Darwin's Island Page 10
The face is a real mirror to the soul. Even a brief glimpse reveals the presence of another person, identifies who it might be and gives a strong hint as to what its bearer will do next. Most westerners interpret a set of features with a quick triangular scan of both eyes and the mouth, each of which say a lot about identity and state of mind - but the Chinese tend to concentrate their attentions instead in a fixed look at the nose and pick up the general expression of the whole visage in the background. Scans show that when someone flashes into view, the brain first notes his or her presence, then identifies who it might be and last of all of tests their mood: this is a face, it belongs to Fred, Fred is furious. It processes a portrait twice as fast as a picture of other objects. A certain part lights up about a tenth of a second after a face is first seen, notes its identity about a fifteenth of a second later and takes even longer to interpret what humour the person might be in.
Some expressions are easier to identify than are others. The smile is coded deep within the skull and everyone has an inborn ability to assume it. As Darwin noted, babies born blind smile without difficulty and (as he did not) blind athletes raise their arms in the air in a chimp-like gesture of triumph when they win. Children find it easier to pick out expressions of good cheer than they do those of fear or disgust. Women smile more at strangers than do men, while men are worse at working out mood from a slight movement of the lips. A lopsided grin to the right is seen by most of us as more joyful than is its equivalent on the left. Even sheep, when given a choice of a smirking or a sombre shepherd from whom to take food, prefer the cheery individual. We smile or raise our arms not to reassure ourselves that we are happy or proud, but to tell others how we feel. Context is all; when Chelsea score, fans respond with roars of triumph rather than smiles of delight, but gold medal winners as they stand on the Olympic podium have wider grins than do those who have gained bronze.
Signs of delight or terror seem simple enough, but there are real differences in the ability to decode them. I have a talent that illustrates that fact, for I can waggle my eyebrows. It began in school when I was rebuked for glowering. I then tried dumb insolence with a one-brow grimace rather than the full two-brow scowl and in time it became easy to alternate. It is still my occasional habit to amuse small children with the trick - and almost always they smile back. Unfortunately, an occasional infant screams instead. The signal is clear but the response uncertain.
Both steps can go wrong. Some people cannot tell individuals apart from their faces and use clues from voice or clothes instead. In one instance, a litigant wandered into court and discussed his case with a barrister - not his own, but his opponent’s. The context was right; a lawyer, with a gown, in a courtroom. The face alone did not fit. Needless to say, he lost. Face-blindness may be caused by a stroke, but a certain form runs in families with perhaps just a single gene involved.
Other unfortunates lose the ability to broadcast their emotions. For some reason - injury, infection, cancer or brain haemorrhage - the facial nerve no longer works and the patients cannot express their feelings. They find it hard to assume looks of happiness, fear or surprise, and their wives, husbands and friends soon notice the problem. The condition might appear to be trivial, but in fact causes real distress and sometimes even suicide, most of all when an attempt to smile emerges as a grimace or a leer because the eyebrows - usually lifted at a happy moment - refuse to obey instructions. Some people have their brows surgically moved upwards (which gives them a permanent look of surprise), while others grow a long fringe that hides the offending forehead. The readiness to take such steps shows how much a signal of mood is a passport to society.
Emotions marked the first real attempt by science to infer the action of the mind from its external signs. Scientists now study the activity of brain cells rather than of facial muscles as they try to understand our inner feelings. The use of electricity - and of the sophisticated electronic devices that depend on it - in psychology has become a science of its own. It was first expounded in Charles Darwin’s book.
The ancient Greeks had used electric fish to treat headaches but for many years the galvanic fluid was no more than an entertainment. An entire community of monks was once connected by a mile-long iron wire and made to jump for the amusement of the King of France (castrati were tested to see if they acted as insulators, but they did not). Emotions contains several pictures of faces stimulated by shocks to give expressions that resemble the natural look of horror, rage and the like. They came from the French physician Guillaume-Benjamin-Armand Duchenne de Boulogne. Duchenne is best remembered for the muscle disease named after him but he also studied the expression of what he called the ‘passions’, using electrodes touched to different parts of a countenance to stimulate the muscles. He was the first to notice that a genuine smile involved raised eyebrows, and his machine could easily activate those ‘sweet muscles of the soul’ to simulate a happy beam. He even made the visage of a decapitated criminal assume a simulacrum of pleasure with a probe upon its cheek. Duchenne chose as his main subject an aged man of feeble intellect, for he ‘wanted to prove that, despite defects of shape and lack of plastic beauty, every human face can become spiritually beautiful through the accurate rendering of emotions’. His pictures first came to public attention when they were published in The Expression of the Emotions. They played an important part in Darwin’s attempts to give an objective account of expressions of pleasure or pain.
The machines have marched on. Where Duchenne used a battery, a metal rod and a plate-camera, scientists in search of the springs of sentiment now depend on electro-encephalograms, positron emission tomography or functional magnetic resonance imaging (FMRI). Tiny electrodes are used to activate single nerve cells, while the EEG and its relative the magneto-encephalograph pick up electrical activity within the skull. PET scanners use a sugar marked with a radioactive label which is taken up by active parts of the brain and then detect its decay products. The fMRI machine, in contrast, senses tiny changes of blood flow through the grey matter from a shift in the magnetic properties of the red pigment haemoglobin as it gains or loses oxygen.
Marvellous as such techniques are, they run into many of the problems that plagued Charles Darwin. He had found it hard to decide just where the jaw ends and the cheek begins or to identify the precise arrangement of facial muscles. Today’s arguments about the boundaries between areas of the brain as defined by electronic scans - confidently coloured and labelled as the images might be - reflect his own doubts about the anatomy of the human countenance. Some claim that particular emotions can be mapped to a definite part of that organ. Others see the brain - as he saw the face - as a connected structure, with most sections contributing to most of its functions. Any attempt to pinpoint centres of anger, joy or despair might be of its nature a mistake.
Another problem for both the nineteenth and the twenty-first centuries comes from the need to describe broad sentiments in narrow terms. Darwin was happy to talk about dogs in a ‘humble and affectionate frame’ of mind - but how is it possible to put figures on humility or affection? Objective fact soon slides into mere interpretation and Expression was itself not immune from that temptation. Its photographic plates are not originals but engravings, some touched up to make a point. A mad lady with tousled hair was given a furrowed brow by the engraver and a screaming infant was made to look even more miserable than before by copying the portrait and re-photographing the sketch (the picture sold hundreds of thousands of copies to a gullible public). The stream of lurid images of centres for pain, passion and pleasure that decorate the scientific literature and leak into the press are also in some senses fakes. Digital information is processed in a complicated and sometimes subjective way to make a picture which is often rather more than the sum of its parts.
A final difficulty for both the Victorians and their descendants was to find subjects who were willing to display their emotions to the world. Duchenne set up a theatre in which the public could be delighted by a
ctors galvanically activated to produce an air of grief or delight. Many of Expression’s pictures are also based on members of that profession. Among them, a bearded thespian looks remarkably implausible as he strikes his attitudes. Actors still play an important part in neuroscience. Their photographs are taken as they simulate a mood and are then shown to subjects whose brains are scanned to see which bits light up. Many of the images look just as posed as do those of Darwin’s theatrical friend. The artistes overdo the job, often to a bizarre degree. People shown pictures of frightened or unhappy people taken from real life have far less of a nervous response than they do to images of those who simulate a mood as they strut and fret upon the laboratory floor. Most of us find it harder to interpret the sentiments (apart from laughter) in silent clips of Hollywood stars from Dustin Hoffman to Meryl Streep than we do the simulated joy or terror of a ham actor - and yet the hams are used as raw material for experiments of huge technical sophistication and expense.
Many claims have been made that particular parts of the brain respond to the sight of a happy or miserable countenance and that they prepare the nervous system to beam back or look sympathetic in return, but they have been hard to replicate. Because light comedy is a subtler form of entertainment than is Greek tragedy, the scientists who study that great theatre of emotion, the face, often focus instead not on mild signs of contentment or sadness but on expressions of horror and dread that might provoke an unambiguous response in those who see them.
A blank stare is a signal of terror and Shakespeare knew as much. A furious Othello says to his supposedly unfaithful (and frightened) wife Desdemona before he kills her: ‘Let me see your eyes.’ We have larger eye-whites than any other primate and take more notice of them, for the mouth is far more important than the eyes as a chimpanzee emotional signal. We process eyes quicker than any other feature and fearful, stretched-open eyes even faster - and women do the job better than men. One woman could not recognise a picture of a terrified individual because she did not look at the eyes. When instructed to do so she at once understood the subject’s frame of mind.
The brain’s main activity in response to a frightened look takes place in a pair of structures called the amygdalae. They are almond-shaped groups of nerve cells deep within the temporal lobes, the side sections of the brain, one on each side, embedded into what is sometimes seen as the organ’s most primitive parts. Each is connected to other brain centres, to the hypothalamus - that hormonal bridge between the nervous system and the bloodstream - to nerves that feed from pain receptors and from the eyes, and, in primates more than other mammals, to nerves to and from the face itself.
Animals in which the structures have been damaged find it hard to pass the classic test in which fear of an electric shock becomes associated with the sound of a bell. Experiments on monkeys in which those parts of the brain were cut out showed that the unfortunate creatures in addition lost their ability to recognise familiar objects, together with their nervousness about humans, and a mother’s affection for her infant. Human patients with damaged amygdalae have similar problems with emotionally draining tasks. The amygdala is also involved in memory. People recall where they were on 11 September 2001 with its help, but those in whom the structure is damaged remember the Twin Towers disaster no better than what they had for breakfast.
The amygdalae are busiest when a frightened gaze is directed straight at its target - which fits Darwin’s idea that a countenance stricken by terror is an immediate signal of danger. A few people have such severe brain damage that they perceive themselves as blind - but show them a scared person and the amygdala lights up. We are slower to notice the racial origin of an angry than of a happy face, so that fear has priority over familiarity. In the United States, images of black people shown to whites stir up more activity than do those of individuals of their own skin colour.
The case for the amygdala looks persuasive but, as usual when it comes to the contents of the skull, real life is not simple. Other parts of the brain are also involved in the response to a terrified countenance. The amygdala lights up in response to a whole face rather than just the eyes, and does so to some degree whether or not the subject shows signs of alarm. Its main role might be to notice new events, whatever they might be, rather than to make a specific response to a particular emotion.
The structure helps to process a nerve-transmitter called serotonin (which is also involved in temperature control, sleep, hunger, lust, response to injury, liver repair and more). Many antidepressants work because they change the way in which serotonin is broken down, or taken into cells. Variation in the ability to respond to or to make the substance might be behind individual responses to fear. Some people are terrified even by the simplest problems of society. Darwin writes of a dinner party given for a man who, in response, ‘did not utter a single word; but he acted as if he were speaking with much emphasis. His friends, perceiving how the case stood, loudly applauded the imaginary bursts of eloquence, whenever his gestures indicated a pause, and the man never discovered that he had remained the whole time completely silent.’ The unfortunate fellow could now be comforted with the information that he may have a more active amygdala than normal and that his nervousness might be treated with drugs that alter his body chemistry.
Inborn errors in the ability to synthesise serotonin make some people sad, angry or suicidal. A gene whose product helps remove the chemical from the junctions between nerve cells comes in two common forms, one better at the job than the other. The less active type is more frequent among people who are anxious, neurotic or depressed - and its bearers are less able to decode expressions of fear or sadness than are their fellows. The orang-utan - the most solitary of our primate kin - has a version of the gene that is even less busy than that of the most socially isolated human. Whether its feeble serotonin pump has much to do with its lonely life and presumed dislike of dinner parties remains to be proved.
People with severe depression often find it hard to sense the emotions of others. Drugs that affect serotonin can help the illness - and their immediate effect, sometimes within hours of the first pill, is to improve a patient’s ability to interpret their fellow citizens’ feelings from their faces. That simple talent turns the key that restores them to society.
Nowhere is the importance of signals better seen than in children. When very young their insights are limited and self-centred, but soon they begin to understand and to respond to the moods of those around them. Darwin wrote a Biographical Sketch of an Infant, an account of child development based on his son William: ‘When 110 days old he was exceedingly amused by a pinafore being thrown over his face and then suddenly withdrawn; and so he was when I suddenly uncovered my own face and approached his. He then uttered a little noise which was an incipient laugh.’ William ‘did not spontaneously exhibit affection by overt acts until a little above a year old, namely, by kissing several times his nurse who had been absent for a short time’. By then he could tell faces apart (some of which pleased him more than others) and could copy movements. By the age of eighteen months most children can separate false movements of anger or upset made in play from real gestures and by five - school age - they send and receive information well enough to allow them to live in groups, to learn and, in time, to join society. A sense of self and a sense of other are closely related, for the younger a child is able to recognise a picture of itself the better it interacts with its fellows when it grows up.
William and his brothers and sisters were lucky for they were raised in an affectionate household. Many youngsters are less fortunate. An infant brought up in isolation or by cruel parents may never adjust to the world around it and can feel isolated for the rest of its life. The fit between childhood abuse and adult depression is well established and those taken into care because of poor parenting are at far higher than average risk of emotional problems later in life. A failure to be provided with the signals of affection that bind children to their mothers and fathers and to society as a whol
e is to blame.
A few unfortunates suffer from loneliness or despair for the opposite reason. What condemns them is not neglect by those who should provide the crucial emotional messages, but their own inability to receive and interpret them. Such children are often diagnosed as autistic. They may live in isolation and unhappiness, with an existence that can seem scarcely human at all, for children with severe autism cannot make or understand the cues needed to find a place among their peers. Their plight shows how central is the ability to express, and to understand, emotions in allowing every citizen to take part in society.
Autistic children are now treated with sympathy and concern, but once they were regarded almost as animals. To those curious about where the essence of humanity might come from, they were useful raw material for speculation. Rousseau wondered whether a youth brought up ‘wild, untamable and free’ would be safe from the corruption faced by those who undergo a normal education. He pondered an ‘impossible experiment’: to raise a newborn infant in isolation, but as he wrote, ‘by our very study of man, the knowledge of him is put out of our power’ - nobody would be so cruel as to do such a thing. Such a child might, he thought, show how the true signals of inner sentiment emerge in a creature that had never received them.