New Scientist Belief Special
28 January 2006
|"Glad to be Gullible" | "How evolution found God" | "When delusion triumphs over truth" |
Glad to be gullible
It is five minutes past midnight and I am alone in my house. I am working late, and the only illumination is the blue-white glow from my laptop computer. I live in a quiet London suburb, and at this time of night distractions are confined to the occasional eerie screeches and hisses from marauding urban foxes.
I pick up the phone to call Michael Thalbourne, a psychologist at the University of Adelaide in Australia. I want to talk to him about his research on chance, coincidence and the paranormal. Although the interview time has not been prearranged, we have been in contact by email, so it is disconcerting to hear a long pause when I introduce myself. When Thalbourne eventually speaks he sounds taken aback. "I was right in the middle of typing out an email to you," he says.
Thalbourne's instinct is to suspect some paranormal explanation for our synchronicity. My gut reaction is to suggest a more mundane alternative. It looks as if he is what some psychologists would call a sheep, while I am a goat.
The animal terminology stems from a passage in the Bible about a shepherd sorting through his flock to separate the sheep - representing the nations that believe in God - from the goats, or those that do not. Thalbourne and his ilk, however, are interested in belief in the paranormal and supernatural. And such beliefs turn out to be surprisingly common. For example, a 1998 survey of 1000 adults in the UK showed that one-third believed in fortune telling, half believed in telepathy, and a whopping two-thirds agreed with the statement that some people have powers that science cannot explain.
Decades of scientific research into parapsychology have produced no convincing demonstration of the paranormal that can be reliably reproduced - the acid test of scientific inquiry. So why should scientists be so interested in whether or not people believe in it? Research into the differences between sheep and goats has over the years produced some intriguing findings about how the brain works.
Until recently, sheep might have been forgiven for being cheesed off by all this research - most of the findings were less than complimentary about them. Study after study suggested that sheep saw paranormal events where there were none, simply because they were worse at judging probabilities and randomness, and even at using logical reasoning. But newer research might restore some sheepish pride. It turns out that the kind of thinking involved in belief in the paranormal helps us carry out a range of important cognitive tasks, from spotting predators to recognising familiar faces. Sheep also tend to be more imaginative and more creative. Some psychologists even think that people who believe they have paranormal powers such as telepathy, dreams that foretell the future, or other forms of extrasensory perception (ESP) might actually be accessing information stored in their subconscious without realising it.
Imagine, for example, that you are walking along the street with your old friend Bob, when you start thinking about a mutual college chum, Joe. "I wonder what Joe Smith is getting up to these days," you say. "That's amazing!" says Bob. "I was just thinking of Joe myself." You believe it is simply a coincidence. Bob suspects some form of telepathy. But there is a third explanation: without being consciously aware of it, both you and Bob noticed something that reminded you of Joe. Maybe you passed someone who looked just a little bit like him, or maybe it was something in a shop window that reminded you of him.
It was Thalbourne who first suggested that people who regularly have subconscious information such as this surfacing in their conscious mind would often seem to require the paranormal to explain their experiences. He coined the term "transliminality" for this tendency for information to pass between our subconscious and our conscious mind. He has also designed a questionnaire to measure transliminality. It asks questions such as how good people are at using their imagination, whether they have a heightened awareness of sights and sound and whether they have ever felt they have received "special wisdom". Thalbourne and others have shown in several studies that transliminality corresponds to where people fall on a sheep-goat scale. In other words, the better you are at tuning in to your subconscious, the more likely you are to believe in the paranormal.
This correlation alone suggests Thalbourne may be onto something. And in 2002, a group at Goldsmiths College in London reported an intriguing practical demonstration of transliminality (Perception, vol 31, p 887). They asked people to take part in an apparent test of ESP with Zener cards, which display one of five symbols: a circle, a cross, a square, a star or three wavy lines. The subjects sat in front of a computer monitor displaying the back of a card. They pressed a key to choose which symbol they thought it was. Then they got to see the card's face.
What they did not know was that they were being given subliminal clues as to which symbol was about to appear. Before a card's back was shown, they saw a flash of its face lasting for just 14.3 milliseconds, too fast for most people to register. Some participants, however, were able to subconsciously pick up on the clue, and as a result they scored better than chance at predicting which symbol would appear. "To those participants it would appear that they had ESP abilities," says psychologist Chris French, who led the research. And people who were best at picking up the subliminal image also turned out to be the most transliminal as measured by Thalbourne's questionnaire. It was a neat demonstration of how access to subconscious information can give the appearance of psychic abilities.
The talents of people who believe in the paranormal don't end there. It seems that they are also better than non-believers at perceiving meaningful patterns in apparently random noise. The classic example of this trait, which is known as pareidolia, is when people claim to see images of the Virgin Mary, say, on the wall of a building or a tortilla. Pareidolia can be auditory as well as visual, as shown by the current craze for detecting electronic voice phenomena (EVP), supposed messages from the dead buried in the random noise of audio recordings.
Psychologists have traditionally viewed this quality as a shortcoming on the part of sheep. But Peter Brugger, a neuroscientist at the University Hospital Zurich in Switzerland, does not think it is a black-and-white issue. He explains that people commit what statisticians call a type 1 error when they perceive a pattern where none exists - when they are overly gullible, in other words. A type 2 error is when they fail to recognise a pattern that does exist - when they are too sceptical. Brugger points out that pattern recognition is an important aspect of human cognition, allowing us to recognise familiar faces or camouflaged predators. "From an evolutionary perspective, the price for protection against type 2 errors is a susceptibility to type 1 errors," Brugger says. He theorises that it may be safest to err on the side of gullibility. "If you miss the tiger hidden in the grass, then you are dead. If you always see tigers, you are always running away but you're not dead."
What determines our tendency to spot patterns and form associations? It turns out that a key factor is the relative dominance of the right and left hemispheres of the brain. There has been much dubious pop psychology written about the differences between "right-brain people" and "left-brain people". But most neuroscientists would accept that the left side of the brain is primarily responsible for language and logical analysis, while the right side is more involved in creativity and what might be called lateral thinking - making connections between disparate concepts.
Several recent studies using various techniques suggest that people who believe in the paranormal have greater right-brain dominance. In 2000 Brugger's group showed, for example, that believers have greater electrical activity in the right hemisphere than non-believers as measured by electroencephalogram (EEG) recordings (Psychiatry Research: Neuroimaging, vol 100, p 139). In a different approach, in 2001 they asked people to carry out word-association tasks using different sides of their brain by looking at the words with just one eye at a time. When using their right brains, the sheep among them were faster than the goats at finding connections between distantly related words such as "lion" and "stripe" (the connection is "tiger") (Psychopathology, vol 34, p 75). In some cases, says Brugger, "the disbelievers didn't even note that there was a relationship".
But when taken to extremes, there can be a less welcome side to right-brain thinking. Brugger and others have shown that there is also relatively more right-brain activity in people with schizophrenia, particularly in those whose symptoms involve delusional beliefs. Brugger says this aspect of his research has not gone down well with the paranormal community. "I'm a very disliked person," he admits.
Of course neither Brugger nor anyone else is saying that people who believe in the paranormal are schizophrenic. But while an enhanced ability to spot real patterns and form connections is desirable, it could be argued that believers in the paranormal have taken this tendency too far. Then again, that depends on whether you are a sheep or a goat.
As a goat myself, I tend to opt for down-to-earth explanations. Here, for example, is how I account for the fact that Thalbourne was emailing me just as I phoned for that interview. Earlier that day, while it was already night-time in Adelaide, I had sent him an email asking if we could arrange a time to talk. Later I decided to chance a phone call anyway, and not wanting to stay up working any longer than necessary, I called at midnight my time, or 8.30 am in Adelaide, which I figured was probably the earliest he would arrive at his office. He had actually got to work shortly before, and started his day as many of us do by turning on his computer and was responding to the emails he received overnight - which happened to include one from me. QED.
Thalbourne, however, persists in viewing the event as one of life's intriguing little coincidences. But then he does happily admit to being a sheep. "My life is full of many small and occasionally large coincidences that suggest some unusual form of cause and effect," he says. "I believe that I can't disbelieve in it."
How evolution found God
Do they know what God's thinking?
Religious belief is a conundrum. In our everyday lives, most of us make at least some effort to check the truth of claims for ourselves. Yet when it comes to religion, studies show that we are most persuaded by stories that contradict the known laws of physics. Tales of supernatural beings walking on water, raising the dead, passing through walls, foretelling the future, and the like, are universally popular. At the same time, however, we expect our gods to have normal human feelings and emotions. We like our miracles, and those who perform them, to have just the right mix of otherworldliness and everyday characteristics.
Why are we humans so willing to commit to religious beliefs we can never hope to verify? You might well think that question falls outside the realm of scientific investigation. Evolutionary biologists in particular have taken their cue from their own guru, Charles Darwin, and studiously ignored the whole issue of god. But now that is starting to change. It's not clear what has triggered the interest, but a significant factor has probably been the growing recognition that religion is a real evolutionary puzzle. On the face of it, religious behaviour seems to be at odds with everything we biologists hold dear. The reductionist view sees us as merely vehicles for our selfish genes - yet religions embrace charity to strangers, submission to the will of the community, and even martyrdom. No self-respecting baboon or chimpanzee would ever willingly kowtow to the good, the bad or the ugly in quite the same way humans do.
Perhaps the biggest stumbling block for evolutionary biologists has been recognising that religion might have a functional advantage. If a biological trait has evolved, we want to know what use it is - and by that we mean how does possessing this trait make an individual better adapted to survive and pass their genes on to the next generation. That's not always apparent where religion is concerned. But in recent years, evolutionary biologists including myself have come to realise that there are some important aspects of religion that do seem to have benefits.
Evolutionary biologists have identified at least four ways in which religion might be of benefit in terms of evolutionary fitness. The first is to give sufficient explanatory structure to the universe to allow us to control it, perhaps through the intercession of a spirit world. The second is to make us feel better about life, or at least resigned to its worst vagaries - Marx's "opium of the masses". A third is that religions provide and enforce some kind of moral code, so keeping social order. Finally, religious belief might bring a sense of communality, of group membership.
The first idea - religion as cosmic controller - seems highly plausible, given that many religious practices aim to cure diseases and foretell or influence the future. It was the view favoured by Freud. However, since religious belief does not necessarily enable us to control the vagaries of the world, I find it difficult to see this as the evolutionary force behind the origin of religion. Rather, I suspect that this benefit came about as a by-product once our ancestors had evolved religion for one of the other reasons - and thus had a big enough brain to figure out some metaphysical theories about the world.
The second hypothesis, Marx's opium, seems more promising. In fact, it turns out that religion really does make you feel better. Recent sociological studies have shown that compared with non-religious people, the actively religious are happier, live longer, suffer fewer physical and mental illnesses, and recover faster from medical interventions such as surgery. All this is bad news for those of us who are not religious, but it might at least prompt us to ask why and how religion imparts its feel-good factor. And we'll come back to that later.
The other two options are concerned with individuals benefiting from being part of a cohesive, supportive group. Moral codes play an obvious role in ensuring that group members keep singing from the same hymn sheet. Nevertheless, the sort of formalised moral codes preached and enforced by today's major religions are unlikely to provide much insight into the beginnings of religious belief. They are associated with the rise of the so-called world religions with their bureaucratic structures and the alliance between church and state. Most people who study religion believe that the earliest religions were more like the shamanic religions found in traditional small-scale societies. These are quite individualistic, even though some individuals - shamans, medicine men, wise women, and the like - are acknowledged as having special powers. Shamanic religions are religions of emotion not intellect, with the emphasis on religious experience rather than the imposition of codes of behaviour.
In my view, the real benefits of religion in terms of evolutionary fitness have to do with the fourth hypothesis. The idea that religion acts as a kind of glue that holds society together was also favoured by Emil Durkheim, one of the founding fathers of modern sociology. Now, though, we know more about how this works. Religions bond societies because they exploit a whole suite of rituals that are extremely good at triggering the release of endorphins, natural opioids in the brain. Endorphins are part of the body's pain-control system, a slow-acting mechanism that takes over when the various neurological systems of pain control have peaked in their effectiveness. Endorphins come into their own when pain is modest but persistent - then they flood the brain, creating a mild "high". Perhaps that is why religious people often seem so happy. What's more, and here's the rub, endorphins also "tune up" the immune system, which probably explains why religious people are healthier.
This may be why religious rituals so often involve activities that are physically stressful - singing, dancing, repetitive swaying or bobbing movements, awkward postures like kneeling or the lotus position, counting beads, and occasionally even seriously painful activities like self-flagellation. Of course, religion is not the only way to get an endorphin fix. You will also get a high from jogging, swimming or pumping iron, but religion offers something more. When you experience an endorphin rush as part of a group, its effect is ratcheted up massively. In particular, it makes you feel very positive towards other group members. It creates a sense of brotherhood and communality.
While this may explain the immediate advantage of religion, it raises the question of why we need it at all. The answer, I believe, goes back to the very nature of primate sociality. Monkeys and apes live in an intensely social world in which group-level benefits are achieved through cooperation. In effect, primate social groups, unlike those of almost all other species, are built on implicit social contracts: individuals are obliged to accept that they must forgo some of their more immediate personal demands in the interests of keeping the group together. If you push your personal demands too far, you end up driving everyone else away, and so lose the benefits that the group provides in terms of protection against predators, defence of resources and so on.
The real problem that all such social contract systems face is the "free-rider" - someone who takes the benefits of sociality without paying their share of the costs. Primates need a powerful mechanism to counteract the natural tendency for individuals to free-ride whenever they are given the chance. Monkeys and apes do this through social grooming, an activity that creates trust, which in turn provides the basis for coalitions. Exactly how this works is not yet clear, but what we do know is that endorphins are a vital ingredient. Grooming and being groomed lead to the release of endorphins. Endorphins make individuals feel good, providing an immediate motivation to engage in the activity that bonds the group.
The trouble with grooming as far as our own species is concerned, however, is that it is a one-on-one activity, so it's very time-consuming. At some stage in our evolutionary past, our ancestors began living in groups that were too large for social grooming to provide effective glue. Such large groups would also have been especially prone to exploitation by free-riders. They needed to come up with an alternative method of group bonding. In the past, I have suggested that gossip would have played a role, allowing individuals to perform an activity that provides a similar function to grooming but in small groups rather than one to one. But religion would have taken this a step further, allowing larger groups to bond.
It is important to emphasise, however, that if this account of the origins of religion is right, then it began very much as a small scale phenomenon. Perhaps early religious practices included something like the trance dances found in shamanistic-type religions today. The !Kung San of southern Africa, for example, seek to heal rifts in personal relationships within the community by using music and repetitive dance movement to trigger trances. It is easy to see how this sort of activity could have been beneficial to our ancestors, uniting the group, discouraging free-riders, and so increasing the chances that individuals would survive and reproduce.
However, there is one last issue. Religion is not just about ritual, it also has an important cognitive component - its theology. The endorphin-based group-bonding effects of the rituals only work if everyone does them together. Which is where the theology comes in - it provides the stick and the carrot that make us all turn up regularly. But to create a theology our ancestors needed to evolve cognitive abilities that far exceed those found in any other animal species (see "The origins of religion"). It is these psychological mechanisms that have been exploited down the ages by political elites in various attempts to subjugate the rest of the community. Marx, it seems, was right after all.
The origins of religion
Our ancestors did not always have religion, yet many religious practices seem to have very ancient origins. So when did religion first evolve? Archaeologists have long been fascinated by this question. One indication is burial. Some experts believe this began as far back as 200,000 years ago with the Neanderthals, but the motivation for such cacheing of bodies is ambiguous. So most archaeologists more cautiously define the appearance of religion by looking for evidence of grave goods in burials, since these at least unequivocally imply belief in an afterlife. Deliberate burials of this kind do not occur much before 25,000 years ago. Such burials imply a sophisticated theology, so we can safely assume that these were preceded by a long phase of less sophisticated religious belief. But without evidence on the ground, can we see any further back than this?
I have suggested that there is another way to get an unexpected insight into the question. It comes from asking what kind of mind is required to hold religious beliefs. Take the statement: "I believe that god wants..." To grasp this an individual needs theory of mind - the capacity to understand that another individual (in this case, god) has a mind of his own. Philosophers call this "second-order intentionality" because such statements contain two notions of intent: I believe and god wants. But we need more than this to build a religion.
Third-order intentionality allows me to state: I believe that god wants us to act with righteous intent. At this level, I have personal religion. But if I am to persuade you to join me in this view, I have to add your mind state: I want you to believe that god wants us to act righteously. That's fourth-order intentionality, and it gives us social religion. Even now, you can accept the truth of my statement and still it commits you to nothing. But add a fifth level (I want you to know that we both believe that god wants us to act righteously) and now, if you accept the validity of my claim, you also implicitly accept that you believe it too. Now we have what I call communal religion: together, we can invoke a spiritual force that obliges, perhaps even forces, us to behave in a certain way.
So, communal religion requires fifth-order intentionality, and this also happens to be the limit of most people's capacity as indicated by research done by myself and my colleagues. I think this is no coincidence. The majority of human activities can probably be dealt with using second or third-order intentionality. The two extra layers beyond this undoubtedly come at some considerable neural expense. Since evolution is frugal, there must be some good reason why we have them. The only plausible answer, so far as I can see, is religion. And that's where this line of reasoning can throw light on the origins of religious belief.
As far as we know, all other animals are locked into first-order intentionality, with the exception of great apes who are just about able to cope with second order. If you look at the brains of humans and other animals you find that the level of intentionality they can achieve scales linearly with the volume of grey matter in their frontal lobes (a particularly important part of the brain's processing units). This can be used to work out the level of intentionality our extinct ancestors were capable of - provided you have a fossil skull from which you can measure the overall volume of the brain.
Plotting these values onto a graph, the evidence suggests that as early as 2 million years ago, Homo erectus would have aspired to third-order intentionality, perhaps allowing them to have personal beliefs about the world. Fourth-order intentionality - equating to social religion - appeared with archaic humans around 500,000 years ago. And fifth order didn't appear much before the evolution of anatomically modern humans around 200,000 years ago - early enough to ensure that all living humans share this trait, but late enough to suggest that it was probably a unique adaptation.
In a separate strand of research, my colleagues and I have also found a relationship between the size of the brain's neocortex and social group size in primates. Interestingly, this "social brain hypothesis" predicts that around the time our ancestors evolved the capacity for fifth-order intentionality their community sizes would have exceeded about 120 individuals. Religion may have evolved to provide the mechanism for bonding them into a coherent social unit.
When delusion triumphs over truth
Belief has never literally moved a mountain, but it can have some dramatic effects. Take Madeleine Rizan. By the time she bathed in the waters of Lourdes in 1858 she had been paralysed for 24 years, yet, according to the record, she regained her ability to move. Then there are the dozens of heart patients in the 1950s who were helped by a procedure known as internal mammary ligation - which worked just as well when patients simply believed it had been done. There are even instances of women who stop menstruating, grow a round belly and begin to lactate, in the firm but mistaken belief that they are pregnant. Equally mysterious are the paralysed people who believe their limbs are still working normally, despite the evidence of their own eyes.
What is going on inside our brains when we believe? How does that trigger physical changes in our bodies? And why would our minds believe the world is a certain way in flat contradiction to the evidence of our own senses? Or, put another way, what exactly is the biological basis of belief? "It's a fascinating question and poorly studied," says Vilayanur Ramachandran, a neurologist at the University of California at San Diego who has spent much of his career studying "disorders of belief". Dean Hamer, from the US National Institutes of Health in Bethesda, Maryland, and author of The God Gene, goes further. "We have absolutely no idea," he says. "Nobody has any idea."
In brighter moments, even Hamer would admit the picture is not quite as grim as that. There seem to be at least two lines of thinking on the matter. One is that belief in the widest sense is primarily a product of rationality and reasoning. In order to believe in something, you have to know vaguely what it is and how it will play out. The other is that believing is more emotional - a sort of gut reaction. "That's why people feel belief and don't think belief," says Hamer, who is inclined towards the latter camp.
Getting a handle on the biological basis of belief is not easy. It is extremely difficult to study how faith in God's power to heal can actually heal, for instance. Luckily, there is an alternative. Faith in medicine is almost as ubiquitous as faith in God, and the effects are far easier to control and to measure. We know, for instance, that about 80 per cent of the effect of antidepressants derives from people's faith that they will work (Prevention & Treatment, vol 5, p 23). The influence of belief may be even stronger in alternative medicine. A study out last September showed that acupuncture seems to alleviate headaches no matter where in the body you stick the needles or how you twiddle them (British Medical Journal, vol 331, p 376). And countless medical studies have used placebos to show that belief is a major player in the healing process. "The best way to understand the scientific effect of belief is to look at the literature on the placebo effect," says Herbert Benson, director of the Mind/Body Medical Institute in Boston.
Put simply, the placebo effect is the biological impact of believing in a medical treatment. There is no doubt that it is a real and powerful force. The question is, how exactly does it work. Last year, Jon-Kar Zubieta at the University of Michigan at Ann Arbor published research that tackled the issue head-on. He gave 14 healthy men infusions to make their jaws ache. They were then given a treatment that they were told "may or may not relieve pain". In fact, it was only a saline solution, yet all the men reported less pain. And their pain relief was not just subjective. Using positron emission tomography, or PET, to scan their brains, Zubieta found that volunteers produced more endorphins, the body's own natural opioid painkillers, after receiving the placebo (Nature Neuroscience, vol 25, p 7754).
Combing his data for clues as to what was going on, Zubieta found differences in the way untreated pain and placebo-treated pain affected the brain. With the placebo, not only did people release more endorphins overall, they also released them in additional areas of the brain. These included regions involved in higher-order cognition such as parts of the rostral anterior cingulate, which helps determine how much pain you are feeling, the insular cortex, which receives signals from the body about pain, and the nucleus accumbens, which tells you how important it is. Zubieta also found differences between people who said in advance that they expected to get a lot of relief and those who were more sceptical. In the faithful, he found more endorphins were released in the dorsolateral prefrontal cortex, a cognitive area thought to be involved in decision making, interpretation and selective attention.
All this suggests that the cognitive experience of anticipating relief plays a major role in allowing it to happen. In other words, the evidence supports the hypothesis that belief is a conscious, rational process - a kissing cousin to expectation. And further evidence from behavioural studies seems to bolster this. First and foremost is the fact that to benefit, you have to know you are being treated - the placebo effect won't kick in if a sham medication is given covertly. Similarly, praying for yourself or knowing that family and friends are praying for you seems to produce some positive results, while being secretly prayed for does not (The Lancet, vol 366, p 211).
Experience also appears to be critical. That makes sense, as you have to derive your expectations from somewhere. A study in people with Parkinson's disease, for example, found that after taking a placebo people actually secreted dopamine, the very neurotransmitter they are short on, and at levels similar to that produced by drugs (Science, vol 293, p 1164). But all these patients had previously had positive experiences taking medicines. This is true for many of us. People with a long history of not being helped by conventional medicine, such as those with chronic pain, do not respond well to conventional placebos either. Nor do people with Alzheimer's disease, whose memory impairments or cognitive decline may make it hard to develop the kind of expectations that placebos might depend on. Likewise, children who have no preconception of a particular procedure such as acupuncture get no relief from it.
Perhaps it is not so surprising that expectation and experience are bound up with the placebo effect, which by its very nature is all about the belief that a treatment will or will not work. But underlying this effect is a more stable set of beliefs in the power of medicine in general. There's a direct parallel with other basic beliefs such as religious belief and belief in the evidence of our senses. Myriad such beliefs form the foundations of the way we see the world, and they tend to be very stable. We would be basket cases if every bit of conflicting evidence caused us to alter our world view. Imagine, for example, that you have slept in an awkward position and wake up with no feeling in your arm. You don't immediately assume that you are paralysed.
Yet sometimes we are forced to reassess our deep-held beliefs, and in some cases resistance to change can cause medical oddities. It is these strange conditions that Ramachandran studies to get an insight into the nature of belief.
Among the patients he has observed are a group with a condition known as anosognosia, usually caused by stroke. These people deny facts about their bodies, such as that they are paralysed. They will stare at an immobile arm, for example, while insisting they are throwing a ball with it. Ramachandran recalls one case in which he managed to get a woman in denial about the fact that her arm was paralysed to briefly admit it. He did this by providing her with an acceptable way to believe: he told her that he was injecting her arm with an anaesthetic and that it would be temporarily paralysed. After he injected her with a saline solution she did indeed notice that her arm couldn't move. To rule out mere suggestibility, he injected the other arm too, whereupon she complained that the anaesthetic wasn't working.
Ramachandran has studied many such patients. Not all are as resolute as this one. Most anosognosics make excuses, explaining why they don't want to move their paralysed limb - that they have arthritis, for instance, or that the other doctors have already poked and prodded so much that they are fed up. But he has noticed that only patients who have had damage to the right side of their brain confabulate in this way. People with left-side damage, by contrast, are acutely aware of their paralysis and tend to talk about it non-stop.
Such observations have led Ramachandran to suggest that in healthy brains there is a back and forth between believing the old and accepting the new. The left hemisphere, he maintains, tries to impose consistency, whereas the right hemisphere plays devil's advocate, trying to get us to question our beliefs in the light of new evidence. In people with anosognosia, he suspects that brain damage caused by the stroke somehow impairs the right hemisphere's natural scepticism. The left hemisphere is left on its own to uphold the status quo no matter what - even at the risk of becoming delusional.
Much more common examples of such disorders of belief, he suspects, are illnesses such as anorexia and bipolar disorder. People who have anorexia can be completely emaciated yet still look in the mirror and see themselves as fat. In bipolar disorder, the mania phase is often characterised by grandiose and apparently unchecked beliefs. The depressive phase is the opposite, a collapse of self-belief. It is generally accepted that these illnesses disrupt the emotions, so Ramachandran's suggestion that they also have to do with impaired belief systems chimes with the second hypothesis about belief - that it is emotional and akin to longing.
Hamer has raised this idea, arguing that belief - be it in God, medicine or whatever - slightly alters our emotional state. Just as feeling joy has chemical consequences in the brain, so, he speculates, does feeling faith. "Belief," he suggests, "is changing the tenor of the brain." Hamer thinks that belief is mediated by the same neurotransmitters - for example, dopamine and serotonin - that mediate other emotions. He has found, for instance, that there is a variant of a gene called VMAT2 that may be associated with greater spirituality. The VMAT2 protein seems to control the flow in the brain of monoamines, a class of neurotransmitters that includes serotonin and dopamine.
Interestingly, Zubieta's study also indicates a role for emotions. One of his most intriguing findings was that the more people suffered from the pain he induced, the more placebo effect they got. In other words, the greater their longing for relief, the more the endorphins flowed. Zubieta's working hypothesis is that placebos piggyback on the brain's innate painkilling ability, so believing that a treatment will bring relief merely engages this natural system more fully.
Perhaps belief is both a rational process and an emotional one. The picture is still very hazy but, at the very least, attempts to discover the biological underpinnings of belief highlight the fact that it is real: it does have measurable physical effects in our brains. More intriguingly, these effects have the potential to influence the outcome of events. This may even go some way towards explaining the role that self-belief has in helping us achieve our goals in life. If belief in our own abilities can actually bring success, then belief becomes a virtuous circle, a self-fulfilling prophesy. No wonder people are often so often so eager to believe in the first place.