certainly mysterious ones. After learning about Penfield's experiments, the British author Aldous Huxley wrote: "Is there, one wonders, some area in the brain from which the probing electrode could elicit Blake's Cherubim. . . ?"

Persinger wondered the same thing, and he has tried to answer Huxley's question by building a device consisting of solenoids that encircle the head and deliver computer-controlled electromagnetic pulses to specific regions of the brain. Persinger has tested the machine on 600 subjects, and he claims that as many as 80 percent "sense a presence" while they are being stimulated, compared with 15 percent of a control group.

Critics point out that Persinger's subjects usually know in advance how the God machine is supposed to affect them and hence might be only responding to suggestion. A group at Upp­sala University in Sweden recently found that subjects lacking such expectations experience no unusual psychological effects as a result of electromagnetic brain stimulation. Persinger counters that in at least two of his studies, suggestibility could not have been responsible, and the Swedes "didn't use our equipment properly."

Dawkins, when he visited Persinger's lab, experienced a slight dizziness and twitching in a leg but otherwise "nothing unusual." And Charles Cook, a former grad student of Persinger's who supervised God-machine sessions in the 1990s, has noted that most subjects who sensed a presence typically experienced only a vague feeling of being watched—which they were, of course, by the researchers.

The God Gene

Dean Hamer, head of gene structure and regulation at the National Cancer Institute, is endeavoring to link religion to a specific gene.

In the 1980s, a team at the University of Minnesota carried out a study of 84 pairs of twins—53 identical and 31 fraternal—who had been raised separately. The study was the first to suggest a genetic component to what the researchers called "intrinsic religiousness," which includes the tendency to pray often and to feel the presence of God.

Hamer sought to build on these findings by linking religiousness to a specific stretch of DNA. Hamer, an agnostic who emphasizes that his research is compatible with belief in God, began his search in the late 1990s, when he assembled 1,000 subjects for a study of the genetics of nicotine addiction. Hamer gave participants a detailed questionnaire, one section of which asked them to rate their feelings of absentmindedness, connectedness with nature, belief in extrasensory perception, and other traits. These questions, Hamer contends, provide a measure of the subjects' affinity for spirituality, akin to the trait that the Minnesota group called intrinsic religiousness.