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Toddlers’ Responses to “Baby Talk” Linked to Social, Cognitive, Language Abilities

Research Highlight

Across languages and cultures, caregivers tend to have one thing in common: they speak to babies in a happy, sing-song way that they would never use with adults. This type of speech, sometimes called “infant-directed speech,” “baby talk,” or “motherese,” is a particularly exaggerated form of emotionally expressive speech. In a recent study, researchers found that toddlers respond to this emotionally expressive speech in different ways, and these varied responses are linked with their social, linguistic, and cognitive abilities.

Supported by the National Institute of Mental Health (NIMH), the study highlights an early developmental mechanism that may contribute to differences in social interaction and communication that are characteristic of autism spectrum disorder (ASD)

The research team, led by Karen Pierce, Ph.D. , and Eric Courchesne, Ph.D. , of the University of California, San Diego, studied 71 toddlers who were part of an ongoing study. Of these toddlers, 40 had an ASD diagnosis, and 31 did not. The researchers already had data from standardized measures that assessed the toddlers’ ability levels across various domains, including social interaction, language and communication, motor function, perception, and daily living. 

For this study, the researchers used functional MRI (fMRI) to measure the toddlers’ brain activity in response to three levels of emotionally expressive speech: mildly positive speech, moderately positive speech, and highly positive infant-directed speech. They did this while the toddlers were asleep to assess their intrinsic brain responses to different types of speech without any influence of interest, motivation, or attention.

The toddlers also participated in a novel eye-tracking task that measured the time they spent looking at two video clips. One video featured a person telling a story using infant-directed speech, while the other featured technological sounds and images. The videos were displayed side-by-side on a screen—the display was set up such that looking at one of the clips would activate that clip, causing it to play. Thus, the relative amounts of time the toddlers spent looking at the two videos indicated which clip they actively preferred to look at.

To understand how the toddlers’ brain and behavioral responses mapped onto developmental outcomes, the research team used a novel statistical approach to aggregate the data and identify groups of children who were most similar to one another. This analysis revealed four distinct groups.

The children in group 1, most of whom did not have an ASD diagnosis, showed relatively high levels of brain activity in response to all three levels of emotionally expressive speech and spent considerably more time looking at the infant-directed speech clip than the other clip. They also had the highest levels of social, language, and cognitive abilities.

In contrast, the children in group 4, most of whom had an ASD diagnosis, showed relatively low brain activity in response to the infant-directed speech. They also spent much less time looking at the clip with infant-directed speech. In addition, they had relatively lower levels of social, language, and cognitive abilities.

The children in groups 2 and 3 had brain responses, looking preferences, and social and language abilities that fell between those of groups 1 and 4.

Together, these findings suggest that toddlers vary in their responses to emotionally expressive speech—while some seem drawn to this speech, others do not. Importantly, the way toddlers respond to emotionally expressive speech appears to be linked with social, linguistic, and cognitive development.

According to the researchers, this finding lends weight to the theory that a brain-based orientation toward emotionally expressive speech may prime infants to pay attention and respond to infant-directed speech. This, in turn, may promote an interactive caregiver-infant loop that supports infants’ socioemotional development and learning. They hypothesize that a reduced response to emotionally expressive speech could disconnect this caregiver-infant loop and may account for some of the developmental differences often seen in children with ASD.

The findings also underscore the fact that children show broad variation in brain activity, behavior, and ability that is not always reflected by diagnostic categories such as ASD. Using aggregated data to identify distinct groups allowed the researchers to determine how the toddlers’ responses to emotionally expressive speech mapped to various developmental measures, regardless of diagnostic status.

Further research to clarify how children’s responses to emotionally expressive speech shape their earliest social interactions and overall developmental trajectories could help researchers and clinicians identify points for intervention.


Xiao, Y., Wen, T. H., Kupis, L., Eyler, L. T., Goel, D., Vaux, K., Lombardo, M. V., Lewis, N. E., Pierce, K., & Courchesnse, E. (2022). Neural responses to affective speech, including motherese, map onto clinical and social eye tracking profiles in toddlers with ASD. Nature Human Behaviour, 6, 443-454.  


MH118879 , MH104446