Five researchers take science where it's never gone before.

Three years ago, the British evolutionary biologist Richard Dawkins became a guinea pig in an experiment. Neuroscientist Michael Persinger claimed he had induced religious experiences in subjects by stimulating specific regions of their brains with electromagnetic pulses. Dawkins, renowned for his biological theories as well as for his criticism of religion, volunteered to test Persinger's electromagnetic device—the "God machine," as some journalists dubbed it. "I've always been curious to know what it would be like to have a mystical experience," Dawkins said shortly before the experiment. Afterward, he admitted on BBC that he was "very disappointed" that he did not experience "communion with the universe" or some other spiritual sensation.

Many researchers, like Persinger, view the brain as the key to understanding religion. Others focus on psychological, genetic, and biochemical origins. The science of religion has historical precedents, with Sigmund Freud and William James addressing the topic early in the last century. Now modern researchers are applying brain scans, genetic probes, and other potent instruments as they attempt to locate the physiological causes of religious experience, characterize its effects, perhaps replicate it, and perhaps even begin to explain its abiding influence.

The endeavor is controversial, stretching science to its limits. Religion is arguably the most complex manifestation of the most complex phenomenon known to science, the human mind. Religion's dimensions range from the intensely personal to the cultural and political. Additionally, researchers come to study religious experiences with very different motives and assumptions. Some of them hope that their studies will inform and enrich faith. Others see religion as an embarrassing relic of our past, and they want to explain it away.

"Even when the neural basis of religion has been identified, it remains a plausible interpretation of any conceivable neuropsychological facts that there is a genuine experience of God," notes Fraser Watts, a psychologist and theologian at the University of Cambridge and an Anglican vicar. A major funder of research on religion is the John Templeton Foundation, started in 1987 by the Christian financier John Templeton to promote "collaboration" between science and religion.

The theories described below illustrate the diversity of scientific approaches to understanding religion. All these theories are tentative at best, and some will almost certainly turn out to be wrong. The field suffers from vague terminology, disagreement about what exactly "religion" is, and which of its aspects are most important. Does religion consist primarily of behaviors, such as attending church or following certain moral precepts? Or does it consist of beliefs—in God or in an afterlife? Is religion best studied as a set of experiences, such as the inchoate feelings of connection to the rest of nature that can occur during prayer or meditation? Comparing studies is often an exercise in comparing apples and oranges. Nonetheless, the science merits close attention.

Inventing God

Stewart Guthrie, an anthropologist at Fordham University in New York, is in the explain-it-away camp of researchers. Noting the plethora of gods that populate the world's religions, many with minds and emotions similar to our own, Guthrie argues that the belief in supernatural beings is a result of an illusion that arises from our tendency to project human qualities onto the world. Religion "may be best understood as systematic anthropomorphism," he writes in his book, Faces in the Clouds.

Anthropomorphism is an adaptive trait that enhanced our ancestors' chances of survival, he adds. If a Neanderthal mistook a tree creaking outside his cave for a human assailant, he suffered no adverse consequences beyond a moment's panic. If the Neanderthal made the opposite error—mistaking an assailant for a tree—the consequences might have been dire. In other words, better safe than sorry. Over millennia, as natural selection bolstered our unconscious anthropomorphic tendencies, they reached beyond specific objects and events to encompass all of nature, goes Guthrie's theory, until we persuaded ourselves that "the entire world of our experience is merely a show staged by some master dramatist."

Humans are not alone in this trait. In The Descent of Man, Charles Darwin noted that many "higher mammals" share the human propensity "to imagine that natural objects and agencies are animated by spiritual or living essences." As an example, he recalled watching his dog growl at a parasol lifted off the ground by a gust of wind.

Andrew Newberg, a neuroscientist at the University of Pennsylvania, has focused on the tendency of people from different religious traditions to report similar mystical experiences, which typically involve sensations of self-transcendence and "oneness." These commonalities indicate that the visions stem from the same neural processes, Newberg hypothesizes. To test his theory, Newberg has scanned the brains of more than 20 adherents of spiritual practices, including Christian prayer and Tibetan Buddhist meditation. He uses a technique called single- photon-emission-computed tomography, or SPECT, a variant of the better-known positron-emission tomography, PET.

The chief advantage of SPECT is that it can capture the brains of meditators in a relatively natural setting. The subject meditates not in the SPECT chamber itself but in a separate room. When a subject—a Franciscan nun, in one case—feels her ordinary self "dissolving into Christ consciousness," as she describes it, a radioactive fluid is injected into her body through an intravenous tube; the fluid travels to her brain and becomes trapped in nerve cells there. The nun then goes to the SPECT chamber, where a computer-controlled camera scans her brain. The resulting image reveals levels of neural activity in the moment immediately after she received the radioactive fluid, when she presumably was still immersed in contemplation.

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.

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 Upp sala 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.

Hamer focused on genes associated with neurotransmitters called monoamines. The monoamines, which include serotonin and dopamine, help to regulate mood, among other functions. Psychiatric drugs such as Prozac and Thorazine affect monoamines, as do psychedelic drugs such as LSD, psilocybin, and mescaline, which can produce mystical visions.

Eventually Hamer found a variant, or allele, of a gene called VMAT, that corresponded to higher scores for what he had defined as spirituality. VMAT stands for vesicular monoamine transporter. The gene manufactures a protein that binds monoamines into packages, called vesicles, for transportation between neurons. Hamer calls the VMAT variant "the spiritual allele," or more dramatically, "the God gene" (also the title of his book)—even though according to his own statistics, it accounts for only 1 percent of the variance in the test scores of his subjects. Francis Collins, head of the Human Genome Project and a devout Christian, calls Hamer's claim "wildly overstated."

Rick Strassman has proposed a theory even more reductionist and far-fetched than Hamer's, yet one that has empirical support. Strassman, a psychiatrist in New Mexico, traces spirituality to a single compound, dimethyltryptamine, or DMT. In his book DMT: The Spirit Molecule, Strassman proposes that DMT secreted by our own brains plays a profound role in human consciousness. Specifically, he hypothesizes that endogenous DMT triggers mystical visions, psychotic hallucinations, alien-abduction experiences, near-death experiences, and other exotic cognitive phenomena.

First synthesized by a Canadian chemist in 1931, DMT is the primary active ingredient of ayahuasca, a hallucinogenic tea ingested as a sacrament by Amazonian Indians and by members of two churches in Brazil. (Although DMT is a controlled substance, the U.S. Supreme Court ruled earlier this year that members of a church in New Mexico can ingest ayahuasca for religious purposes.) Pure DMT normally has no effect when consumed orally, because an enzyme in the gut renders it inactive. But in the 1950s Stephen Szara, a Hungarian chemist who later worked for the National Institute on Drug Abuse, discovered that when injected, DMT triggers an extremely powerful hallucinogenic trip lasting less than an hour.

Like the classic psychedelic compounds LSD, mescaline, and psilocybin, DMT resembles neurotransmitters such as serotonin. But what makes DMT unique among the known psychedelics is that trace amounts of it naturally occur in the human body. Scientists first isolated DMT in human blood in 1965, and in 1972 a group led by the Nobel laureate Julius Axelrod of the National Institutes of Health detected the compound in human brain tissue.

These discoveries led to speculation that endogenous DMT—perhaps produced in excess or improperly regulated by the body—contributes to schizophrenia and other mental illnesses. By the early 1980s, the DMT theory of psychosis was largely abandoned when psychedelic research involving humans became too controversial. But in 1990, arguing that DMT merited further investigation, Strassman obtained permission from federal authorities to inject the drug into human volunteers.

A Zen Buddhist, Strassman was intrigued by the possibility that endogenous DMT plays a role in triggering mystical experiences. He suspected that DMT might be produced in the pineal gland, a minute organ nestled deep in the brain. The pineal gland abounds both in chemical precursors of DMT, such as tryptophan, and in beta-carbolines, the same compounds that render DMT orally active in the South American brew ayahuasca by counteracting the enzyme in the gut that breaks down DMT. From 1990 to 1995, Strassman supervised more than 400 DMT sessions involving 60 volunteers at the University of New Mexico. These were the first sanctioned psychedelic experiments involving human subjects in the United States since the mid-1970s.

To a certain extent, the DMT sessions fulfilled Strassman's expectations. Many of his subjects reported quasi-religious sensations of bliss, ineffability, timelessness, and reconciliation of opposites; a certainty that consciousness continues after death of the body; and contact with "a supremely powerful, wise, and loving presence." Others underwent classic near-death experiences, feeling themselves leaving their bodies and moving through a tunnel toward a radiant light.

Volunteers also reported visions that did not fit neatly into Strassman's scientific or spiritual worldview, however. Forty-seven percent encountered otherworldly beings, variously described as clowns, elves, robots, insects, E.T.-style humanoids, or "entities" that defied description. These bizarre beings were not always friendly. One of Strassman's subjects claimed to have been eaten alive by insectoid creatures. In part out of concern about this negative experience, Strassman discontinued his research.

Science cannot tell us if God exists only in our imaginations or as an entity beyond our comprehension. So why do some scientists continue the search for the roots of religious experience? Shouldn't such claims of oneness with a God be judged by their fruits, rather than their roots, as William James wrote in The Varieties of Religious Experience? Researchers may persist at these efforts because such studies offer the potential to alter our lives. In principle, these findings could lead to methods—call them "mystical technologies"—that reliably induce the state of spiritual insight that Christians call grace and Buddhists, enlightenment. Already Todd Murphy, a neuroscientist who has worked with Persinger, is marketing the "Shakti headset," a stripped-down version of Persinger's God machine, for "consciousness exploration." Electrodes implanted in the brain that electrically stimulate specific regions are now being tested as treatments for depression and other mental illnesses; conceivably this technology also could be used to induce mystical states.

Suppose scientists found a way to give us permanent, blissful, mystical self-transcendence. Would we want that power? Before Timothy Leary touted LSD as a route to profound psychological and spiritual insight, the CIA was studying its potential as a brainwashing agent. Persinger warns that in the wrong hands, a truly precise, powerful God machine, capable of implanting beliefs or signals that seem to come straight from the Almighty, could be the ultimate mind-control device. "Just think of the practical impact," he says. "People will die for this."