Early neural development of social interaction perception: evidence from voxel-wise encoding in young children and adults.

From a young age, children have advanced social perceptual and reasoning abilities. However, the neural development of these abilities is still poorly understood. To address this gap, we used fMRI data collected 122 3-12-year-old children (64 females) and 33 adults (20 females) watched an engaging and socially rich movie to investigate how the cortical basis of social processing changes throughout development. We labeled the movie with visual and social features, including motion energy, presence of a face, presence of a social interaction, theory of mind (ToM) events, valence and arousal. Using a voxel-wise encoding model trained on these features, we find that models based on visual (motion energy) and social (faces, social interaction, ToM, valence, and arousal) features can both predict brain activity in children as young as three years old across the cortex, with particularly high predictivity in motion selective middle temporal region (MT) and the superior temporal sulcus (STS). Furthermore, models based on individual social features showed that while there may be some development throughout childhood, social interaction information in the STS is present in children as young as three years old and appears adult-like by age seven. The current study, for the first time, links neural activity in children to pre-defined social features in a narrative movie and suggests social interaction perception is supported by early developing neural responses in the STS.Significance Statement This study investigates the neural basis for social scene perception ability in children using fMRI data collected while participants watch a short, animated movie. Unlike most prior studies with movies, we labeled a range of visual and social features in the movie and used machine learning analyses to link each feature to fMRI responses in adults and children ages 3-12. Notably, our results demonstrate strong evidence that children as young as three years old show significant responses to most visual and social features in the movie, including social interaction responses in the superior temporal sulcus (STS), a region in the brain that is well known to be important in social interaction processing in adults.