For decades, developmental psychologists have been fascinated with the question of how children develop theory of mind – in other words, how we come to understand that other people can have different types of thoughts, beliefs and knowledge to ourselves. A key milestone in this journey involves developing a notion of false belief; sometimes, the things that people believe about the world are very different from the reality of the situation, and this will have important consequences for how people act. But how do you measure something so seemingly esoteric?
The classic experiment
Beginning in 1983, a series of studies used fictional scenarios to try and assess at what age children start to get a grasp of the existence of false beliefs. Perhaps the most influential of these experiments is known as the Sally Anne task, developed by Simon Baron-Cohen, Alan Leslie and Uta Frith, then at the MRC cognitive development unit in London. In the experiment, children were presented with two dolls, Sally (who has a basket) and Anne (who has a box). Sally puts a marble in her basket, and leaves the room. While Sally is away, Anne takes the marble from the basket, and hides it in her box. Finally, Sally returns to the room, and the child is asked three questions:
- Where will Sally look for her marble? (The “belief” question)
- Where is the marble really? (The “reality” question)
- Where was the marble at the beginning? (The “memory” question)
The critical question is the belief question – if children answer this by pointing to the basket, then they have shown an appreciation that Sally’s understanding of the world doesn’t reflect the actual state of affairs. If they instead point to the box, then they fail the task, arguably because they haven’t taken into account that they possess knowledge that Sally doesn’t have access to. The reality and memory questions essentially serve as control conditions; if either of these are answered incorrectly, then it might suggest that the child didn’t quite understand what was going on.
In the original study by Baron-Cohen and colleagues, three groups of children were tested: typically developing children (aged around four), children with Down’s syndrome (aged around 11), and children with autism (aged around 12). The findings were comparable for the typically developing children and those with Down’s syndrome – in both groups, around 85% of participants correctly answered the belief question. For the children with autism, the pass rate was much lower, at 20%. For the 80% that failed the task, they consistently pointed to the actual location of the marble.
More broadly, other studies have shown that four-year-olds tend to get the idea that Sally will look in the basket, whereas three-year-olds instead point to the box. So at this early stage then, children seem to show a difficulty in understanding that other people might have different levels of knowledge to them, and will therefore behave differently to them in the same situation.
Since its publication in 1985, the Sally Anne study has spawned a huge research literature looking at how theory of mind develops in different populations at different stages. The original study was interesting, because it provided a simple and straightforward way of trying to get under the hood of a hugely complex aspect of human thinking. And perhaps given the way that seemingly fundamental concepts like truth and reality are increasingly coming under attack in a world of “alternative facts”, developing our understanding of how false beliefs arise could have profound implications for navigating a post-truth world.
Further reading
Baron-Cohen, S., Leslie, A.M., & Frith, U. (1985). Does the autistic child have a “theory of mind”? Cognition, 21, 37-46.
