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Psychologists and neuroscientists have begun to uncover the biological mechanisms that might give rise to feelings of revelation in healthy adults. Noelle discusses some of these scientific findings, focusing on circuitry, modularity, and innateness.

I have certain, positive knowledge from my own direct experience. I can't put it any plainer than that. I have seen God face to face." With these words, the fictional theologian Palmer Joss defends his religious convictions in Carl Sagan's 1985 novel, Contact. Joss argues for the existence of his Christian god on the basis of personal revelation. And Joss is not alone. Many religionists rest their faith on the apparently solid foundation of personal religious experiences. Some receive visions. Others hear a comforting voice. Almost all experience a "sense of presence" or a feeling of "unity with the universe." Such episodes typically bring catharsis, joy, and calm. Importantly, these experiences are not reported solely by people suffering from brain damage or mental illness.

We may, quite rightly, reject such subjective experiences as lacking the necessary qualities of scientific evidence, such as reproducibility and openness to consensual validation or critique. The religionist may retort, however, that his belief may not be scientifically justifiable, but he knows it to be true, nonetheless, because of his private religious revelation.

To completely counter this argument for the existence of god(s), some alternative explanation must be given for the religious experience. Researchers in the fields of psychology and neuroscience have begun to uncover the biological mechanisms that might give rise to feelings of revelation in healthy adults. I will briefly review and critically assess some of these scientific findings, focusing specifically on three questions:

1. Circuitry-What brain circuits are involved in religious experiences?

2. Modularity-Does the brain contain a special module dedicated to religious experience?

3. Innateness -Is there a "religion instinct" that is genetically "hardwired" into our brains?

THE 'GOD MODULE' DISCOVERY

In October 1997, a presentation boldly titled "The Neural Basis of Religious Experience" was given at the annual conference of the Society for Neuroscience by neuropsychologist Dr. V. S. Ramachandran and his colleagues. The Los Angeles Times reported that, "researchers at the UCSan Diego brain and perception laboratory determined that the parts of the brain's temporal lobe-which the scientists quickly dubbed the `God module'-may affect how intensely a person responds to religious beliefs." The story suggested that there were now at least partial scientific answers to all three of our questions concerning religious experience. The circuits underlying religious experience are in the temporal lobe of the brain; they form a distinct religion module that is substantially innate. Experimental results were "leading the scientists to suggest a portion of the brain is naturally attuned to ideas about a supreme being."

One common way to hunt for a module in the brain is to examine patients with various kinds of brain damage, hoping to find a localized form of damage that correlates with changes in the behaviors of interest. In this way, one may discover relationships between certain circuits in the brain and certain behavioral functions.

This was the strategy taken by the scientists in San Diego. They decided to focus on temporal lobe epilepsy (TLE) patients, who exhibit inter-ictal behavior syndrome (IBS). These patients are prone to excessive activity in their temporal lobes, causing seizures during which they report powerful religious experiences. Importantly, clinicians have previously reported that such TLE patients are also often fanatically religious, even during the long periods between seizures.

The question asked by Ramachandran and his colleagues was, Why do such seizures often lead to enhanced religiosity? They entertained three possibilities:

1. Strange sensory experiences that arise during seizure are rationally interpreted as signs of paranormal powers.

2. The strong and widespread electrical activity that defines seizures strengthens connections between temporal lobe sensory areas and the amygdala (a brain area associated with emotion). This causes patients to see "deep cosmic significance" in everything.

3. There is a system in the temporal lobe devoted to mediating emotional responses of a religious nature. Seizures can selectively strengthen the connections in this system.

The researchers dismissed the first option on the grounds that other kinds of neurological and psychiatric disorders result in strange hallucinations without causing the development of specifically religious propensities. To distinguish between the remaining two options, the scientists tested TLE-IBS patients to see if they had stronger emotional responses to everything in the world or only to religious stimuli. The degree of emotional response was measured through a physiological correlate, skin conductance response (SCR). By measuring small rapid changes in perspiration, the researchers hoped to show that TLE-IBS patients were particularly aroused by religion.

Indeed, that was exactly what was found. The TLE-IBS patients showed preferential emotional arousal when presented with religious words as opposed to words with sexual or violent connotations. Unlike the patients, age-matched healthy control subjects responded most strongly to the sexual words.

While these results seem to indicate that there is something distinctly religious about some of the circuitry in the temporal lobes, there are some reasons to be cautious about this conclusion. First, this study involved only three patients, and the preference for religious words was not equally robust in all three. Also, TLE-IBS patients sometimes exhibit changes in sexuality, becoming obsessed with the topic or bored by it. This symptom could have impacted the patients' responses to the sexual stimuli. In short, these results should be seen as preliminary.

In the end, this experiment suggests only that TLE-IBS patients do, indeed, display religion-specific symptoms. This, in turn, suggests that the brain's temporal lobe is involved in religious experience. The degree to which religion is a distinct or genetically determined part of our neural architecture has yet to be determined.

TUNING INTO THE DIVINE

In the film Raiders of the Lost Ark, a large metal religious artifact called the "Ark of the Covenant" is described as "a radio for speaking to God." While, to date, no one has produced such a radio that can tune into the divine, one neuroscientist has fabricated something similar. Dr. Michael Persinger of Laurentian University has devised a machine that generates a particular kind of magnetic field around the head, producing "micro-seizures" in the temporal lobes of the brain. Healthy people who have experienced this induced brain activity have reported such things as a feeling of floating, deformations of the body, strong emotions, a "sensed presence," and specifically religious dreamlike hallucinations.

Persinger's experimental work arose after years of research into the neurological basis of religious experiences. Over this time, he has constructed and refined a rather detailed account of the neural processes that may underlay feelings of supernatural contact.1 In brief, religious experiences are seen as the result of "temporal lobe transients" (TLT)-short-lived rate increases and instability in the firing patterns of neurons in the temporal lobe. These transients are seen as miniature versions of the seizures experienced by temporal lobe epileptics, and they are thought to occasionally arise in healthy people.

Persinger has speculated as to why such TLT events would produce the particular configuration of experiences reported as religious revelations. He sees a critical part of our "sense of self" as being maintained by systems in the left hemisphere temporal cortex. Most of the time, there is "matched" activity in the analogous places in the right hemisphere. However, when activity on the right gets out of sync with activity on the left, as during a TLT event, the left hemisphere interprets the mismatched activity as "another self" or a "sensed presence'-the mind of God. In conjunction with this experience comes excessive stimulation of subcortical areas in the temporal lobe, particularly the amygdala (associated with emotion) and the hippocampus (associated with autobiographical memory). Excitation of these areas results in the attribution of personal meaning to the experience. These powerful TLT events may naturally result from a number of factors, including increased sensitivity or lability of right temporal areas, loss of oxygen to the brain, and changes in blood sugar. These biological conditions may be caused by crisis situations, prolonged anxiety, near-death contingencies, high altitudes, starvation and fasting, diurnal shifts, and other physiological stressors.

A variety of correlational studies on healthy adults have been conducted by scientists in Persinger's lab. Assuming that people who are prone to TLT events will show subtle signs of a tendency towards hemispheric mismatch even when not experiencing a "microseizure," Persinger and his colleagues have examined the "brain waves" of a large number of healthy subjects and have compared these results with reports of religious experiences. They have found that a particular low-frequency component of one's electroencephalogram (EEG) trace, known as the theta rhythm, can partially predict the likelihood of having religious experiences.2 Across healthy subjects, hemispheric mismatch in the theta component correlates with reports of previous "sensed presence" experiences. Furthermore, signs of specifically subcortical (limbic) mismatch in the temporal lobes are correlated with belief in paranormal phenomena, whereas indications of mismatch in the cortex are correlated with previous "sensed presence" experiences.3 In short, there is good correlational evidence that one's tendency to have religious experiences involves interhemispheric circuits in the temporal lobe.

While these results are interesting, Persinger's work involving the actual generation of religious experiences is

much more striking. In a typical experiment, the subject is isolated from sounds and the eyes are covered. A helmet equipped with solenoids is strapped to the head. While reclining in this state of partial sensory deprivation, currents are induced in the subject's brain through the generation of patterned extremely low frequency milligauss magnetic fields in the solenoids. The subject is asked to describe any experiences aloud, and this monologue is recorded.

By manipulating the magnetic field, the experimenter has some control over the location and pattern of induced current in the brain. When subcortical (limbic) areas in the temporal lobes are targeted, subjects often report distortions in their body images, senses of forced motion, and strong emotional reactions. For example, Dr. Susan Blackmore entered Persinger's experimental chamber and reported a sense of swaying motion, a feeling of being yanked into an upright position, a sense that her leg had been stretched halfway to the ceiling, a period of intense anger, and a flash of terror.4 When temporal cortical areas are targeted for stimulations, subjects often report dreamlike visions (often with mystical or religious content), a "sense of presence," and strong emotions. Journalist Ian Cotton, for example, reported highly detailed visions of his childhood home, a dreamlike visit to the monks of a Tibetan temple, and an emotional "realization" that he too was, and always had been, a Tibetan monk.5 Visions are particularly sensitive to suggestion, with the content being influenced by, say, the presence of a crucifix or the playing of distinctly Eastern music.

With these experimental results in mind, our three questions might be asked of both Persinger's theory and of his data. Persinger holds that subcortical temporal lobe systems contribute to paranormal experiences and paranormal belief. Cortical areas in the temporal lobes participate in the "sense of self" and, during periods of hemispheric mismatch, in the "sensed presence." His correlational and experimental data both support the notion that temporal circuits are central to religious experience. With regard to the question of modularity, Persinger's theory specifically denies the existence of a distinct "God module." In his view, the brain areas responsible for religious experience are exactly those areas that also mediate "sense of self," general emotional responses, and autobiographical memory. While his experimental work does not bear on this question, his correlational data support this distributed view. The likelihood of having religious experiences is systematically related to these other properties of cognition.

Persinger's position on the question of innateness is more ambiguous. In his writings, he frequently points out that religious experiences can have positive effects. He sees TLT events as a remedy for extreme anxiety.6

The God Experience has had survival value. It has allowed the human species to live through famine, pestilence, and untold horrors. When temporal lobe transients occurred, men and women who might have sunk into a schizophrenic stupor continued to build, plan, and hope.

While such "survival value" facilitates the incorporation of a feature into the genome, the utility of a behavior is not enough to ensure such fixation in DNA. For example, the making of bread is a skill with great survival value, but it is unlikely that this skill is genetically encoded. Still, Persinger seems to lean towards a largely nativist account. Unfortunately, the data that has emerged from Persinger's lab does not really address the question of innateness.

Note that, even if a tendency towards experiencing TLT events was found to be influenced by one's genes, this would not necessarily mean that religious experiences have been favored by natural selection. For example, it might be the case that temporal lobe lability contributes to imagination and creativity, and this lability also accidentally results in religious experiences. In short, the question of a "religion instinct" is far from settled by Persinger's work.

Persinger's investigations have yet to fully confirm his views on the neurological bases of religious experience, but he has made tremendous progress. Unlike Ramachandran's work with TLE-IBS patients, Persinger has focused on healthy adults. He has shown that particular activity patterns in the temporal lobes of healthy brains can give rise to experiences that are very similar to the spontaneous religious experiences reported by many.

ANSWERING REVELATIONS

Modern science is beginning to understand the neurological mechanisms that give rise to the religious experiences of the believer. Given these results, the skeptic may present the believer with a simple question: How do you know that your religious experience is not a simple trick of your brain-the unfolding of a perfectly natural temporal lobe transient? How can you trust such an experience when, through science, we can convincingly mimic the face of God?