I know what you're thinking

Our ability to put ourselves in another person's shoes and 'read their mind' is what makes us human. But how do we do it? Sanjida O'Connell reports

The author Henry James once wrote: "There was an extraordinary mute passage between her vision of this vision of his, his vision of her vision, and her vision of his vision of her vision." This passage in What Maisie Knew describes an essential essence of the human mind. As convoluted as James's prose is, he had deciphered what it is that makes us human; now scientists have discovered where in the brain this essential element lies.

The author Henry James once wrote: "There was an extraordinary mute passage between her vision of this vision of his, his vision of her vision, and her vision of his vision of her vision." This passage in What Maisie Knew describes an essential essence of the human mind. As convoluted as James's prose is, he had deciphered what it is that makes us human; now scientists have discovered where in the brain this essential element lies.

When James wrote about what Maisie thinks that her step-father thinks she is thinking, he was describing something called the Theory of Mind. This is "the mind's ability to think about the mind," according to Professor Simon Baron-Cohen, from the Department of Experimental Psychology at the University of Cambridge, or, as Dr Helen Gallagher, from the School of Health and Social Care, Glasgow Caledonian University, puts it: "The ability to understand other people's behaviour by recognising that they're different entities with different beliefs, desires and goals from our own."

The Theory of Mind is a fundamental skill, as Dr Gallagher explains. "Thinking about what others think is essential to our capacity to engage in complex social interactions. It underpins our ability to co-operate and empathise but also helps us to deceive and manipulate others."

The bench-mark for Theory of Mind is the false belief test, as it shows the most clear-cut use of our ability to think ourselves into another person's shoes. For example, Chris knows that Helen wants a chocolate. He also knows that the chocolates are in the cupboard but that Helen thinks they're in the drawer. Thus Chris's knowledge of Helen's desire enables him to predict that she will go to get the chocolates, but his recognition of her false belief about their location, means he knows she'll look in the drawer and not the cupboard.

Theory of Mind is a relatively new field, but researchers have taken advantage of brain-scanning techniques that have shown which parts are used to carry out specific tasks. Their results, and Dr Gallagher's own early work, have indicated that a number of areas of the brain are associated with Theory of Mind. The superior temporal sulcus (STS), for instance, plays an important role in recognising body language and identifying gaze direction (often what a person is looking at is what he or she is paying attention to or would like to have; thus eyes are a vital clue, as Shakespeare would have us believe, to the soul). Another brain region, the temporal poles, are used to recognise people, scenes and voices as well as being linked to memory. As Dr Gallagher says: "Theory of Mind contributes to our ability to lie and deceive. But in order to deceive someone, you need to be aware of what they know now, as well as what they knew in the past and what you told them, so memory plays an important part."

Other researchers, including Professor Baron-Cohen, have found that the amygdala and the orbitofrontal cortex are involved. In one study, Professor Valerie Stone, from the School of Psychology, University of Queensland, Australia, and Professor Baron-Cohen tested people who have a mild form of autism (who are unable to understand Theory of Mind) and people with brain lesions to see if they understood a faux pas. Professor Stone says a faux pas is a good way of testing Theory of Mind because it's "an unintentional insulting or hurtful comment. Understanding that one has occurred requires understanding that someone would feel bad, that the person saying it did not know some information that would have prevented them from saying it, and that the person did not intend to say something hurtful - so it tests empathy, beliefs and intentions."

One of the examples researchers used was of a woman who bought her friend a crystal bowl as a wedding present. A year later the woman accidentally smashed the bowl and, as she was apologising, her friend told her not to worry, she'd never liked it - someone had given it to her when she got married. The researchers found that both people with autism and those who had lesions to the orbitofrontal cortex did poorly on understanding what a faux pas was, indicating that this region is crucial for Theory of Mind.

In other tests, Professors Stone and Baron-Cohen found that the amygdala was used too. "I think he thinks it's a really important area," says Dr Gallagher, demonstrating Theory of Mind herself, adding, "The amygdala may be responding to emotion in a person's facial expression." In Dr Gallagher's own study, a number of brain regions were also activated. In one case Dr Gallagher told stories to volunteers that involved thinking about someone else's thoughts. For instance, a burglar breaks into a jewellery shop. As he is running away from the scene of the crime, he drops his glove in front of a policeman. The policeman picks it up and runs after him. The burglar immediately stops and gives himself up. He hadn't realised that the policeman was only returning his glove and was unaware of the theft.

But what Dr Gallagher realised was that all these studies used myriad cues - facial expressions, body language and memory as well as requiring the subject to think about the task in the past, rather than computing Theory of Mind in the present. What she wanted to do was make people think about another's thoughts without any cues from body language, facial expression or memory. Her volunteers played the game of scissors, paper, stone. Two people have to choose one of the three objects at the same time. Scissors beat paper because they can cut paper, paper beats stone because it can be wrapped round the stone, and stone beats scissors because it can crush them. The volunteers were all men and played a computerised version of the game; half of them believed that they were playing against Dr Gallagher. These men tried to guess what Dr Gallagher would do next, based on the previous choice of object. The part of the brain the men who believed they were playing against a person used was called the paracingulate cortex. "The men were quite cross that I always won," says Dr Gallagher, but, in fact, all the volunteers were playing a computer with a random output.

The paracingulate cortex, which nestles near the front of the brain, seems, according to Dr Gallagher, to be the hub of Theory of Mind. "It's an area that mediates Theory of Mind, as it integrates information to help process Theory of Mind. You don't need information from other brain regions to compute Theory of Mind but, in real life, you do draw upon all the other social cues from people," she says.

But Professor Stone says: "I don't agree at all. There are several components to Theory of Mind; such a complex multi-component, cognitive ability is unlikely to be localised in a small region of the brain. I suspect that paracingulate cortex is involved in some of the more general processes used in Theory of Mind but is not specific to Theory of Mind."

No doubt Henry James, had he been a witness, would have concentrated on the complexity of the social interactions between the scientists rather than their beliefs about where Theory of Mind resides.

Sanjida O'Connell is the author of 'Sugar: the Grass that Changed the World'; Virgin Books, £20