Are You Thinking What I’m Thinking You’re Thinking?

For this trick you will need: two children, aged three and four respectively; mini felt-tip pens; an empty tube of Smarties. Put the pens into the Smarties tube, close the lid, and find the four year-old.

‘What do you think will be inside this tube?’ 


‘Let’s look.’ (Show the child the inside of the tube, and watch their disappointed face as they realise there are no Smarties to be had).

‘Oh. Pens.’

‘Let’s close the tube again. If I showed this to your friend, what do you think they would think was inside the tube?’


Obvious? Now try again, this time with the three year-old. Same tube, same disappointment. But when you ask them what their friend would expect to be inside the tube, they will invariably answer


To uncover the secret behind this developmental magic trick, it’s important to understand ‘theory of mind’. A good first definition is Ori Friedman and Alan Leslie’s: they explain it as ‘the ability to recognise and reason about people’s mental states’. In other words, theory of mind allows us to understand that other people have independent thoughts, and to infer what these thoughts may be. Let’s first consider the four-year-old. Anyone encountering a rattling tube emblazoned with ‘Smarties’ on the outside will expect it to contain chocolate. But the child knows that there are actually pens inside the tube, and in order to pass the test they have to recognise that different people have different thoughts: not all children know what they know. The three-year-old is not so capable. They expect Smarties at the start, but think their friends will expect pens at the end. This mistake is rooted in their inability to use theory of mind. Because they know that there are pens in the tube, they reason that everyone knows. This failure to understand others’ false-belief is considered evidence that theory of mind has not yet developed: tasks such as this one were first designed in the early eighties by Heinz Wimmer and Joseph Perner for exactly this purpose.

The importance of theory of mind reaches far beyond confectionery. It is crucial for social success, largely because of its role in empathy: in order to relate to other people, we must first be able to recognise their thoughts and emotions. Of course, just because we have theory of mind, it doesn’t mean we always use it well. Incredulity at another’s ignorance or different opinion is not worlds apart from a three-year-old insisting everyone knows there are pens inside a Smarties tube. We easily forget former ignorance, and overestimate how much our own thoughts and emotions are visible to others. It is nonetheless true that we use theory of mind constantly and automatically, and that without it human interaction would be fundamentally altered.

Theory of mind is not just significant for its role in social cohesion. It may clarify and confound in real life, but it is also the backbone of much literature, theatre and film, and its relationship with fiction is worth exploring. As reader or audience, we often find ourselves willing participants in theory of mind games, albeit far from a research lab. The psychologist Martin Doherty opens his book on social cognition with an extract from Jane Austen’s Pride and Prejudice, as evidence of our natural mentalising ability:  

‘Elizabeth could not help observing, as she turned over some music books that lay on the instrument, how frequently Mr. Darcy’s eyes were fixed on her […] that he should look at her because he disliked her, was still more strange.’

This extract is an odd showcase of theory of mind aptitude: Lizzie gets it wrong (hence the titular prejudice). Austen’s novel repeatedly turns to such mistakes, for example in the Bennet family’s failure to recognize Wickham’s true intentions. But it does more than take theory of mind as a theme: it also demands some fairly complicated mental state reasoning from the reader. When reading these words, we are thinking about what Darcy is thinking, and what Lizzie is thinking Darcy is thinking (and, perhaps, what Austen is thinking about what Lizzie is thinking Darcy is thinking). In psychological terms, this is second-order false-belief reasoning, which we are first able to carry out at around seven years old.

In the world of fiction, it’s not just 19th century novels that play around with theory of mind. Most of us will remember our childhood selves shouting gleefully, high on sugar and audience participation, ‘he’s behind you!’ at a Yule-time panto.

‘Oh no he isn’t!’

‘Oh yes he is!’

The delight in this exchange is rooted in the glorious age where theory of mind and suspension of disbelief meet: a child who sees that the hero doesn’t know where the villain is (while the child does), and can accept that this is really true (rather than carping that the actor knows exactly where the villain is because they’ve been doing the same sketch twice a day for the last month). The balance may have tipped toward cynicism by adulthood, but the power felt by the child who realises they know something the hero doesn’t is immense, and generated entirely by their theory of mind. 

One man’s pantomime tedium is another’s dramatic irony. A more grown-up instance can be found at the end of Romeo and Juliet, when Romeo finds an apparently dead Juliet and kills himself seconds before she wakes up from a rather implausible coma. We know she’s not dead; we might be shouting it at the stage if we weren’t hushed by decorum. Shakespeare makes it even worse for us, as Romeo himself observes Juliet’s flushed features even as he despairs in her death: ‘beauty’s ensign yet / Is crimson in thy lips and in thy cheeks / And death’s pale flag is not advanced there’. ‘Of course it’s not’, we cry inwardly, ‘she’s not dead.’ Dramatic irony indeed, and entirely reliant on our theory of mind: we understand that despite our knowledge, and despite the evidence before him, Romeo really thinks Juliet’s dead. Worse, his false-belief will kill him. This raises another interesting way in which literature plays with theory of mind: it allows false-belief to persist longer than we would ever let it in real life.

Theory of mind also engages us in literature when we find ourselves in a position of ignorance rather than knowledge. Take crime fiction. Agatha Christie ensures that we spend her novels in a dance of suspicion, distrusting everything everyone says and looking for evidence of their true thoughts. Writers love to mislead, especially through unreliable narrators. We think through their thoughts, missing truths that seem blindingly obvious when they eventually emerge (consider Fight Club). Different characters present us with incompatible realities (such as in the novel Waterland, or Infinite Jest), or try to make justifiable a way of thinking that is socially unacceptable, and alien to our own (Humbert Humbert, in Lolita). Theory of mind involves constant reasoning about someone’s mental state, but first person narration hurls us directly into a mind, a dubious luxury we’re never afforded in reality.

Nothing here is novel. We know what dramatic irony is, have heard many times of the unreliable narrator. But it’s appealing to think how far theory of mind is embedded in fiction: in its plots, and also in our reading and response. Even, really, in how fiction is used to make sense of theory of mind: so many of the ways psychologists and philosophers look at it involve story-telling. As an example, let’s return to false-belief tasks. A popular one involves the tale of Sally and Anne, told through cartoons, puppets or narration. Sally puts her marble in a basket for safe-keeping, and leaves the room. Anne, left behind, takes the marble out of the basket and puts it in a box. The child is asked where Sally will look for her marble when she comes back into the room. It takes theory of mind to answer ‘in the basket’, just as it takes theory of mind to understand that Romeo thinks Juliet is dead. Both characters remind us that when people are ‘off-stage’ they carry around with them beliefs that they have acquired in the past, which may or may not be true, and which may or may not be the same as our own.

What does all this mean for people who don’t pass the Smarties task, or who never fully acquire theory of mind? I wonder what the three-year-olds are thinking at the panto.