“Parental input has been considered a key environmental factor for infants’ language development, as shown by a wealth of behavioral research. But few studies have looked at how parents’ verbal interactions with babies affect the physical development of their brains. Given the critical growth in children’s language-related activities in their first two years of life, a better understanding of what’s going on in their brains at this time is badly needed.

“Thanks to a long-term intervention study of infant language-learning, researchers at the University of Washington’s Institute for Learning & Brain Science (I-LABS) have a trove of LENA-device home recordings of child vocalizations and parent-child verbal interactions taken at regular intervals throughout babies’ first 24 months.

“For their recent study on the effect of language experience on white-matter development, researchers invited all the families back to the lab for an MRI session when the children were around 2 years old. The MRIs imaged the white matter in the toddlers’ dorsal language system, a brain network that is tied to expressive language development and long-term language ability. They found that the frequency of parents’ verbal interactions with their infants, specifically conversational turns, uniquely predicted myelin density in this system.”