Infants track others’ mental states, study

A new brain-imaging study supports the idea that infants as young as 7 months have a basic grasp of other people’s true and false beliefs.

smiling infant
Credit: Kaitlin Southworth

Infants cannot explain their perceptions of external events, and some psychologists think that very young children cannot grasp other people’s mental states until they are 2 to 4 years of age. But, a new study by the University of Illinois suggests that infants can accurately track other people’s beliefs.

Scientists involved 7-month-old infants in the study. They showed them videos of an actor who saw – or failed to see – an object being moved to a new location. Later, they tracked infant’s brain using brain-imaging technique and found that activity in a brain region known to play a role in processing others’ beliefs changed in the infants, just as it did in adults watching the same videos.

The findings, reported in The Journal of Neuroscience, add to the evidence that infants possess at least a basic “theory of mind.

Daniel Hyde, lead author of the study said, “It seems remarkable that an infant could have even a basic understanding of other people’s mental states. But when you consider all the things infants have to learn and how they learn, it makes sense that they would have at least some ability to imagine why people are doing what they are doing.”

Psychology professor Daniel Hyde uses brain imaging to study infant cognition. In a new study, he found evidence to support the idea that infants have a basic knowledge of other people’s mental states.  Photo by L. Brian Stauffer
Psychology professor Daniel Hyde uses brain imaging to study infant cognition. In a new study, he found evidence to support the idea that infants have a basic knowledge of other people’s mental states. Photo by L. Brian Stauffer

In a previous study, Hyde and his colleagues looked at activity in the temporal-parietal junction, a brain region thought to play a role in a theory of mind in adults. They recorded activity in the TPJ as adults viewed a video of an actor watching – or not watching – a puppet move a toy from one location to another.

In this study, scientists used an emerging technology called near-infrared spectroscopy to capture brain activity in the TPJ. This noninvasive technique measures how light scatters on the surface of the brain. Light scatters differently when a brain region is more active – a response to changes in the oxygenation state of blood in that part of the brain.

Hyde said, “Near-infrared spectroscopy offers a way to compare activity changes in adult and infant brains.”

“This method is nice because with the infants, you put a cap on their head, they can sit on their parent’s lap and watch whatever you present to them. They probably feel more comfortable and it’s more natural than other methods.”

“The team found that the TPJ in infants responds very similarly to that of adults when viewing the different video scenarios.”

“The infants, like the adults, had an uptick in activity in the TPJ when watching a scene where the actor failed to observe where the puppet put the toy and, therefore, held a false belief about the location of the toy.”

Hyde said the new findings do not suggest that infants have a fully developed theory of mind in the first year of life.

“This simply provides a foundation for developing a deeper understanding of other people’s thoughts and beliefs.”

The findings reported in The Journal of Neuroscience.