Neuroscience and Religion: An Overview

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Neuroscience is the study of the nervous system, including the brain, spinal cord, and peripheral systems. As a discipline, it reached maturity only in the twentieth century. Developments in brain-scanning technologies, in particular, have revolutionized neuroscience, and it can only be expected that the existing and growing body of literature will continue to expand. As neuroscience develops, its findings are increasingly seen to have implications for religious worldviews and the study of religion.


Awareness of the nervous system and its role in the human body dates back at least to the Roman physician Galen (third century bce), who understood movement to be controlled by the nerve cords extending through the body. By the end of the eighteenth century, the major anatomical features of the brain were known, as well as the central relationship of mind and brain. This knowledge was most famously reflected in the work of René Descartes (15961650), who understood the motions of the body to be controlled by mechanistic animal spirits originating from the brain, connected to the nonmaterial mind through the pineal gland.

It was not until the mid- to late nineteenth century that neuroscience began to emerge as a separate discipline, thanks to new experimental techniques and the increasing refinement of the microscope. It came to be realized that the central building block of the brain and nervous system was the neuron, a kind of cell that appeared designed to communicate by electrical impulses. In addition, studies in functional neuroanatomy had begun to associate specific forms of brain damage with specific kinds of mental deficits. Paul Broca (18241880), for instance, showed that damage to a region in the left hemisphere of the brain (now known as Broca's area) resulted in the inability to produce speech. Findings of this kind were capitalized on for dubious purposes, most notably the pseudo-science of phrenology, but the work of Broca and his colleagues has since been well substantiated.

Despite these advances, neuroscience did not truly become established until after World War II. This progress was made possible, in part, by the large number of war casualties, who made ideal test subjects for neuroscientists studying the relationship between brain and thought. The period of the 1950s through the 1970s was one of tremendous growth, particularly in the area of functional neuroanatomy and in the understanding of the basic functioning of the neuron. By the 1980s these findings began to come together to make a coherent whole. This process was abetted by the use of computational models for understanding the brain and mind and by the use of new scanning technologies (most notably magnetic resonance imaging, or MRI) that allowed images of living brains and, eventually, imaging of the brain in action, enabling neuroscientists to see what areas of the brain become active during specified tasks.

For most of this history, religion has rarely been the subject of theorizing by neuroscientists, but this is not to say that there were no interactions between neuroscience and religion. Descartes's mechanistic understanding of the brain and body can be understood to fall within the context of a larger, religious worldview. The important discoveries about the nervous system made by Hermann von Helmholtz (18211894)showing, among other things, that it takes time for nerve signals to communicate over distanceswere driven by his materialistic convictions. Furthermore, two of the twentieth century's most famous psychologists of religion, Sigmund Freud and William James, both had significant exposure to the advances in neuroscience in their day. Religious beliefs (or the lack of them) thus played an important background role in shaping the field of neuroscience, while the findings of neuroscience (real or putative) were sometimes used to justify positions about religion.

Current Character of Neuroscience

Knowledge of the brain and how it works grew enormously in the second half of the twentieth century and into the twenty-first, so much so that the U.S. Congress designated the 1990s as the "decade of the brain" to commemorate and further brain research. It is now estimated that the brain is composed of approximately 100 billion nerve cells. In turn, each nerve cell is typically connected to 3,000 to 10,000 other nerve cells, and it has been suggested that there are on the order of 100 trillion such connections. It is important to note the staggering complexity that this implies: that there are more neuron connections than there are stars in the Milky Way Galaxy. Neurons communicate by sending electronic impulses facilitated by chemical reactions that are still not fully understood. Chemicals known as neurotransmitters play an essential role in this communication. Imbalances in neurotransmitter production and uptake play important roles in some forms of mental illness (such as schizophrenia, Parkinson's disease, and depression) and altered states of consciousness (due, for instance, to drug use).

Much of the functional organization of the brain has been mapped out. It is now known that, for most individuals, the majority of language processing occurs in the left hemisphere of the brain. Visual processing occurs in the occipital lobe in the rear, motor control is centered along the midline of the brain, and complex rational thought seems to be concentrated in the frontal and prefrontal cortexes immediately behind the forehead. Emotional responses seem to be controlled by a collection of brain structures known as the limbic system. In many cases the correspondence between a specific behavioral ability and the specific area of the brain responsible for it has been mapped out in considerable detail. When damage to an area of the brain occurs, the corresponding ability is lost, sometimes permanently and sometimes with counterintuitive results. Prosopognosia (the inability to recognize faces) is the result of one such instance of brain damage. People with this condition are unable to tell one face from another, even though they may recognize people by other means (e.g., by the sound of their voice or the clothes that they are wearing).

It has become common among some scientists to compare the mind and brain to a computer. Though this metaphor has proven useful in some ways, it is also exceedingly misleading in others. Individual neurons function somewhat analogously to the individual logic gates of a computer chip, but there is no central processor as is typical on modern desktop computers. A closer analogy has been computers that utilize decentralized parallel distributed processing (PDP) or neural networks, and it has been shown that individual neuronal groups are capable of such processing. However, the analogy between brains and computers has been a contentious one, with some neuroscientists utilizing computational metaphors and others strongly denying any such link.

Among recent areas of development, three may be seen as particularly important. First, a growing body of research has helped to reveal the centrality of emotion in brain processing and cognition. Research by Antonio Damasio (1994) has shown that rational thought and emotion are not completely distinct from one another, and to think rationally one must have a proper repertoire of emotional responses as well. This has contributed to a move away from thinking of the brain as simply a computer-like thinking machine. Second, research in brain development is helping to show how the brain comes to organize itself in relation to its environment. The brain goes through dramatic changes in the early periods of childhood, and there is good evidence that the brain continues to change in subtle ways throughout a person's life. The prefrontal cortex (responsible for reasoning) continues in its development through late adolescence. Increasing knowledge of genetics is also beginning to illuminate the ways in which specific genes influence brain development, suggesting the potential for providing links between assemblies of genes and specific human behaviors. Furthermore, individual neurons have been shown to be exceedingly plastic, changing their receptivity to communication from and to other neurons throughout one's life. Third, some research has indicated the possibility of brain-machine interfaces in the not-so-distant future. Magnetic fields, for instance, can be used to stimulate specific areas of the brain, either for research or therapeutic purposes (to alleviate depression, for instance). Work with rhesus monkeys has shown that a machine interface can be used to control a mechanical device by a thought command alone, suggesting help for individuals with physical disabilities but also raising questions about the relationship of human beings and machines.

Neuroscience, the Mind-Body Relation, and Personhood

There are a number of ways in which neuroscience might be said to relate to or have an impact on religious traditions and religious thinking. The most obvious concerns the relationship of mind to body. Religious beliefs about the nature and relation of the mind and the body have been varied and complex. In the earliest forms of Judaism, Christianity, and Islam, the tendency was to think of persons as wholes, distinguishing between body and spirit but maintaining their essential unity. As a result, these traditions looked forward to a resurrection of the dead that united (or reunited) spirit and body. Later thought, especially in the Christian tradition, was profoundly influenced by Platonism, with the result that emphasis was placed on the survival of an immortal soul separate from the body. This distinction was accentuated by later Christian philosophers and theologians, most notably Réne Descartes. Other religious traditions have subscribed to quite variant understandings of the human person and mind-body relationship. Hinduism speaks of the ātman, or self, but sometimes in quite different ways than the monotheistic traditions (as is most obviously reflected in the Upanishads and the Advaita Vedanta tradition). Buddhism has historically subscribed to a doctrine of anātman, or no-self, and so has traditionally denied the existence of a soul in any straightforward sense.

As a science, neuroscience does not address the broader question of mind and body, although its findings can be said to have consequences for particular religious views. Neuroscience does seem to rule out any straightforward account of mind-body dualism. Damage to the brain leads to loss of cognitive function, often in fairly predictable ways. Such potential damage is not limited to motor functions, but can also affect higher-order thinking and emotional response. Brain damage or alteration of brain chemistry can lead sometimes to rather profound alterations of personality. It should be noted that this damage affects not simply the behavior of the individual but one's subjective experience as well. Someone who suffers a stroke and is afflicted with temporary aphasia (the inability to speak) because of brain damage is not simply prevented from speaking the words. When recovered, they will testify they were unable to even think of the words (or think in words) while having the disability. With a few, early, and prominent exceptions (most notably Wilder Penfield and John Eccles, two of the more famous neuroscientists of the twentieth century), few neuroscientists now count themselves dualists, and most would argue that mind and body are intimately linked.

It is important to note, however, that neuroscientists remain perplexed by the phenomenon of consciousness. Beginning in the late 1980s, neuroscientists began to consider consciousness as a legitimate subject of inquiry. Most efforts at explanation have been devoted to the function of consciousness rather than its very nature. Philosopher David Chalmers (1997) has usefully distinguished between the "easy problems" of consciousness and the "hard problem." The easy problems deals with cognitive functions associated with consciousness (such as attention, bodily representation, and the ability to think about one's thoughts and so be self-conscious), but they do not tell us why there is a subjective quality to consciousness at all. This latter question, to date, remains better suited to philosophy than science, and it may be permanently so.

Beyond the mind-body relationship, neuroscience may be seen to have repercussions for more general understandings of personhood. Research into the physical factors linked to specific behaviors and personality, particularly when tied to advances in developmental biology and behavioral genetics, stand to have fairly profound implications for doctrines of free will and the meaning and nature of personal transformation. The advent of subtle, personality-altering drugs such as Prozac and the increasing trend toward diagnosing and using drugs to treat personality variants such as attention deficit disorder (ADD) reveals the complex relationship of person, biology, and environment in ways that have implications for religious doctrines of health and happiness. Such implications have, to date, led to little in the way of religious reflection, but will become increasingly important in the coming decades.

Neuroscience and Religious Experience

A recent area of neuroscientific exploration has been the nature of religious experience itself and its possible roots in the brain. There has been a long tradition of scientific speculation on the nature of religious experience. For much of its history, when neuroscience has on rare occasion turned its attention to the topic of religious experience, the tendency has been to associate it with one or another form of mental illness. William James, for instance, chided medical materialists (as he called them) for attempting to reduce religious experience to mental illness. One early favorite candidate has been temporal lobe epilepsy, which has been known to produce in some individuals profound religious experiences prior to the onset of seizures. The Russian novelist Fyodor Dostoevsky is probably the most famous example of this phenomenon. Knowledge of such instances has been used by some neuroscientists (Robert Persinger in 1987, for example) as a general explanation for religious experience. Research by V. S. Ramachandran (Ramachandran and Blakeslee, 1998) has shown this to be unlikely, however, as religious individuals with no epilepsy seem to respond differently in tests using religious imagery than individuals with temporal lobe epilepsy.

Beginning in the 1990s, some neuroscientists turned their attention to Buddhist meditation as a subject of research. Meditation has proven to be a congenial subject of research because it is largely stationary, predictable, and has a base of willing test subjects. The primary concern of this research has been to link meditational states with heightened or lowered activity in specific regions of the brain. Research done by Eugene D'Aquili and Andrew Newberg (1999) has shown that such meditation consistently correlates with heightened activity in some areas of the brain (the prefrontal cortex, for instance) and lowered activity in others (most specifically areas in the parietal lobes associated with spatial orientation). D'Aquili and Newberg theorize that it is the alteration of these brain states that leads to the particular experiences (e.g., a sense of unity and a loss of distinction between self and other) that meditation is traditionally said to give rise to.

There are deep divides as to how to interpret such research. Some argue that studies that correlate brain states with religious experiences show that these religious experiences are not real, i.e., religious experiences are nothing but a form of brain dysfunction or even mental illness with no basis in any kind of higher reality. On this account, religious experience is necessarily illusory in character, and such research can be taken as evidence for a more general reductive account of religion. D'Aquili and Newberg, however, have argued that their research shows that religious experience is part of the normal functioning of the brain and should not be characterized as a form of mental illness, as has often been the case in psychology. They also argue that the implications of such research are not reductive. Rather, they claim, it should be admitted that the realities such brain states reveal are just as real as those of ordinary experience, and so one should not be privileged over the other.

Some important limitations of these studies should be noted. To date, the studies done have been small, involving few subjects, thus raising the probability of error or variant results in further trials. In addition, it is important to note that meditational practices vary from tradition to tradition, and what holds true for one form of meditational practice may not hold true for all. Furthermore, it would be a mistake to suppose that religious experiences arising from meditation can simply and straightforwardly be used as a model for explaining all religious experiences. Religious experience is diverse and complex, and there are likely multiple factors involved.

Neuroscience, Uniqueness, and Dignity

Issues of uniqueness and human dignity may also be raised by neuroscience and its related fields. Evidence reveals that human beings evolved from ape-like ancestors approximately six million years ago. There is now a significant amount of fossil data with which to construct key aspects of this evolutionary history, although the details remain contentious and ongoing discoveries have revealed the complexity of the evolutionary links. The evidence does show, however, a gradual rise in cranial size from very old fossils like Australopithecus afarensis (about five million years ago with brain size equivalent to that of a modern chimpanzee) to Homo erectus to Homo sapiens. Because the brains themselves are not preserved, brain development can only be inferred from the size and shape of the brain case and other physiological clues. One important issue has been determining when the brain reached its current state of development, with some suggesting that changes were still taking place as recently as 40,000 years ago (about the time that we see some of the first cave art).

Greater understanding of the minds and brains of other animals may also provoke religious reflection. Research with dolphins and apes (particularly chimpanzees and bonobos) in particular has shown sometimes surprising intellectual abilities. A dolphin brain is about the size of a human brain, although its different organization suggests that it would be a mistake to assume this to mean equivalent intellectual ability. Although their brains are smaller than ours, chimpanzees are capable of some symbolic communication and are capable of recognizing themselves in a mirror (an ability comparatively rare among animals), which has been taken to suggest some level of self-consciousness. Moreover, genetic studies indicate that chimpanzees share up to 98 percent or more of their genes with human beings.

The extent to which these findings will be important for religious belief will clearly vary from tradition to tradition. Monotheistic traditions have been much more inclined to insist on an absolute division between human beings and animals than, for instance, Hinduism and Buddhism. Distinctions are observed, however, even in these latter traditions. From a neuroscientific perspective, any claim of an absolute divide between human beings and animals would be difficult to support, especially when evolutionary histories are taken into account. Rather, it seems much more likely that a continuum exists, albeit one with important leaps along the way.


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Gregory R. Peterson (2005)