Arcuate Fascicle Maturation Associated With Theory Of Mind Emergence

The developmental stage when child gains the view of others known as Theory Of Mind is associated with the maturation of fibres of a brain structure called the arcuate fascicle, researchers at the Max Planck Institute for Cognitive and Brain Sciences in Leipzig have found.

By the age of four years we begin to understand what other people think and that their beliefs about the world might differ from our own. We then manage to do what 3-year-olds are not yet capable of – we can put ourselves in someone else’s shoes.

If you tell a 3-year-old child the following story of little Jill, they will most probably not understand: Jill puts her chocolate on the kitchen table, then leaves to play outside. While she is gone, her mother puts the chocolate in the cupboard.

Where will Jill look for her chocolate? A 3-year-old child will not understand why Jill would be surprised not to find the chocolate on the table where she left it. It is only by the age of 4 years that a child will correctly predict that Jill will look for her chocolate where she left it and not in the cupboard where it is now.

Something similar can be observed when you show the 3-year-old child a chocolate box that contains pencils instead of chocolates. If you ask the child what another child would expect to be in the box, they will answer “pencils,” although the other child would not know this.

Only a year later, around the age of four years, however, they will understand that the other child had hoped for chocolates. Thus, there is a crucial developmental breakthrough between three and four years.

This is when we start to attribute thoughts and beliefs to others and to understand that their beliefs can be different from ours. Before that age, thoughts don’t seem to exist independently of what we see and know about the world.

That is, this is when we develop a “Theory of Mind.”

Arcuate Fascicle Maturation

The maturation of white matter fibres in the arcuate fascicle, between the ages of three and four years, establishes a connection between two critical brain regions.

One is a region at the back of the temporal lobe that supports adults thinking about others and their thoughts. The other is a region in the frontal lobe that is involved in keeping things at different levels of abstraction, and therefore helps us to understand what the real world is and what the thoughts of others are.

Only when these two brain regions are connected through the arcuate fascicle can children start to understand what other people think. This is what allows us to predict where Jill will look for her chocolate. Interestingly, this new connection in the brain supports this ability independently of other cognitive abilities, such as intelligence, language ability or impulse control.

First author of the study, Charlotte Grosse Wiesmann from the Max Planck Institute in Leipzig, says:

“The strong arcuate fascicle might be the reason why humans are particularly good at understanding what other people think and predicting their actions. Although apes also seem to understand other individuals, they do this to a much lesser extent. This might result from the weaker fibre connection."

The research was supported by funding from the Studienstiftung des deutschen Volkes and the Jacobs Foundation.

Charlotte Grosse Wiesmann, Jan Schreiber, Tania Singer, Nikolaus Steinbeis & Angela D. Friederici
White matter maturation is associated with the emergence of Theory of Mind in early childhood
Nature Communications 8, Article number: 14692 (2017) doi:10.1038/ncomms14692