There’s more to your mind than your brain – your body plays a part in everything from social savvy to mathematical ability
TAKE a minute out of the hustle and bustle of your busy life and sit very still. Now, place your hands on the arms of the chair or the desk in front of you, and try to focus your attention on counting your heartbeats. Can you feel a throbbing drum roll, a slight murmur or nothing at all? How does your bladder feel – is it empty or will you need to dash for the bathroom within the next half hour? You may be surprised to learn that these bodily sensations are helping you think.
We tend to view the mind as an aloof, disembodied entity but it is becoming increasingly clear that the whole body is involved in the thinking process. Without input from your body, your mind would be unable to generate a sense of self or process emotions properly. Your body even plays a role in thinking about language and mathematics. And physiological sensations, such as those from your heart and bladder, influence such diverse personal attributes as the strength of your tendency to conform, your willpower and whether you are swayed by your intuitions or governed by rational thought.
In the past few years, discoveries about mind-body connections have overturned the long-held view of the body as a passive vehicle driven by the brain. Instead there is more of a partnership, with bodily experiences playing an active role in your mental life. “The brain cannot act independently of the body,” says Arthur Glenberg at Arizona State University in Tempe. Tune in to the body’s signals, and you can exploit this to improve your creativity, memory and self-control.
René Descartes must be turning in his grave at these findings. In his Meditations on First Philosophy, published in 1641, he famously argued that the mind and body are, in essence, two separate entities that could theoretically exist entirely independently of one another. The book sparked a fierce debate into the exact nature of the mind-body connection – a debate that continues to this day. At the centre of the modern discussion is the puzzling sensation of embodiment. The feeling that we own the flesh and blood that stretches from the tips of our toes to the crown of our head is the essence of our sense of self. As such, embodiment is central to consciousness, yet, until recently, we knew little about it.
The first hint of the answer came from an eerie illusion discovered in the late 1990s by Matthew Botvinick, then a doctoral student at Carnegie Mellon University in Pittsburgh, Pennsylvania. He had the idea that embodiment emerges from the brain’s need to integrate the information it is receiving from various senses. A Halloween party gave him the perfect opportunity to test this, when he discovered that someone had brought a rubber arm along as part of their costume. Placing the fake arm where he could see it on a table, while hiding his real arm from view, Botvinick asked an accomplice to stroke both rubber and real arms at equivalent places and in time with one another. As he suspected, in an attempt to reconcile the tactile and visual stimuli, he began to feel as if the stroking sensation was coming from the arm he could see (see video above). It was as if his brain had forgotten about the real arm and now felt it owned the fake one. He was suitably spooked by the sensation: “I was so unsettled I threw the arm across the room.”
Subsequent lab experiments confirmed the result wasn’t just the product of a hard night’s partying. Importantly, Botvinick also found that the illusion did not occur when brush strokes on the real and fake arm were out of sync, because then the brain was not receiving confused messages that it had to resolve (Nature, vol 391, p 756).
Soon, other groups saw the potential of the rubber-hand illusion for unlocking the secrets of embodiment. Brain scans taken as people fell for the trick showed that we have a crude body map in the brain’s right temporoparietal junction. When our senses provide information about our bodies, this is compared and integrated with the map in the premotor and parietal cortices (see diagram). Any mismatch must be resolved at this stage, leading to illusions such as the rubber hand. However, it is only when the integrated information reaches another area called the insular cortex that the feeling of embodiment pops into conscious awareness.
That’s not all. The insular cortex also processes our internal bodily signals, including the throb of our pulse and rumble of our gut. And it turns out that people vary greatly in how good they are at detecting these, an ability known as interoception. A team led by Manos Tsakiris at Royal Holloway, University of London, found that around a quarter of volunteers were able to count their own heartbeats with an accuracy of at least 80 per cent without taking their pulse, while another quarter had little conscious awareness of it, missing the actual number by 50 per cent or more. Intriguingly, the team also found that those who were particularly good at interoception were less susceptible to embodiment illusions, perhaps because these internal sensations override the contradictory information from their eyes (Proceedings of the Royal Society B, vol 278, p 2470). “If you have a strong sense of self from the inside, you don’t rely so much on external information like vision and touch,” says Tsakiris.
Since those pioneering experiments all kinds of related illusions have surfaced, each unveiling more about the mind-body connection and the way it moulds our thinking. Henrik Ehrsson and colleagues at the Karolinska Institute in Stockholm, Sweden, for example, recently used a set-up similar to Botvinick’s to persuade volunteers to embody plastic bodies of various sizes, including the diminutive figure of a Barbie doll. Ehrsson noticed that the subjects perceived things as being much bigger when they were under the illusion that they were just 30 centimetres tall. “When we sat next to them, they had the sense that a giant body was nearby,” he says. This suggests that our body awareness affects how we interpret the raw information hitting our eyes (PLoS One, vol 6, p 20195).
Tsakiris, meanwhile, has found that if he strokes someone’s face in sync with a random face being stroked on a screen, he can persuade them to feel as if the image is their own reflection (PLoS One, vol 3, p 4040). This illusion is particularly intriguing, since it indicates that the body’s influence might reach beyond sensory perception to determine how we relate to other people. Tsakiris believes it could explain why we warm to people who subtly copy our facial expressions and body language. He thinks that seeing a reflection of our movements in someone else may evoke a faint version of the face-swap illusion, prompting us to act towards them rather as if we are admiring ourselves in the mirror.
An experiment by Maria-Paola Paladino at the University of Trento in Italy lends some support to this idea. She asked volunteers experiencing the face-swap illusion to rate their own personality, and to guess at the personality of the person on the screen in front of them. They considered themselves to be strikingly similar to the person on the screen. In a subsequent perceptual test, they were asked to estimate the number of letters flashed on a screen, while being told how the virtual person had answered. They were more likely to chose a figure around that answer than were people who had not been subjected to the illusion (Psychological Science, vol 21, p 1202). Since people who are naturally sensitive to their internal signals are not as easily hoodwinked by body illusions, they may be less affected by this kind of social manipulation, and less empathic as a result.
If the simple feeling of the heart beating in our chest is somehow connected to our subconscious reactions to a person, how might the body’s myriad other processes be shaping our thinking? That is exactly what researchers studying “embodied cognition” would like to know. Running against Descartes’s philosophy, this school of thought maintains that many, if not all, aspects of our mental lives are inextricably linked to the experiences of our flesh and blood.
Emotional experience is perhaps the best-studied area of embodied cognition. As a simple example, you may think that you smile because you are happy, but in fact happy feelings arise in a large part from the physical sensation of smiling (Journal of Personality and Social Psychology, vol 54, p 768). Even very subtle facial expressions appear to be essential for us to process emotions. In one particularly elegant example, Glenberg’s team showed that people whose frown muscles had been frozen with botox took longer to read sad or angry sentences than they did before receiving the treatment (Psychological Science, vol 21, p 895). Emotions are also linked to physical sensations. We tend to feel colder when we feel lonely, for example, and we associate warmth with friendliness and inclusion.
Such findings suggest that people who are in tune with their bodies are more sensitive to their own feelings. The jury is out on this one, though the fact that the same brain region – the insular cortex – handles both interoception and emotional processing supports the idea (Nature Neuroscience, vol 7, p 189). There is also evidence that you can tap into this connection to improve your intuitive decision-making (see “How to follow your heart”).
Touchy-feely emotions are one thing, but embodied cognition might stretch even further to abstract thought processes. Mathematical thinking, for example, seems somehow to piggyback on our experience of movement and space. When people are asked to think of random numbers, they are more likely to come up with smaller ones if they look down and to the left, and bigger ones if they look up and to the right (New Scientist, 27 March 2010, p 8). Other studies show that language is also deeply embodied. Every time we hear a word, the brain seems to simulate the actions associated with its meaning. When someone says the word “climb”, for example, it activates the same neural regions that trigger our muscles to pull our weight up a tree. What’s more, appropriate hand gestures can help our understanding of these words (New Scientist, 8 April 2000, p 30).
The field of embodied cognition is only just beginning to blossom, though it has had a relatively long history. Many questions remain, including where these mind-body associations come from. Are they innate or learned in infancy? “When we’re cuddled up with mum, we might learn to associate warmth with feelings of social closeness,” says Glenberg. But the link could be hardwired. It also remains to be seen exactly how much our mental and physical lives intertwine. “My personal belief is that all cognition is embodied,” says Glenberg, “and the evidence is slowly inching towards this view.”
None of this detracts from the many exciting applications of mind-body research. Tsakiris is looking at the clinical uses of illusions. A version of the rubber-hand illusion might help the brain to accept a prosthetic limb, while something akin to the face illusion could ease the rehabilitation of anyone receiving a face transplant. Face-swap illusions could also be used to help us better understand empathy and prejudice. Experiments where white and black faces are interchanged, for example, could give an insight into implicit biases. On a more frivolous note, body illusion techniques could help players embody virtual avatars in immersive video games.
Education should benefit, too. Glenberg has found that young children learn much more quickly, and understand more, if they are encouraged to play-act what they are reading. Their memory of the words seems to attach itself to the sensory experiences involved, he thinks. Susan Goldin-Meadow at the University of Chicago noticed something very similar in children learning simple equations. Those encouraged to gesture tended to understand the material more quickly and remember what they had learned for longer (Language and Cognition, vol 2, p 1). The mechanism remains murky, though it is clear that the movements somehow activate an implicit understanding of the material.
You might be able to make use of these discoveries in your own life. Whether you want to increase your willpower, creativity or memory, there are numerous ways to exploit the mind-body connection for your own benefit (see “Creative posturing” and “Flexing your willpower”). The effects may be moderate, but sometimes that’s all you need. With your body helping you to think more effectively, you never know what you might achieve.
Truman Capote once described himself as a “horizontal author”, saying “I can’t think unless I’m lying down, either in bed or stretched on a couch and with a cigarette and coffee handy.” Vladimir Nabokov was a similarly supine writer.
They might have had a point. Darren Lipnicki and Don Byrne at the Australian National University in Canberra have found that people solved anagrams in about 10 per cent less time when lying down compared with standing (Cognitive Brain Research, vol 24, p 719). The mechanism is fairly simple. Stress is well known to be the enemy of creativity, and we feel more relaxed on our backs than on our feet.
If you can’t persuade your boss to buy you a chaise longue for the office, there are some more discreet ways to get those creative juices flowing. For instance, Joël Cretenet and Vincent Dru from Paris West University Nanterre La Défense suggest that you extend your left arm out in front of you or bend your right arm at the elbow, so you resemble Auguste Rodin’s iconic statue The Thinker. Volunteers who made these moves performed much better on a creative thinking task, in which they had to find innovative uses for an everyday object, such as a brick (Journal of Experimental Psychology: General, vol 138, p 201). The explanation is complicated, but it seems the movements are tied to our instincts to approach or distance ourselves from a situation. This helps broaden our outlook on the problem, which is known to be crucial for flexible thinking.
Even simple eye movements left and right across your field of vision can help you to think more laterally. It is thought that this temporarily encourages communication between the right and left hemispheres of the brain, which boosts creativity (Brain and Cognition, vol 71, p 204).
Flexing your willpower
Before you make your next important decision, try to hold off from visiting the bathroom for a few hours, says Mirjam Tuk at the University of Twente in the Netherlands. “It could give you a little more self-control.” She’s not joking.
Tuk’s discovery came after she read that just one neural circuit determines our self-control in lots of different areas. She wondered whether flexing willpower in one domain might therefore bolster resolve in another. Just then, nature started to call, suggesting the perfect way to test her idea. In her subsequent experiment, Tuk asked half of her volunteers to drink a few glasses of flavoured water, under the ruse that they were taking a taste test; the rest just took a sip of each sample. They waited a while before trying numerous tasks, including a classic test of self-control – considering whether they would prefer to receive a small amount of money now, or a larger sum at a later date. The subjects who had downed the drinks were more likely to choose to wait (Psychological Science, in press, DOI: 10.1177/0956797611404901).
Fortunately, a bursting bladder is not the only way your body can help to increase your willpower. Walking backwards, or tensing your muscles, can strengthen your resolve, too. Folding your arms, meanwhile, seems to make you more persistent at a task in hand (European Journal of Social Psychology, vol 38, p 449).
How to follow your heart
We often use metaphors involving the body to describe the process of intuition – we talk about going with our “gut instincts” or “following our hearts”. Perhaps we should take these phrases more literally. Barnaby Dunn at the Medical Research Council Cognition and Brain Sciences Unit in Cambridge, UK, and colleagues have found that people who take notice of subtle physiological changes tend to be more intuitive.
The team first asked volunteers to sit quietly and try to count out their heartbeats without feeling for their pulse. All the while, an ECG machine took an accurate measurement. Comparing these two results gives a good indication of a person’s “interoception”, their ability to read their body’s internal signals. Then, to test their intuition, the participants played a simple computer game. The computer offered them four decks of cards and on each round they had to guess which deck would present a card of a certain colour. Unbeknownst to the players, the set-up was rigged – two of the decks were always slightly more likely to have the winning cards than the other two. The results were surprising. Those with the best interoception tended to be either the best, or the worst, at this card game. Those who were bad at reading their body’s signals came right in the middle (Psychological Science, vol 21, p 1835).
Why could this be? Dunn suspects it is down to the way we process our emotions. In another experiment, he asked the same subjects to rate their emotional reactions as they looked at a series of emotive pictures. The better they were at interoception, the more these ratings correlated with physiological change, such as a shift in heart rate. Dunn suggests that having a hunch might create a flicker of excitement or interest that is reflected in subtle changes in physiology. Since people with good interoception are more sensitive to these signals, their perception of the hunch is stronger, making it more likely that they will act on it. “Their bodies are driving what they decide,” he says. That doesn’t mean the hunch is right, though – which would explain why these people did the best, and worst, of the group.
If you would like to tap into the signals that your subconscious mind is sending your body, you might want to take up meditation. Jocelyn Sze and colleagues at the University of California, Berkeley, have found that meditating improves bodily awareness and results in the same kind of link between physiological and emotional reactions that Dunn found to be crucial for intuition (Emotion, vol 10, p 803).
David Robson is a features editor at New Scientist
Your clever body: Thinking from head to toe – life – 21 October 2011 – New Scientist.