Theory of Mind

Theory of mind is the ability to attribute mental states — beliefs, desires, intentions, emotions — to oneself and to others, and to use these attributions to explain and predict behaviour. It requires understanding that other people's minds represent the world in ways that may differ from one's own and from reality. A child with theory of mind understands that a person who hasn't seen an object moved will look for it where they last saw it (their false belief), not where it actually is.

In the Sally-Anne task (Baron-Cohen et al., 1985): Sally places a marble in a basket and leaves the room. Anne moves the marble to a box. The child is asked: "Where will Sally look for the marble?" A child with theory of mind answers "in the basket" — representing Sally's false belief. A child without ToM typically answers "in the box," reporting where the marble actually is rather than where Sally falsely believes it to be. Baron-Cohen et al. found that 80% of autistic children failed the task compared with about 15% of typically developing children aged 4.

The standard false belief task is typically passed around age 4 in neurotypical children. Precursors emerge earlier: joint attention (sharing attention to an object with another person) develops around 9–12 months; pretend play by 18–24 months; and understanding of desires and simple intentions by age 2–3. More demanding second-order false belief tasks ("what does A think B thinks?") are typically passed around age 6–7. Some researchers using implicit, looking-time paradigms have suggested rudimentary ToM-like processing much earlier (infants under 2), though interpretation is contested.

Baron-Cohen et al. (1985) found that most autistic children failed the Sally-Anne false belief task despite being cognitively old enough to pass. The deficit was specific to autism — not seen in children with Down syndrome (who have general cognitive delay). Baron-Cohen (1995) proposed "mindblindness" as the core feature: difficulty automatically mentalising — representing what others know, believe, and feel. This makes social interaction unpredictable and effortful. However, the picture has become more nuanced: many autistic adults pass standard false belief tasks but report social difficulties in more complex real-world situations, suggesting compensatory strategies or a distinction between explicit and implicit mentalising.