WHY THE BODY NEEDS
A BRAIN
Brain, n. An apparatus with which we think we think.
Ambrose Bierce1
As bodies get more complicated they need ways to coordinate what is going in their different limbs and organs. But they also need to coordinate all of that with what is going on around them. In order to behave intelligently, we have to be sensitive to what is going on in the Super-Systems that surround us. To do that, we have evolved a range of ways of resonating with this big wide world: our special senses. And the most important of these is touch.
Skin
Everything occurs on the skin.
Hermann von Helmholtz
Skin is incredibly multi-talented. It is the leather pouch that stops us spilling out. It is also an important part of the immune system, being (usually) our first line of defence when toxic or dangerous things come our way. Its pores allow us some measure of temperature control through, for example, sweating and shivering. And skin protects us from the harmful effects of sunlight by producing the dark pigment melanin, which absorbs and dissipates ultraviolet rays. But skin is also our primary organ of touch. It is the original way in which all animals get information about their surroundings. It is our largest and most important sense organ. Skin takes up around 18 per cent of our total body weight, and it is worth every ounce.
Skin is at once our most basic and most sophisticated organ, and touch is our prototypical sense. We could not live without it, and the other senses are merely specialised forms of touch. One can live a rich life without vision, but without touch one is really in trouble.2 In its early learning a child relies heavily on touch: it feeds, sucks, clings, gets swung around, and later stands, walks, builds, falls and stands again. It never outgrows learning by moving and touching, even when language, imagination and reason have kicked in. It will learn to throw and catch a ball, ride a bike, dance, get on and off escalators, lift suitcases, feel the forces of a cornering car, make love, and swing its own baby in turn.
Touch is an action. We are ‘in touch’ with the world by moving against it, and feeling it on our skin. Touch occurs when skin and world move relative to each other, and that gives us useful information. We know ‘softness’ through the activities of squeezing or stroking, and ‘hardness’ through the physical impact of a fall or a cricket ball. The kind of touch tells us whether to approach or avoid. A punch, a rasp or a prick, and we draw back; a caress, and we snuggle in. Particularly in sensitive areas such as the hands or face, but in fact all over, the skin is densely provided with neurons that specialise in different kinds of touch. One set of nerve fibres, for instance, responds to pain, pressure and temperature as well as itches and scratches. It tells you that an object with a certain size, temperature, velocity and texture is ‘in your face’ or ‘on your back’. A different set responds selectively to touch that is slow and firm but gentle. Interestingly, these so-called C-afferent neurons3 take a different route to the brain, joining up with afferent fibres from the visceral core of the body, and thus acquiring a strong emotional tone to do with affection and security. We have a whole network of nerves designed to tell us when we are in touch with another human being who is safe and nurturing.4
We know the world, to a considerable extent, by remembering how it will feel if we stroke it, pinch it, prod it or tickle it. Through active touching we get the world to reveal itself, and we register those discoveries. If we were blind, we would depend on exploring the solid world in this way, and thus build up a network of expectations: if I moved my hand here, I would expect to feel the hard edge of the table; if there, the cool smooth curve of a bottle. Even on the brink of sleep my body expects that an arm stretched out thus should encounter the soft shape of your hip so. I am not conscious of this tissue of physical expectations and correlations, but I know they are there because when the hip is missing I become alert, and need to go and see if you, unable to sleep, are safely (if grumpily) drinking tea in the kitchen.
This is how all our senses work: by generating these interwoven webs of expectation that link movement to sensation. Even vision is like this, though it is less obvious. The world in the form of electromagnetic information rubs against our moving eyes, and from this I learn that, if things stay still, a flick of my eyes over there will result in a predicted shift in visual experience. According to the work of vision scientists such as Alva Noë and Kevin O’Regan, the visual world is not really a wraparound cinema screen; it’s that web of expectations that link movements of my eyes and head to changing visual sensations.5
Detailed experiments have shown that what we actually ‘see’ in any moment is much narrower and sketchier than we think. For example, experiments on what are called ‘change blindness’ and ‘inattentional blindness’ show that, unless we are actively attending to a specific location, we are really poor at spotting even quite gross changes that occur there. People talking on their cell phones very often do not see the brightly clad clown on a unicycle who rides past them. Searching for a friend at a concert, we bias ourselves to look for flashes of yellow, because we know she is wearing a lemony shirt. So we notice lots of yellow things, and fail to recognise our friend when she walks by, having slipped on her coat.6
This way of looking at vision is a shock to the Cartesian view of perception. We naively think of vision as giving us largely unproblematic, objective access to the world around us, uncontaminated by considerations of subjective need. We see what’s there, right, and then evaluate it and respond to it. We see ‘seeing’ as a receptive process, just noticing ‘what’s there’. But this way of looking at seeing obscures its deep relationship to doing and needing. To see, we need the world to rub against those specialised bits of skin called eyes – or our eye-skin to actively rub against the world, identifying its textures and edges.
It may be that we have become such predominantly visual creatures partly because we have (mis)interpreted vision in this Cartesian way. If we think of visual perception as decoupled from the other two aspects of the body, doing and needing, we are encouraged to view it as the closest of all our senses to that disembodied and dispassionate ‘mind’. ‘I see’, we say, when we mean we understand. Research on vision in psychology and physiology vastly outweighs that on all the other senses put together – because of its Cartesian bias.
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What is going on in the rest of the body alters the way our skin behaves, so our ‘somatosensory perception’, as it is called, is constantly being tuned and primed by what is going on in the brain and the gut (for example). Just as the permeability of the membrane of an individual cell changes, depending on what the cell as a whole needs to absorb or expel, so our big ‘membrane’, the skin, alters its behaviour in the light of what is going on elsewhere. Though we may not be aware of it, the autonomic nervous system is constantly modulating the activity in our sweat glands, and this changes the electrical conductivity of the skin, formally called the electrodermal activity (EDA).7 Stick two electrodes on your skin, and a meter will show the fluctuating level of the skin’s ability to conduct electricity. The sweatier you are, the greater the conductance. Because our skin is hooked up with changes occurring all over the body, the EDA is often used as an indicator of our overall level of physiological arousal. We know that we may flush with fear or embarrassment, and our ‘hair stands on end’ when we are excited or enraged (as threatened cats’ and dogs’ hackles rise, too). But skin is involved in the life of the intellect as well as the emotions. When we face a tricky decision – as in deciding the answer to an item on an intelligence test, for instance – our skin is as involved as our brain. In fact Damasio and his colleagues have found that the EDA can be a more sensitive indicator of our thinking than our conscious minds are. Intelligence is a whole-body happening!8
Emotions also change the colour of our skin, by the way, as blood is sent or withdrawn. We blush with shame or go pale with fear – so skin colour acts as a very important social signal. The other senses have the same capacity as the skin to act as social signals. The muscles of the nose and mouth signal disgust or amusement. We sniff in disapproval. Eye movements can give away our intentions: our pupils dilate when we are feeling sexy. According to folklore, even our ears go pink with pleasure and burn when we are being talked about.
All the senses show the same close association between perception and action. I smell mostly by sniffing. I get a whiff, and then I intensify my smelling by inhaling sharply. I taste by chewing and smacking my lips. I don’t just hear, I listen by turning off the radio, becoming very still and cocking my head in the direction of the noise. Even when I am apparently still, perception is dynamic. Nose and mouth are full of specialised receptors that are literally touched by a wide range of molecules. The ears are designed to be touched by pulses of pressure in the air, just as our eyes are designed by evolution to be stroked by a spectrum of electromagnetic energies.
The fact that movement is integral to perception is starkly demonstrated by a famous experiment that every psychology undergraduate learns about.9 Two kittens were yoked together in a kind of primitive two-seater carousel for the first few weeks of their lives. One had its feet on the ground, and could at least walk round in circles as it wished. The other was forced to lie in the cradle opposite, and be carried around at the whim of its more fortunate sister (see Figure 4). This devious device ensured that the two kittens had the same kind and amount of visual experience, but for one this was linked to its own movement, and for the other, it was not. Despite plenty to see, and despite no obvious damage to its visual system, the passive kitten never learned to see properly. It couldn’t recognise objects, navigate its way around a room, or see in depth. Deprived of the opportunity to link movement and vision in a meaningful way – to discover how the world changed as it changed – the kitten never learned to see meaning in the world. If human babies are swaddled and bound so they cannot move, their perceptual and cognitive development quickly goes awry. Those poor orphan babies in Ceauşescu’s Romania, stuck in cots for months on end, did recover somewhat, but never fully.
Fig. 4 The Held and Hein cradle. Both kittens get the same visual experience, but for only one of them is this linked to their own actions.
Needs, Deeds and See’ds
Our bodies are defined, broadly, by three sets of considerations. The first, and most basic, is: what do I need? At every moment, the body is alive with a variety of concerns and priorities, all of which have a degree of urgency. I want to get this chapter finished, and I need to get to the shops, and I have to break off at some point and deal with the important emails, and I have to remember to put out the bins … Some of these concerns are physiological and some reflect longer-term desires, interests and obligations. Some spring from my beliefs and attachments and my self-image. Some of them are mutually compatible, but others compete or are even contradictory. (I want to see myself as a morally admirable being, for example, but I am late for the meeting so decide not to stop and help the person in distress – and feel guilty.) Some of these, like the need for air, stay pretty constant over my lifespan; others develop, and some peter out, along the way. Generally, though, in the course of growing up we develop a rather large and entangled range of priorities. They constitute a substantial, fluctuating, partly conflicting portfolio of concerns: all the things I have on my plate right now. Let’s call these our Needs, for short.
Second, there is the collection of my reflexes, skills and capabilities: the know-how I possess, all the way from deeply embedded and unconscious regulation of my blood-sugar levels (assuming I am not a diagnosed diabetic) to the learned expertise that enables me to concoct a tasty meal out of left-overs, or indeed write a book. Again, some of these are deeply wired in and apparently beyond conscious control; others are more or less unconsciously picked up along the way as I incessantly tune my capacities to respond to the changing world; and some are acquired deliberately and often with a good deal of conscious effort and practice. I have the ability to carry on typing, or make a cup of coffee, or play a sliced backhand, or sing the Hallelujah Chorus, or … or … or … These skills in toto constitute my portfolio of capabilities. For short, I’ll call them my potential Deeds.
And finally there is, at every moment, a portfolio of opportunities being revealed by my senses. Let’s call them See’ds. In my current world, as it appears to me, there is a television that could be switched on, a window that could be opened, a magazine that could be read, a keyboard that could be typed – but not a submarine periscope that could be lowered, or a glamorous film star yearning to be kissed. Perception’s job is scoping out the possible ‘theatre of action’ – a sense of all the things that current circumstances permit me to do – so that I can select and craft my actions appropriately. The Yiddish word klutz describes a person whose actions constantly miss the mark because they misread the situation. (Think of Mr Bean, Lieutenant Frank Drebin or the magnificently incompetent Inspector Clouseau.)
Why you have a brain
At any moment I am a buzzing swarm of Needs, Deeds and See’ds. And my job – the function of my intelligence – is to resolve all this shimmering mish-mash of information into an answer to the perennial, deceptively simple-sounding question: ‘What is the best thing to do next (all things considered)?’ And for this I need a brain. An amoeba has few Needs, even fewer possible Deeds, and very limited See’ds, so it doesn’t need a proper brain. But I do, because deciding on the best thing to do next is often, as my Oxford philosopher friends put it, a deeply non-trivial problem. Sometimes this multivariate equation is easy to solve: it is literally a no-brainer. When I am in the middle of a well-practised routine, like cleaning my teeth, a sequence of actions unfolds automatically (unless I am disturbed by an event or a thought). I have plenty of habits that tell me, ‘When I need to do X, and the world is like Y, then do Z’. When I want to make a white sauce, and I am in my own kitchen, I go to the shelf by the door and get the flour.
But when I want to resolve an upsetting conversation with my wife, and she has gone off to work in a frosty mood, then I – my body-brain – may need to consider a wider and less routine array of options. I could send her a friendly and apologetic email and offer to take her out for dinner and try to work it out – but the outcome of this is far from certain. She may not yet be in a conciliatory mood. Even going to fetch the flour is thwarted if I have forgotten to replenish it. Every action I make is a ‘best guess’, based on expectations extracted from the past, which may, in the event, go wrong or prove inadequate. So there is always the need to reconsider, think on my feet, and recompute what ‘the next-best thing to do’ might be. That’s where the intelligence of the body is most importantly to be found: in resolving unfamiliar combinations of Need, Deed and See’d into optimal, customised responses to novel situations.
This need to find an optimal (or at least adequate) resolution of three complex sets of factors is fundamental for all animals, so it is not surprising that the body-brain is evolutionarily designed to do it. And this means that, far from Needs (motivation), Deeds (action) and See’ds (perception) being three separate compartments, in need of being tied together by ‘the mind’, they are in fact knitted tightly together in the structure and functioning of the body-mind itself. Brains evolved to support their bodies in doing that knitting. Brains evolved to help increasingly complicated, mobile bodies deal with problems of coordination and communication that they could not solve on their own. It was – and remains – their raison d’être. Intelligence did not arrive from ‘elsewhere’, like a newly appointed Managing Director, proud of her Harvard MBA expertise, ready to ‘kick ass and take names’ in the corporation of which she was now the Boss. That intelligence pervades the body and its servant, the brain. The brain is the central information exchange of the body where these three swarms of factors can come together and, through communication, agree on a plan. The brain does not issue commands; it hosts conversations.
Needs, Deeds and See’ds are automatically and very nearly instantaneously integrated in the brain.10 There are systems and pathways in the brain that link perception and action directly, so that, within a few hundredths of a second of my seeing you begin to reach out for the last piece of sushi, my own motor cortex is already beginning to construct a pre-emptive strike (which, in the interests of other considerations such as friendship, may, another few hundredths of a second later, be vetoed). At the same time as my brain begins to pull together the threads of the action, the motor cortex is telling the sensory cortex what changes in the world to expect as a consequence of my launching the action. The somatosensory cortex, the bit that registers changes to the body, is being primed to expect changes in the way my right arm feels, and the visual regions of the brain are anticipating seeing a hand appear, wielding a pair of chopsticks and moving rapidly towards the dish on the restaurant table between us. As a result of lots of previous actions, my movements are partially and automatically encoded in terms of their anticipated effects on perception.11
There are many demonstrations of this tight coupling of action and perception. Imagine that you are shown 2D pictures of two 3D objects and asked if one can be rotated so that it is identical to the other. Not only does the length of time to do this depend on the angle of rotation you have to turn the shape through; brain imaging shows that the motor areas of the brain are active while you are doing the task. You don’t just watch the shape being spun round; it appears that your brain actually has to do the spinning. In another appealing demonstration, Rob Ellis and Mike Tucker at the University of Plymouth showed people a range of pictures one at a time, and they simply had to press one button if the picture was of a kind of water jug, and another button if it wasn’t. All the jugs had handles, and they were photographed in profile so the handle was prominent – but the pictures varied in whether the handle was on the same side as the ‘Yes’ button or on the opposite side. People were much faster at correctly pressing Yes if the relevant button was on the same side as the handle! Seeing the picture automatically activated the appropriate hand movement for picking it up, and if this was compatible with pressing the button, the two forces combined to make people faster. If the two movements are incompatible, their conflicting tendencies slows us down. Seeing is doing, apparently.12
In practical terms, what you can do about something influences the way it shows up in your perception. Without touching them at all, you see objects and pictures that are placed near your hands differently from those that are further away. They look clearer, they are looked at longer, and it is harder to shift your attention away from them to another object. Richard Abrams and his colleagues at Washington University in St Louis speculate that this is because things closer to the hands are more likely to be things that are relevant to us – such as tools or food, for example – and so automatically take priority over other aspects of the world.13
Which brings us on to the embroiling of need in perception. Just as action and perception are tightly stitched together, so are they bound in with information concerning values, concerns and interests. Perception is not neutral: it is already weighted, with no conscious thought or awareness, by a host of motivational factors. Hills actually look steeper to people who are tired, ill, elderly or wearing heavy backpacks. The physical cost of climbing the hill is already factored in to the way the hill looks. People who are afraid of heights judge a balcony on which they are standing to be further from the ground than people who don’t have that fear. And golfers who have just had a good round literally see the hole as bigger than when they have had an off day. Hoping, wanting and fearing are already dissolved in perception, in other words. We don’t have to add them in deliberately.14
Our bodies understand ideas in terms of what they are good for, and how we make use of them: not just in terms of the features by which we recognise them. When you ask someone what a ‘ball’ is, in the context of a discussion about football, bits of their motor cortex light up that correspond to control of the legs and the act of kicking. Ask them the same question in the context of talking about tennis, and the embodied ‘meaning’ that is automatically activated involves arms and shoulders. If you had just been talking about your teenage daughter’s school prom, ‘ball’ would activate responses to do with dancing (as well as visceral anxieties about the cost of the dress). When I hear ‘John took the book’ and ‘John took the needle’, the motor cortex primes itself to make two quite distinct kinds of grasping action – even though there is no question that I have actually been asked to ‘take’ anything literally myself.
Even social emotions such as embarrassment change the way we see the world. In a rather unkind experiment, Emily Balcetis and her colleagues made their volunteers play a game in which, if they were shown a picture of a farm animal they would then have to judge a singing competition, whereas if a picture of a marine animal came up, they would immediately have to do their own karaoke performance and be judged on it by others. On the critical trial, they were shown ambiguous pictures such as the one in Figure 5, which could be seen either as the head of a donkey or the body of a seal. People were much more likely to see – literally see – the version that got them off the hook of having to perform!15 This was not a matter of cunning thinking; it was the body-brain doing what it is designed to do – far faster than thought.
Information from your viscera, your muscles and your senses arrives in your brain through different gates, but within an instant the different types of information are chatting animatedly to each other. Especially as you get to know the world better, your brain circuitry remembers what sights and sounds went together, with what actions and reactions those sensations were associated, and what the felt consequences were. All this is filed away so that, next time, you will be able to integrate the various considerations in a smoother, faster and more satisfactory way. There is always the chance that my best-laid schemes will go awry but, on balance, my brain gets cumulatively better at resolving the issue of what ‘the best thing to do next’ should be.
One way of putting this is to say that our brains are profoundly egocentric. They are not designed to see, hear, smell, taste and touch things as they are in themselves, but as they are in relation to our abilities and needs. What I’m really perceiving is not a chair, but a ‘for sitting’; not a ladder but a ‘for climbing’; not a greenhouse but a ‘for propagating’. Other animals, indeed other people, might extract from their worlds quite different sets of possibilities. To the cat, the chair is ‘for sleeping’, the ladder is ‘for claw-sharpening’ and the greenhouse is ‘for mousing’. To me, my old university friends are ‘for reminiscing and silly joke telling’; for some of our long-suffering partners, they might not be for anything much except perhaps ‘for putting up with’. A block of wood that affords only ‘burning’ to me might well afford ‘displaying’ to an inveterate beachcomber, or ‘carving’ to a sculptor. My laptop affords ‘reprogramming’ to my IT-savvy friend Charlie, but only ‘word-processing’, ‘emailing’ and ‘internet-searching’ to me. To someone who is recovering from a stroke, the stairs in her house may no longer afford ‘for ascending’, and they will, in consequence, look different.
In fact, we could see the deep structure of the brain in terms not of Needs, Deeds and See’ds but in terms of a different set of basic concepts that have already combined these (see Figure 6). If we meld perceptions and actions – if we see perception as deeply imbued with the possibilities for action – we could call the result affordances. An affordance is a scene already parsed in terms of the things I could possibly do. If we blend perceptions with our concerns, we might call these opportunities. An opportunity is an aspect of the world seen in the light of my current needs, interests or values. And if we combine actions and concerns, we could speak of intentions. An intention is an incipient action that already has a sense not just of possibility but of purpose.
This flipping of the categories is like the transposition we can make of the primary colours. In primary school, we are told that the three basic colours are red, yellow and blue, but when you replace your printer cartridges, you will buy cyan, magenta and yellow. What look like secondary or combined colours from the primary school perspective can, for some purposes, be better seen as the basics. I think that may well also be true of the three ‘primary’ hues of the functional human body. It takes further work by a sophisticated nervous system to pull affordances, opportunities and intentions apart, and decouple perception, action and motivation from each other. To see a situation with judicial impartiality does not come naturally to us. It is a difficult cognitive trick, which takes years of schooling – studying things you do not care about and cannot make use of – to master.
Fig. 6 The integration of Needs, Deeds and See’ds.
If we waited till the world showed up, we would often be caught napping. By the time she can actually see the lion, it may be all over for the gazelle. If I wait till the guests arrive to remind me that I need to cook the meal, we will have a late dinner and disgruntled diners. So another key design feature of the brain is anticipation. If I can make a good guess as to what the world is about to do, I can prepare my response and mesh more smoothly and speedily. As neuroscientist Marcel Kinsbourne says, ‘Anticipation is a wager based on previous experience. It readies a response to an event that has yet to occur.’16 The world and I become, as much as we can, like familiar dancing partners: we can flow and improvise together because my deep bodily knowledge of you, and yours of me, enables us to ‘read’ the slightest shift in the pressure of a hand, or the angle of a hip, and begin to respond almost before the signalled movement has actually begun. That’s why, as the great psychologist William James, observed, every moment of our conscious lives is not just ‘here now’, but is infused with a continuing sense of the impending and the receding. To coin a phrase, time past and time future are both contained in time present.
We store our rolling knowledge of the world in terms of such expectations. I know what is over there not because I can see it, but because I have a pretty good idea of how my sensory experience would change if I flicked my eyes and angled my head in that direction. I anticipate how my movements would influence my perceptions, so my construction of the world is a fine tissue not of actual scenes and objects but of these predictions. ‘I believe there is a tree over there because I know how to make it present to my senses should I need to.’
How does prediction work? At its most basic, by what is called ‘spreading activation’. The brain is just a giant tangle of interconnected wiring with activity (electrical, chemical and physical) running through it. Some of the joints in this tangle are worn by experience, so when a pulse of activity comes to a junction, it will, all other things being equal, take the path of least resistance. As trains of pulses travel around the network, they can change its behaviour in two ways. They can leave a lasting facilitation of the chosen pathway, so that future pulses are more likely to go that way. Or they can leave an amount of activation behind, so that the path is primed, but not irreversibly changed. Some of these dollops of priming fade quite fast, but others can be ‘chronic’, in that they can change the routing in a functional but not a structural way. Both structural and functional changes are mechanisms of prediction. Note, by the way, that the words anticipation, prediction and expectation refer, in this context, to the way the brain is working, and not to any kind of conscious experience. Many predictions bias the behaviour of the body-brain without themselves becoming conscious.
Prediction streamlines the process of perception itself. Several researchers have recently picked up on suggestions by the nineteenth-century German physicist and physician Hermann von Helmholtz and spun these into an intricate new theory called ‘prediction coding’. Basically, the brain is constantly generating its best guess about what’s out there, and then feeding predictions, based on that guess, out to the different sensory receptors to create a downward tide of centrally generated sensory expectations meeting an incoming tide of sensory information. When they meet, any signals that match a prediction are cancelled out: there is no need to forward that information further up the incoming chain. Only information that is not expected gets passed up to a higher level, where predictions are adjusted or a whole new set of expectations are activated that do better justice to the input, and they are propagated back down in another wave of anticipation.
Through as many cycles of this process as are necessary, and often all in a flash, the brain finally settles for a good-enough, though always provisional, hypothesis about ‘what is out there’ and how it meshes with my current portfolios of concerns and capabilities. And this hypothesis incorporates already half-constructed plans and programmes for action. (‘Ah – there goes the baby monitor – just as I’m trying to play this tricky hand of bridge … what kind of cry is it?’ I mouth ‘sorry’ to the rest of the table, mime requesting a pause in the bidding, then incline my head towards the speaker, hold my breath, and await the next cry … OK, maybe just a sleepy whimper … doesn’t have that sharp edge it does when she’s upset – I’ll see if I can play this hand out and then go and check …)
Though this sounds complicated, it is actually highly efficient in terms of the ‘bandwidth’ of information-processing capacity that the system needs.17 And there is a good deal of neurophysiological evidence to support it.18 There are indeed massive outflows from the ‘higher’ processing centres in the brain down to ‘low’ levels of processing in the eyes, ears and skin. But what it means is that we never do perceive ‘what’s really out there’. Our perceptual world is always powerfully imbued with the knowledge, needs and capacities our body-brains bring to the situation.
Perception is a fabrication – a hallucination. But it is a hallucination that is constrained by the facts. It is put to the test of experience time and again, and if it works, it stays. And this is yet another kind of anticipation. If I act on the basis of the perceptual model – a tapestry woven out of threads of Need and Deed as well as See’d – does the world react in the way the model says it should? If, having won the hand, I find the baby lying in a funny position and making faint mewing sounds that I don’t recognise, a variety of powerful reactions kick in – one of which is my brain urgently updating its web of interpretations and expectations. Next time the monitor goes, my wave of predictions (and bodily reactions) will be different.
Finally, there are the predictions of what the sensory consequences of making that action will be. If I throw the ball so, I should see a trajectory rather like this. If I let go of the bottle and I am standing on the stone flagstones in the kitchen, then I can anticipate the length of the delay before I hear the sound of breaking glass. When the motor cortex is planning a movement it sends a carbon copy of the instruction to the sensory cortex, effectively saying, ‘I’m about to do this, and so, all being well, you should be about to experience that.’ If I try to tickle myself, the effect is underwhelming – because my brain can tell what is coming and cancel it out. (The very first paper I ever published in psychology, back in 1975, was entitled ‘Why can’t we tickle ourselves?’.)19
This ability to anticipate how what I do changes what I experience gives us another way of streamlining our operations. As we saw above, what is predictable is often of less interest than what is not, so we can cut costs by skimming over the matches and concentrating on the surprises. This is vital, because it is from the unexpected that we learn the most, and it is also the unexpected – that for which we are unprepared – that can be dangerous or disruptive. In addition, this kind of prediction enables us to tell the difference between changes in the world that are brought about by our own actions, and therefore possibly under our control, and those that occur independently of what we are doing, so are beyond our immediate control. How we draw this distinction makes a big difference to how we treat events.
One of the benefits of being able to make this distinction is the fact that the visual world stays steady as we move our eyes about. As we look around, or as we read a page, our eyes are flicking about all over the place. The patterns that fall on the retina are changing continuously and grossly. Yet we experience the world as both stable and largely unchanging: a stationary backdrop against which unexpected movements (as well as disappointments) instantly stand out. This stability, in the face of so much change, is achieved by the brain using what it has just seen to anticipate the visual changes that its own eye movements are likely to make and cancelling them out of the visual equation. Close one eye, and nudge the outside corner of the other with a finger. You will see the world move. Even though it is your own finger that is causing the movement, your brain has not set up the same kind of cross-referencing between ‘retinal displacement’ and ‘fingertip movement’ that it has for ‘direct brain-initiated eyeball movement’, so the sensations are not cancelled out.
Fig. 7 A Kanitzsa illusory pyramid.
Where the correspondence between action and perception is very strong and familiar, the action itself can generate the perception that normally goes with it, even when it isn’t there. If you and a friend go into a pitch-black room and she waves her hand in front of you, you might feel the slight disturbance of the air but you won’t see anything at all. But if you wave your own hand, you will have the powerful impression of being able to see your hand. Your brain fills in the gaps and you see what you would normally expect to see, in just the same way as the more familiar visual illusions, like the Kanitzsa figures (see Figure 7), replace what is actual with what is probable. You ‘see’ the illusory edges and depth because your brain assumes that the reason the black circles have bits missing is because there is something in front, and also that the different shades of grey reflect 3D shadows – so it helpfully doodles on reality to make it fit with that expectation.
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All told, the science of embodiment asks us to adjust our understanding of the brain in several ways. The brain by itself is not the physical substrate of ‘mind’: we can’t just take all the clever things that we used to attribute to the ghostly mind and plop them into the brain, leaving the rest of the body to be – in George W. Bush’s immortal coinage – misunderestimated in the same old ways. Body and brain function as a single unit. Though parts of the body can and do talk to each other directly, they also need to send missives and emissaries to the standing conference in the brain, where the really knotty problems and conflicts can get ironed out and prioritised.
Nor is the brain organised into a neat series of processing steps, like an old-fashioned production line, that lead from perception, through thought and memory, to action. Though different kinds of information do enter and exit through different doors, once they are through the doors what goes on in the brain is much more like an animated party than a game of Chinese Whispers, with Ears and Skin, Fingers and Shins, Lungs and Intestines all chatting to each other. There is no separate compartment called Memory; memories and expectations are the stuff of all of these conversations. And there is no Chief Executive who steps in to resolve disputes or correct impressions on the basis of her higher experience and intelligence.
These insights offer us a new logic of the brain, and a non-Cartesian way of thinking about its place in the body. But we can do better than that: we can delve into the real-time workings of the brain and the body, and see up close how some of these conversations happen, and where. That is the business of Chapter 5.