Four-year-olds can understand what others think

The brain has two systems for thinking about others’ thoughts.


Human social interaction crucially relies on the ability to infer what other people think. Unlike their behavior, other people’s mental states are not visible, and we, therefore, need to infer what is on their mind. This ability has been referred to as Theory of Mind (ToM).

Until now, specialists were inconsistent concerning the age at which children can do such perspective-taking. Scientists at the Max Planck Institute for Human Cognitive and Brain Sciences (MPI CBS), University College London, and the Social Neuroscience Lab Berlin shed new light on this question in a study.

According to the study, this ToM ability is developed around four y when children start explicitly reasoning about others’ beliefs.

This unique ability develops around four years of age because of the maturation of a specific brain network that enables this. Younger children are capable of foreseeing others’ behavior depends on what they think; however, the examination shows that this prediction of behavior depends on a different brain network. The mind appears to have two separate systems to take another person’s point of view, and these mature at various rates.

Different brain structures were involved in verbal reasoning about what the cat thinks as opposed to non-verbal… [more] © MPI CBS
Different brain structures were involved in verbal reasoning about what the cat thinks as opposed to non-verbal… [more] © MPI CBS

Scientists examined these relations in a sample of three-to four-year-old children with the help of video clips that show a cat chasing a mouse. The cat watches the mouse hiding in one of two boxes. While the cat is away, the mouse sneaks over to the other box, unnoticed by the cat. Thus, when the cat returns, it should still believe that the mouse is in the first location.

Scientists then used eye-tracking technology to analyze the looking behavior of the study participants. Both the three- and four-year-olds expected the cat to go to the box where the mouse had originally been. That is, they predicted correctly where the cat was going to search for the mouse based on the cat’s belief.

Interestingly, when the scientists asked the children directly where the cat will search for the mouse, three-year-olds answered incorrectly. Only four-year-olds succeeded. Control conditions ensured that this was not because the younger children misunderstood the question.

Scientists found that different brain structures play a vital role in verbal reasoning about what the cat thinks as opposed to non-verbal predictions of how the cat is going to act. According to scientists, these brain structures are regions for implicit and explicit theory of mind.

These cortical brain regions mature at different ages to fulfill their function. The supramarginal gyrus that supports non-verbal action prediction matures earlier and is also involved in visual and emotional perspective-taking.

First author Charlotte Grosse Wiesmann from the MPI CBS said“This enables younger children to predict how people will act. The temporoparietal junction and precuneus through which we understand what others think—and not just what they feel and see, or how they will act—only develops to fulfill this function at the age of four years.”

Co-author Nikolaus Steinbeis from the University College London said, “In the first three years of life, children don’t seem to fully understand yet what others think. But there already seems to be a mechanism a basic form of perspective-taking, by which very young children simply adopt the other’s view.”

The study is published in the Proceedings of the National Academy of Sciences.


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