Theory of Mind: What It Is, the Sally-Anne Test and When It Develops

By the IQ Revealed Team · Updated October 27, 2026

Theory of mind is the ability to understand that other people have their own beliefs, desires, intentions and feelings, which can be different from yours and different from the facts. It is what lets you predict that a friend will look for her keys where she left them, not where someone moved them while she was out. Children usually pass the classic test of it, the false-belief task, between about three and five. In adults it is measured with harder tasks, and those scores overlap in part with verbal ability.

Theory of mind at a glance

What it is: understanding that others have minds of their own, and using that to explain and predict behaviour.
Where the term comes from: a 1978 paper by David Premack and Guy Woodruff that asked whether chimpanzees have one.
The classic test: the false-belief task, such as the Sally-Anne test.
When children pass it: most fail at three and pass by five, across countries.
Adult tests: harder tasks such as the Reading the Mind in the Eyes test, which also draws on vocabulary.
Autism: the old claim of a missing theory of mind is now strongly contested.

What theory of mind means

We cannot see what anyone else is thinking. We infer it from what they say, what they do and what they could have seen or heard. Psychologists call this capacity a “theory” of mind for that reason: it works like a theory, a set of working assumptions that lets us explain behaviour (“she is looking in the drawer because she thinks her keys are there”) and predict it.

The phrase was introduced by primatologists David Premack and Guy Woodruff in a 1978 paper asking whether chimpanzees have a theory of mind. Researchers often distinguish two sides of it: cognitive theory of mind, understanding what someone knows, believes or intends, and affective theory of mind, understanding what they feel. It overlaps with, but is not the same as, empathy: you can work out what someone believes without sharing their feelings. Our article on interpersonal intelligence covers the broader idea of skill with other people, and metacognition is the same kind of thinking turned on your own mind.

The false-belief test

The hardest thing to show is that someone understands a belief as a belief, rather than simply knowing where things are. The solution, developed by Heinz Wimmer and Josef Perner in 1983, is to test whether a child can predict the behaviour of someone whose belief is wrong. In their story, a boy called Maxi puts chocolate in one cupboard and goes out; while he is away, it is moved to another. Where will Maxi look for it?

The best-known version is the Sally-Anne test, used by Simon Baron-Cohen, Alan Leslie and Uta Frith in 1985:

Sally puts her marble in her basket and leaves the room.
While she is away, Anne moves the marble into her own box.
Sally comes back. Where will she look for her marble?

A child who answers “the box” is reporting where the marble really is. A child who answers “the basket” understands that Sally holds a belief that is now false and will act on it. Many three-year-olds point to the box; most five-year-olds say the basket.

When theory of mind develops

Henry Wellman, David Cross and Julanne Watson pooled 178 studies of false-belief tasks. Children went from below-chance to above-chance performance during the preschool years, and that pattern was consistent across countries and across versions of the task. A model with age, country and four features of the task explained 55% of the differences in performance between studies.

False belief is not the first step. Wellman and David Liu gave 75 children aged roughly three to six a set of seven tasks and found that they passed them in a consistent order: most children who passed a later task had also passed the earlier ones. Understanding that people want different things comes before understanding that they believe different things, then that people who have not seen something do not know it, then false belief, and only later that people can feel one emotion while showing another.

Spoken tests may still underestimate young children. Kristine Onishi and Renée Baillargeon used a task with no questions at all, measuring how long 15-month-old infants looked at an actor’s search, and found results consistent with the infants expecting the actor to act on her belief. How to reconcile these infant findings with the preschool results is still debated. For the wider picture of how children’s thinking develops, see Piaget’s stages of cognitive development.

How theory of mind is measured in adults

Almost every adult passes a simple false-belief task, so adult tests have to be harder. Common examples are stories about a social blunder (a faux pas) and the Reading the Mind in the Eyes test, in which people look at photographs of the eye region of faces and choose which of four words best describes what the person is thinking or feeling.

Baron-Cohen and colleagues revised the Eyes test in 2001 to fix psychometric problems with the first version. In their study it distinguished 15 adults with an Asperger or high-functioning autism diagnosis from 239 comparison adults, and scores were inversely related to the Autism Spectrum Quotient, a questionnaire about autistic traits. Free online versions of the Eyes test circulate widely; a score from an unsupervised online version is not a diagnosis of anything.

Theory of mind and IQ

Because this is an intelligence site, the obvious question is whether theory of mind is just another part of IQ. The honest answer is: partly related, but not the same thing.

A 2019 meta-analysis of 18 studies by Inmaculada Peñuelas-Calvo and colleagues found that, in comparison groups, performance on the Eyes test depended on full-scale IQ, on verbal IQ and on age. In autistic groups the pattern differed: Eyes scores were negatively correlated with performance IQ, which the authors read as a sign that the two groups approached the test differently. One plain reason for the link with verbal IQ is that the test is made of words: picking between labels such as “contemplative” and “suspicious” needs a large emotion vocabulary.

So a theory-of-mind score partly reflects language, and an IQ score says little about how well someone reads people in real life. Our comparison of EQ vs IQ looks at the same question from the emotional-intelligence side, and linguistic intelligence covers the verbal abilities involved.

Theory of mind and autism

The 1985 Sally-Anne study proposed that autistic children lack a theory of mind, and the idea, sometimes called “mindblindness”, became one of the best-known claims in psychology. It is now strongly contested.

In a 2019 review, Morton Ann Gernsbacher and Melanie Yergeau set out evidence that autistic people are not uniquely, let alone universally, impaired on theory-of-mind tasks; highlighted original findings that failed to replicate; documented that the various theory-of-mind tasks often do not relate to one another or to real social interaction; and concluded that the claim is empirically questionable and harmful. Damian Milton’s double empathy problem offers a different framing: when autistic and non-autistic people misunderstand each other, the difficulty runs in both directions rather than sitting inside the autistic person.

None of this means social communication differences are imaginary; they are part of how autism is described. It means a single laboratory task is a weak basis for saying what any person can or cannot understand about others. Questions about autism in a particular person are for a qualified professional who has assessed them.

Can theory of mind be improved?

In 2013 David Kidd and Emanuele Castano reported five experiments in which reading a passage of literary fiction, rather than popular fiction, non-fiction or nothing, immediately improved scores on theory-of-mind tests. The finding attracted wide attention.

A replication by three independent research groups, led by Maria Eugenia Panero, randomly assigned 792 participants to the same four conditions and found no advantage for literary fiction on the Eyes test. What did predict scores, in every condition, was how much fiction people had read over their lifetime. The authors suggested that people with strong theory of mind may be drawn to fiction, that long-term reading may slowly strengthen it, or that verbal ability explains part of the link. That is the general pattern in this field: short training effects are fragile, and the steadier associations are correlational. Our guide on whether reading makes you smarter covers the wider evidence on reading.

Trust and scope notes

This page summarises published research for general information. The figures quoted are those reported by the studies listed below. It explains theory of mind in general and does not assess, diagnose or interpret any individual. The IQ Revealed test is an online reasoning test of 40 original items for adults aged 18 and over. It does not measure theory of mind, it cannot diagnose, screen for or rule out autism or any other condition, and it is not a clinical assessment. Our guide to how IQ tests work explains what an online test can and cannot tell you.

IQ Revealed is not affiliated with, endorsed by or connected to the Autism Research Centre, the authors of the Reading the Mind in the Eyes test or the Autism Spectrum Quotient, or the researchers, universities, studies and journals named on this page. Test names are used only to identify the instruments being described.

Frequently asked questions

What is theory of mind?＋

Theory of mind is the ability to understand that other people have their own beliefs, desires, intentions and feelings, which can differ from yours and from the facts, and to use that understanding to explain and predict what they do. Psychologists call it a theory because other people's minds cannot be observed directly; we infer them from what people say and do.

What is an example of theory of mind?＋

A friend leaves her keys on the table, and while she is out of the room someone moves them to a drawer. When she comes back, you expect her to look on the table, because that is where she believes the keys are, even though you know they are in the drawer. Predicting her mistaken search is theory of mind at work. Everyday examples include noticing that someone is joking, keeping a surprise secret and realising that a person who missed a conversation does not know what was said.

At what age does theory of mind develop?＋

In the classic spoken false-belief tests, most three-year-olds give the wrong answer and most five-year-olds give the right one. A meta-analysis of 178 studies found that children move from below-chance to above-chance performance during the preschool years, a pattern that held across countries and task versions. Simpler understandings come earlier: children grasp that people want different things before they grasp that people can believe something false. Studies that measure where infants look suggest some sensitivity to other people's beliefs as early as 15 months.

What is the Sally-Anne test?＋

The Sally-Anne test is a false-belief task. A child watches a story, usually told with dolls: Sally puts a marble in her basket and leaves; while she is away, Anne moves the marble to her box. The child is then asked where Sally will look for her marble when she comes back. The answer that shows understanding of false belief is the basket, where Sally last saw it. The task was used in a 1985 study by Simon Baron-Cohen, Alan Leslie and Uta Frith.

Do autistic people lack theory of mind?＋

That claim was influential from the 1980s, but it is now strongly contested. A 2019 review by Morton Ann Gernsbacher and Melanie Yergeau concluded that the evidence does not support the idea that autistic people are uniquely or universally impaired on theory-of-mind tasks, noted original findings that failed to replicate and called the claim empirically questionable and harmful. The double empathy idea proposes that misunderstanding between autistic and non-autistic people runs in both directions.

Is theory of mind related to IQ?＋

Partly. A 2019 meta-analysis of 18 studies found that, in comparison groups, scores on the Reading the Mind in the Eyes test depended on full-scale and verbal IQ and on age. One reason is that many theory-of-mind tests use words: choosing between labels such as "contemplative" and "suspicious" requires a large emotion vocabulary. So part of what these tests measure overlaps with verbal ability, and a theory-of-mind score should not be read as a separate measure of social skill alone.

Can you improve theory of mind?＋

There is no reliable shortcut. A 2013 study reported that reading a passage of literary fiction immediately improved scores on theory-of-mind tests, but a replication by three independent research groups with 792 participants found no advantage for literary fiction over popular fiction, non-fiction or no reading. People who had read more fiction over their lifetime did score higher, but that link is correlational and may partly reflect verbal ability.

Does the IQ Revealed test measure theory of mind?＋

No. Our test is an online reasoning test of 40 original items for adults aged 18 and over. It does not produce a theory-of-mind score, it cannot diagnose, screen for or rule out autism or any other condition, and it is not a clinical assessment.