beliefs are likely to be told by godly people that religious belief is ‘hard-wired’ into every brain, including ours. It is difficult to give up a self-serving metaphor, especially when the new metaphor, which is closer to the truth, is difficult to comprehend.
The neuroscientist Marco Iacoboni pointed out that, just as the casing of a computer is simply a container for the memory and the software of the computer, so, in the computer metaphor, ‘mental operations are largely detached from the workings of the body, with the body a mere output device for commands generated by the manipulation of abstract symbols in the mind’. However, it is now clear that ‘our mental processes are shaped by our bodies and by the types of perceptual and motor experiences that are the product of their movement through and interacting with the surrounding world’.3 Our mind is shaped by the way our body interacts with the world around us. Thus our brain contains maps of, say, our hand curving around a cup and of our body balancing itself as we walk over rough ground.
When I was a psychology undergraduate in 1948, we were taught that, in our interactions with the world, first we had a sensation, then a perception, and then a response which was some kind of action. Over the following years, neuropsychologists accepted what researchers were telling them, namely that sensation and perception were one process. It was still assumed that perception and action were completely independent processes. Iacoboni is one of the neuroscientists researching the functions of what have been called mirror neurones that are located in the premotor cortex. These neurones seem to be an essential part of our ability to imitate others. What this research has shown is that perception and action are not separate functions in our brain but are ‘simply two sides of the same coin, inextricably linked to each other’. Iacoboni explained, ‘In the real world, neither the monkey nor the human can observe someone else picking up an apple without also invoking in the brain motor neurone plans necessary to snatch that apple themselves… In short, the grasping actions and the motor plans necessary to obtain and eat a piece of fruit are inherently linked to our very understanding of the fruit.’4 That is, if your brain did not already contain a picture of what an apple was and how it could be eaten, you would not create motor plans to snatch the fruit, unless, perhaps, you had no knowledge of good manners and were so overcome with curiosity that you planned to seize and examine this strange thing.
What I had been taught all those years ago is now called the sensory-motor model of human action, whereas now we have the ideomotor model which ‘assumes that the starting point of actions are the intentions associated with them, and that actions should be mostly considered as means to achieve those intentions’.5 If you want to understand another person (or yourself) you need to know not just what that person does but why he does it.
In short, our brain interprets the world, and our interpretations become our intentions in acting on the world. But, if our interpretations are only guesses about our world, how can we assess whether our actions are likely to be successful? Answer: with our Bayesian brains.
Thomas Bayes was an eighteenth-century Presbyterian minister and mathematician. He created a mathematical theorem concerning the probability of an event occurring changing as more information is accumulated. A famous example of Bayesian brains at work is that scene where people are looking up into the sky and asking, ‘Is it a bird? A plane? No, it’s Superman.’ In this case, the Bayesian brain is working out the probability of the hypotheses of, first, a bird, then, a plane, and, with the best evidence, Superman himself, a conclusion, all without conscious effort on the part of the observers. Computers can use Bayesian methods of calculating the probabilities that arise in very complex data. As a Presbyterian, Bayes would have been pleased that his statistical method is used in computers to filter out immoral spam. My computer manages to identify all those email offers of Viagra and penis extension, but, unfortunately, it cannot distinguish these from the emails from that very august establishment The Sydney Institute in the city of that name. My Bayesian brain knows the difference, but my Bayesian computer does not.
We can make grave errors in deciding the probability of a particular event, but, according to Chris Frith,
Our brains are ideal observers when it comes to making use of the evidence from our senses. For example, one problem our brain has to solve is how to combine evidence from our different senses. When we are listening to someone, our brain combines the evidence from our eyes – the sight of their lips moving – and from our ears – the sound of their voice. When we pick something up, our brain combines the evidence from our eyes – what the object looks like – and from our sense of touch – what the object feels like. When combining this evidence, our brain behaves just like the ideal Bayesian observer. Weak evidence is ignored; strong evidence is emphasized. When I am speaking to the Professor of English at a very noisy party, I will find myself staring intently at her lips, because in this situation the evidence coming through my eyes is better than the evidence coming through my ears.6
When I am lecturing, I make constant assessments of the probability that my audience is interested in what I am saying. When I am talking about how we operate in the world, the response from most people suggests that they have not encountered the idea that they cannot see reality directly, or that the brain calculates probabilities in making a guess about what might be going on. I find that my audiences listen with a degree of attentiveness that they do not show when I am talking about matters with which they are familiar. I found this even in an audience comprised of highly educated people who placed great value on education. These were the parents of students at a famous public school. I had been asked to talk about communication between parents and their children. To explain why communication so often failed I needed to begin by explaining how we operate as human beings.
I have given this part of my lecture many times. I usually begin with something which I acquired from Ian Stewart, the Professor of Mathematics at Warwick University, but which I now pass off as my own.
Standing in front of my audience and with appropriate gestures, I say, ‘As I stand here everything seems totally real. I’m here, you’re over there, and beyond you are the walls, and beyond that what I can see through the windows. But actually, that isn’t what is happening. I have no idea what is actually here. What is happening is that my brain has created a picture of what might be here, and then it has played a clever trick on me. It has persuaded me that, instead of the picture being inside my head and I’m all around it, I’m in the middle and the picture is all around me. The same thing is happening to you. What you’re seeing is a picture inside your head, but your brain has tricked you into thinking that you’re in the middle and the picture is all around you.’
I go on, ‘If we could take these pictures out of our heads like a photo out of a camera and hang our pictures on the wall so that we can all walk around and look at them, we would find that no two pictures were the same.’
The next part of what I say reveals in the audience’s reaction how little biology is taught in our schools, or taught in such a way that the students do not see the implications of what they have learnt. Most of my audience – even when they are medically trained – find what I say next amazing. I run through all the features of the pictures where there would be differences. In the structuring of the depth and distances in each picture there would be differences which relate to the environment in which the person had spent the first few months of his life when he was learning how to see. Babies do not just open their eyes and see. They have to learn how to see. The baby’s brain has to set up connections between the reactions of the baby’s retinas when light strikes them and those parts of the baby’s brain which can become the visual cortex. If this learning does not take place at the precise time when it needs to take place, the baby does not learn to see, and what would have been the visual cortex is taken over by some other cortical function. Just what connections are set up in learning to see depend on the environment the baby is in. Those of us who spent our early months in rectangular rooms learned to structure depth and distance differently from those babies who were in round rooms, like kraals or yurts, or those irregularly shaped spaces that some babies, like those of refugees in Darfur, spend their first months.