A few months ago, I went to Sweden, had an out-of-body experience and got stabbed with a knife. Sort of. The freelance life is really working out…I was there to meet Henrik Ehrsson, a neuroscientist who specialises in illusions that distort people’s sense of self. I’ve written about his work before on this blog. He can convince you that you’ve swapped bodies with a mannequin, grown a third arm, left your body or shrunk to doll-size – all of which tells us some really interesting things about how the brain works.
My feature about Ehrsson has just come out in Nature. I’m very proud of it, so do check it out. It also comes with a podcast interview with me, and a slideshow of pics that I took on the trip. Here’s the opener:
It is not every day that you are separated from your body and then stabbed in the chest with a kitchen knife.But such experiences are routine in the lab of Henrik Ehrsson, a neuroscientist at the Karolinska Institute in Stockholm, who uses illusions to probe, stretch and displace people’s sense of self. Today, using little more than a video camera, goggles and two sticks, he has convinced me that I am floating a few metres behind my own body. As I see a knife plunging towards my virtual chest, I flinch. Two electrodes on my fingers record the sweat that automatically erupts on my skin, and a nearby laptop plots my spiking fear on a graph.
Out-of-body experiences are just part of Ehrsson’s repertoire. He has convinced people that they have swapped bodies with another person, gained a third arm, shrunk to the size of a doll or grown to giant proportions. The storeroom in his lab is stuffed with mannequins of various sizes, disembodied dolls’ heads, fake hands, cameras, knives and hammers. It looks like a serial killer’s basement. “The other neuroscientists think we’re a little crazy,” Ehrsson admits.
But Ehrsson’s unorthodox apparatus amount to more than cheap trickery. They are part of his quest to understand how people come to experience a sense of self, located within their own bodies. The feeling of body ownership is so ingrained that few people ever think about it — and those scientists and philosophers who do have assumed that it was unassailable.
Finally, many thanks to my editor Helen Pearson, who really helped to knock the piece into shape.
RM had his first out-of-body experience at the age of 16. Now, at the age of 55, he has had more than he can count. They usually happen just before he falls asleep; for ten minutes, he feels like he is floating above his body, looking down on himself. If the same thing happens when he’s awake, it’s a far less tranquil story. The sense of displacement is stronger – his real body feels like a marionette, while he feels like a puppeteer. His feelings of elevation soon change into religious delusions, in which he imagines himself talking to angels and demons. Psychotic episodes follow. After four or five days, RM is hospitalised.
This has happened between 15 to 20 times, ever since RM was first diagnosed with schizophrenia at the age of 23. He hears voices, and he suffers from hallucinations and delusions. Despite these problems, he managed to hold down a job as a reporter until 2002 and more recently, he has been working in restaurants and volunteering as an archivist. Then, about a year ago, he took part in a study that seems to have changed his life.
Like it or not, the golden arches of McDonalds are one of the most easily recognised icons of the modern world. The culture they represent is one of instant gratification and saved time, of ready-made food that can be bought cheaply and eaten immediately. Many studies have looked at the effects of these foods on our waistlines, but their symbols and brands are such a pervasive part of our lives that you’d expect them to influence the way we think too.
And so they do – Chen-Bo Zhong and Sanford DeVoe have found that fast food can actually induce haste and impatience, in ways that have nothing to do with eating. They showed that subliminal exposure to fast food symbols, such as McDonalds’ golden arches, can actually increase people’s reading speed. Just thinking about these foods can boost our preferences for time-saving goods and even nudge us towards financial decisions that value immediate gains over future returns. Fast food, it seems, is very appropriately named.
Zhong and DeVoe asked 57 students to stare at the centre of a computer screen while ignoring a stream of objects flashing past in the corners. For some of the students, these flashes included the logos of McDonald’s, KFC, Subway, Taco Bell, Burger King and Wendy’s, all appearing for just 12 milliseconds. We can’t consciously recognise images that appear this quickly and, indeed, none of the students said that they saw anything other than blocks of colour.
The students were then asked to read out a 320-word description of Toronto and those who had subconsciously seen the fast food logos were faster. Even though they had no time limit, they whizzed through the text in just 70 seconds. The other students, who were shown blocks of colours in place of the logos, took a more leisurely 84 seconds.
In a world where the temptation to lie, deceive and cheat is both strong and profitable, what compels some people to choose the straight and narrow path? According to a new brain-scanning study, honest moral decisions depend more on the absence of temptation in the first place than on people wilfully resisting these lures.
Joshua Greene and Joseph Paxton and Harvard University came to this conclusion by using a technique called functional magnetic resonance imaging (fMRI) to study the brain activity of people who were given a chance to lie. The volunteers were trying to predict the outcomes of coin-flips for money and they could walk away with more cash by lying about their accuracy.
The task allowed Greene and Paxton to test two competing (and wonderfully named) explanations for honest behaviour. The first -the “Will” hypothesis – suggests that we behave morally by exerting control over the desire to cheat. The second – the “Grace” hypothesis – says that honesty is more a passive process than an active one, fuelled by an absence of temptation rather than the presence of willpower. It follows on from a growing body of psychological studies, which suggest that much of our behaviour is governed by unconscious, automatic processes.
Many studies (and several awful popular science articles) have tried to place brain-scanning technology in the role of fancy lie detectors but in almost all of these cases, people are told to lie rather than doing so spontaneously. Greene and Paxton were much more interested in what happens in a person’s brain when they make the choice to lie.
They recruited 35 people and asked them to predict the result of computerised coin-flips while sitting in an fMRI scanner. They were paid in proportion to their accuracy. In some ‘No-Opportunity trials’, they had to make their predictions beforehand, giving them no room for cheating. In other ‘Opportunity trials’, they simply had say whether they had guessed correctly after the fact, opening the door to dishonesty.
To cover up the somewhat transparent nature of the experiment, Greene and Paxton fibbed themselves. They told the recruits that they were taking part in a study of psychic ability, where the idea was that people were more clairvoyant if their predictions were private and motivated by money. Under this ruse, the very nature of the “study” meant that people had the opportunity to lie, but were expected not to.
When it comes to the human brain, even the simplest of acts can be counter-intuitive and deceptively complicated. For example, try stretching your arm.
Nerves in the limb send messages back to your brain, but the subjective experience you have of stretching isn’t due to these signals. The feeling that you willed your arm into motion, and the realisation that you moved it at all, are both the result of an area at the back of your brain called the posterior parietal cortex. This region helped to produce the intention to move, and predicted what the movement would feel like, all before you twitched a single muscle.
Michel Desmurget and a team of French neuroscientists arrived at this conclusion by stimulating the brains of seven people with electrodes, while they underwent brain surgery under local anaesthetic. When Desmurget stimulated the parietal cortex, the patients felt a strong desire to move their arms, hands, feet or lips, although they never actually did. Stronger currents cast a powerful illusion, convincing the patients that they had actually moved, even though recordings of electrical activity in their muscles said otherwise.
But when Desmurget stimulated a different region – the premotor cortex – he found the opposite effect. The patients moved their hands, arms or mouths without realising it. One of them flexed his left wrist, fingers and elbow and rotated his forearm, but was completely unaware of it. When his surgeons asked if he felt anything, he said no. Higher currents evoked stronger movements, but still the patients remained blissfully unaware that their limbs and lips were budging.
These contrasting responses tell us two important things. Firstly, they show that our feelings of free will originate (at least partially) in the parietal cortex. It’s the activity of these neurons that creates a sense that we initiate actions of our own accord. Secondly, they show that the sense of moving doesn’t depend very much on actually doing so – it depends on calculations that are made in the parietal cortex, long before the action itself begins.
Our brains are shaping our decisions long before we become consciously aware of them. That’s the conclusion of a remarkable new study which shows that patterns of activity in certain parts of our brain can predict the outcome of a decision seconds before we’re even aware that we’re making one.
It seems natural to think that we carry out actions after consciously deciding to do so. I decide to start typing and as a result, my hands move around a keyboard. But according to modern neuroscience, that feeling of free will may be an illusion. For over twenty years, experiments have suggested that, unbeknownst to us, a large amount of mental processing goes on in unconsciously before we become aware that we intend to act.
The first such study was done by Benjamin Libet in 1983. Libet asked volunteers to press a button at a time of their choice, and to remember the position of the second hand of a wristwatch when they first felt the urge to move. While this happened, Libet measured the activity of their supplementary motor area (SMA), a part of the brain involved in planning movements. Astonishingly, he found that the SMA became active about half a second before the volunteer felt a conscious desire to press the button.
The seminal experiment suggested that the brain makes decisions on a subconscious level and that people only believe that they consciously drove their actions in hindsight. The experiment seemed to put a dent in beliefs about free will and understandably, it has proved to be controversial. Some have criticised the techniques that Libet used, claiming that inaccurate measurements could explain that the small gap between brain activity and conscious awareness.
For those who were convinced by the experiment’s results, a slew of important questions remained. Is the SMA the source of the decision, or is it responding to other parts of the brain even higher up the chain of command? And is this unconscious activity a sign that the relevant areas of the brain are revving into readiness, or does it actually predict the action that is eventually taken? Now, Chong Siong Soon and colleagues from the Max Planck Institute have addressed these queries with an elegant update of Libet’s work.