by John Coates
In the end Cannon’s arguments carried the day, and James’s theory retreated from the field of emotional studies, living on in the nether world of interesting but disproved ideas. Yet in the 1970s and 80s that began to change. Many scientists took a renewed interest in feedback between body and brain, and decided it was time to take another look at James’s theory.
What they found was that Cannon had formulated his criticisms by focusing exclusively on what can be called the visceral nervous system, the network of nerve fibres controlling your heart, lungs, arteries, gut, bladder, sweat glands and so on. But the visceral nervous system is just one of many lines of communication operating between body and brain. Indeed, it is not even the whole of the nervous system, for in addition to the nerves connecting brain to visceral organs there is the nervous system connecting brain to skeletal muscle, and this system employs signals that move at lightning speeds. Recent research has found that signals from the body do travel fast enough to generate our high-speed emotional life, and are complex enough to generate its richness. Let us look at these two points in turn.
MUSCLES AND OUR FIRST RESPONSE
When the body wants to send a signal at high speed it uses electrical signals rather than blood-borne chemical ones like hormones. But nerve fibres vary dramatically in their speed of transmission, so the body and brain choose carefully the fibres they entrust with a message. The fibres of the nervous system that connect visceral organs to brain are relatively slow, carrying their signals at speeds ranging from 5 to 30 metres per second, with some ambling along at a mere one metre per second. However, the muscular nervous system is made up of a different class of fibre altogether, and these carry signals at close to 120 metres per second. If we were to compare our body’s wiring to the internet, then the visceral nervous system constitutes a 56k modem and the muscular nervous system its broadband, the closest thing we have to instant messaging. This feature of our bodies makes perfect sense, for it is the speed of movement during emergencies that keeps us alive.
It also turns out that our muscles play an intimate role in our emotional expressions. When we are angry or sad or elated our posture changes, and muscles in one part of our body tense while others relax. The muscular nervous system, moreover, is fast enough to keep up with, even to cause, our fluctuating emotional feelings.
One set of muscles in particular has been found to play a central role in our emotional lives – the facial muscles. Some of the most exciting work on emotions and body–brain feedback has involved studying facial expressions, in particular a class called micro-expressions. These were discovered during the 1960s by William Condon at the University of Pittsburgh, among others, when he studied slow-motion film of patients undergoing psychotherapy. Condon was astonished to find facial displays of anger, disgust, fear and other emotions flicker into life and then vanish, all within the space of 40 milliseconds – that is, a mere twenty-fifth of a second. These expressions come and go so quickly we are not even aware that we have made them. But they carry a load of meaning. Their study was later taken up by Paul Ekman, a psychologist at the University of California, who began training police and security services to spot these micro-expressions as a new and reliable method of lie detection.
Faces are objects of unique significance to us, and to many other mammals as well. It is largely through faces that we learn of other people’s intentions, and they ours. When we are angry we broadcast our threat, and when sad our need for reassurance. When we encounter a person we usually begin by examining their face, either directly or surreptitiously, while they do the same to us. The result is a silent exchange in which we discern if this person is friend or foe, if we trust or distrust them; and after a moment or two the exchange may settle into a stable interpretation on both sides – we like each other. We are often only dimly aware of the changing weather on our faces as we shift from interpretation to interpretation of the person in front of us. But we also try to fool people by disguising our true feelings with the mask of another emotion, as do people looking back at us. A salesman may smile winningly at us but feel nothing but contempt.
Micro-expressions play a key role in maintaining a line of truth in this game of facial spy and counter-spy. The salesman’s micro-expression may betray his duplicity. We have little control over micro-expressions, so in many ways they remain a true gauge of our real feelings and intentions. Since mistaking foe for friend can be fatal, our brains have been built to process information coming from faces faster than from pretty well any other object in the world. Micro-expressions break the surface of our faces, transmit their signal, and then submerge just as quickly, all within 40 milliseconds; but an observer can register these signals in as little as 30 milliseconds, far faster than their conscious awareness. These extraordinary speeds mean we could potentially have an entire conversation, with several rounds of micro-expression and response, within the space of a single second, and all without any awareness it has taken place. We may merely walk away from a brief encounter with a stranger nagged by a vague uneasiness.
The speed of our muscular reactions in general, and the almost incredible speeds of facial expressions in particular, have led many researchers to venture what has been called the ‘facial feedback theory of emotions’, according to which the purpose of facial expressions is not so much to express feelings, as to generate them. This new theory echoes that of James: we act first, feel later. If this theory is true – and a great deal of research now suggests it is – it raises a number of intriguing questions. For example, do people with very expressive faces – people who have been delightfully called ‘facial athletes’ – experience a richer emotional life? Are the tight-lipped Brits emotionally handicapped? Hard to say. It is possible that people with more labile faces simply become habituated to their facial antics, and that a poker-faced Brit might succumb to an outwardly unseen emotional torrent caused by little more than a twitch of the mouth or a furtive glance. On the other hand, people who inject botox into their cheeks, foreheads and eye creases, thereby anaesthetising their facial muscles, may be dampening their emotional and indeed their cognitive reactions. Ironically, it is often movie actors who do so, yet if there is any truth to the theory of Method acting, according to which you should conjure up a real emotion rather than artfully fake it, then these actors may be killing their very talent.
Robert Levenson and Paul Ekman, two psychologists working on emotional display, have conducted a series of fun experiments to demonstrate how feedback from facial expressions alone can bring about a range of emotional feelings. They instructed participants to flex this muscle or that in their faces, relax another muscle, or to hold a pencil at the back of their teeth. While following these instructions the participants would, without knowing it, compose an emotional face, say one of happiness or sadness. After this purely physical exercise they were tested for mood. Levenson and Ekman found that by moving their facial muscles alone, without any emotive input, the subjects had come to feel the mood portrayed on their faces.
Extraordinary research. In fact, just as William James had predicted. He too recognised that muscles can communicate an emotional feeling to the brain. Even when our muscles appear outwardly unchanged, he wrote, ‘their inward tension alters to suit each varying mood, and is felt as a difference of tone or of strain. In depression the flexors tend to prevail; in elation or belligerent excitement the extensors take the lead.’
YOUR GUT IS TELLING YOU SOMETHING
Our body, through its muscles, can thus transmit information back to the brain fast enough not only to keep up with our emotional life but also to generate it. Furthermore, our body can compose messages that are complex enough to produce the full range of our emotions. It does so by drawing on a wide palette of signals, electrical ones sent by muscles and by our visceral organs, and hormonal ones carried by the blood. Contrary to Cannon’s view, our body has so many different signals at its disposal that together they can easily compose messages with all the subtlety of a pian
o keyboard, and some with the speed of a radio transmission.
The various electrical and chemical systems carrying these signals are brought online in sequential order as a challenging event unfolds. Our muscles, especially our facial muscles, kick in quickly and unreflectively, in a matter of milliseconds. Shortly thereafter the visceral nervous system, operating on the order of milliseconds to seconds, calls into action the tissues and organs, such as lungs, liver, adrenal glands, that will support our muscles during the crisis. Moments after these two electrical systems have been brought online our chemical systems begin to switch on. Fast-acting hormones like adrenalin, released in seconds to minutes, flood into the blood and unpack energy stores for immediate use. Finally, if a challenge persists, then our steroid hormones take charge, and over the course of hours, even days, they prepare our bodies for a change of life. At this point our bodies retool, girding for attack or hunkering down for a siege. Each of these staggered physical changes is reported back to the brain, where it alters our emotions, moods, memories and thoughts. To see in a highly simplified way how these feedback loops work, let us watch Gwen, the trader sitting next to Martin, deal with a scare.
Gwen, a former college tennis star with a brief stint on the professional circuit (her best year took her to the last 16 at the Australian Open), now trades five-year Treasuries. She has a solid track record at making money, but for the past month or so she has been in a slump. Normally that is no big deal – all traders go through periods when they do not make any money. Nonetheless, no trader feels comfortable at these times. There is a saying on Wall Street: you’re only as good as your last trade. Well, shortly after the DuPont trade Gwen follows Martin down the aisle to the coffee room, and on the way she catches a glimpse of Ash, the floor manager, staring at her. His facial expression broadcasts a complex message. It is almost a dispassionate gaze, but there is no denying a hint of hostility in it; and there is more, a trace of pity (why does he feel sorry for her?) and maybe disgust (the sort people feel, probably as a rationalisation, once they have decided to fire you). Gwen registers the look in a matter of milliseconds, and automatically responds with a micro-expression of shock, alarm. Muscles throughout her body tighten, straightening her posture, craning her neck. In a threatening situation such as this one, Gwen’s muscular nervous system reacts first, setting off warning bells, preparing her for quick action.
As she becomes aware of Ash’s glare, and her own tensed body, another set of messages starts to arrive, these from her visceral nervous system. Operating on the order of milliseconds to seconds, the visceral nervous system calls into action the tissues and organs that will support Gwen’s muscles during this crisis – if there is one – providing them with fuel, oxygen, cooling, exhaust removal and so on; and, with a slight delay, it floods her arteries with adrenalin. This is the fabled fight-or-flight response, a bodywide preparation for a physical emergency, involving increased breathing, heart rate and sweating, dilated pupils, suppressed digestion, and so on. The fight-or-flight nervous system first prepares Gwen’s body for action and then, by means of nerves in the spinal cord, reports her state of arousal to the brain. This information slants her perception of the world. She sees Ash’s face, registers its look, and the disturbing signals from her body suggest that something is not right. Why is he looking at me like that?
Another part of her visceral nervous system, what is called the ‘rest-and-digest’ system, brings in equally valuable information, especially from her gut, perhaps gut feelings themselves. Our visceral nervous system is composed of two branches: the fight-or-flight system and the rest-and-digest system. The fight-or-flight system is brought online in times of emergency, but once the emergency passes our body needs to settle down, rest, and basically get life back to normal. It is at these times that the rest-and-digest system takes over, damping down arousal in our bodies. The fight-or-flight nerves thus work largely (but not always, as we will see in a later chapter) in opposition to those of the rest-and-digest system, the two nervous systems alternating their activities, one speeding us up, the other slowing us down. Importantly, though, both carry information back to the brain and affect our thoughts, emotions, moods.
The main nerve in the rest-and-digest nervous system is the vagus, a large and powerful nerve that exerts a calming influence on the many tissues and organs it touches. The word ‘vagus’ (pronounced like Vegas) is Greek for wanderer, and wander this nerve does. It emerges from the brain stem and heads down into the abdomen. In the course of its long travels it visits the voicebox, then the heart, lungs, liver and pancreas, finally terminating in the gut (fig. 6). Because of its extensive connections, this curious nerve can modulate our tone of voice, slow our breathing and heart rate, and in the stomach control the early stages of digestion. What is more, the region of the brain stem where the vagus originates is also the one that regulates our facial muscles, and this allows our facial expressions to synchronise with our heart rate and the state of our gut. By linking facial expression, voice, lungs, heart and stomach, the vagus plays a central role in our emotional lives.
It also brings messages back to the brain: almost 80 per cent of the vagus nerve’s fibres (the vagus is a cable composed of thousands of fibres) carry information from body to brain. Most of this returning information comes from the gut, so one may naturally ask, do gut feelings really come from the gut? The quick answer is yes, or least some of them do. Not all, though. Interoceptive information streams into the brain from every tissue in the body, not just the gut. Nonetheless, the gut holds a special place in our physiology because, remarkably, it has its own ‘brain’.
Fig. 6. The vagus nerve and the enteric nervous system. The vagus nerve, the main nerve in the rest-and-digest nervous system, links the brain stem, voicebox, lungs, heart, pancreas and gut. Eighty per cent of its fibres carry information back to the brain, mostly from the heart and gut. The enteric nervous system, often called the second brain, is an independent nervous system controlling digestion. The brain in the gut and the brain in the head communicate and cooperate (and occasionally disagree) largely by means of the vagus nerve.
The gut is under the command of what is called the enteric nervous system (fig. 6), which controls the movement and digestion of nutrients as they pass through the stomach and intestines. Unlike other nerves in the body, this nervous system can act independently of the brain, and is one of the only systems that will continue to function even if all connection to the brain is severed. It contains approximately100 million neurons, more than are found in the spinal cord, and produces the same neurotransmitters as the brain. The enteric nervous system has been aptly termed by Michael Gershon ‘ the Second Brain’. And it is the vagus nerve that links our two brains, acting much like a hotline between two superpowers.
Through its control of digestive acids and enzymes, the enteric nervous system decomposes food until its constituent molecules can be absorbed into the body. I say ‘into the body’ because the digestive system, technically speaking, is not inside the body. The cavity inside the mouth, the oesophagus, stomach, intestines and colon remain on the outside of our body, constituting, in the words of Gershon, ‘ a tunnel that permits the exterior to run right through us’. The gut also powers the caterpillar-like undulations in the intestinal tube that inch food and waste forward, or rather backward. In fact it was the discovery of these undulations that led to the further discovery of the enteric nervous system. In 1917, Ulrich Trendelenburg, a German physiologist, removed a section of intestines from a guinea pig, severing all connection to the brain. When he blew into this section he was amazed to find the air blowing right back. This was not the sort of blowback you would get if you blew into a balloon and it squeezed the air back out. This was different. After a moment’s delay the intestinal section contracted and puffed a light gust of air right back at Trendelenburg, like some gentle creature playing a simple game. At that point it dawned on Trendelenburg that what he was dealing with was an independent nervous system.
The brain and the enteric nervous system, being connected by the vagus, send messages back and forth, affecting their respective decisions. Conditions in one brain may show up as symptoms in the other. For instance, when stressed, the brain in our head may inform the brain in our gut of an impending threat and advise it to stop digesting, such digestion representing a needless drain on energy. To take further examples, patients with Alzheimer’s often suffer constipation, as do people addicted to opiates; while patients on anti-depressants often experience diarrhoea. Information may also flow the other way, with events in the gut causing changes in the brain. For example, people suffering from Crohn’s disease, a form of inflammatory bowel disease, are more easily aroused by emotional stimuli. Furthermore, hormones secreted in the gut during feeding can enhance the formation of memories, the evolutionary rationale being, I suppose, that if you have eaten some food, then your gut hormones instruct your brain to remember where you found it. Of course, the effects of eating can also be highly soothing: a good meal can prove more than a mere gustatory treat: it can settle the body and calm the brain and suffuse us with a profound sense of well-being. In short, neural activity in our head can affect our digestion; neural activity in our gut can affect our mood and thoughts.
Gwen feels her stomach knot, her breathing speed up, her heart pound a bit harder, and these feelings, funnelled into the brain by the vagus, slant her interpretation of Ash’s glowering look. She accordingly experiences a moment of fear. But fortunately, not for long. Ash breaks off his look and turns away. Gwen thinks through the encounter and tells herself not to be so silly – he was probably looking straight through her, thinking of something else, maybe a bad position on the mortgage desk, maybe his all-too-public marital problems. She shakes off her worries, her body begins to settle, and she continues to the coffee room, not giving the incident another thought.