Before babies learn to speak, they're having actual conversations with their parents, whether the parents realize it or not.
A coo. A babble. A squeal. Inevitably, an adult will make noises back or respond with baby talk. A higher pitch. Exaggerated intonation. In those moments of back-and-forth vocalizations, the responders are training the baby to converse, according to new research co-authored by Martha Pelaez, professor of Education at Florida International University. Rather than something that just naturally develops on its own, the researchers say the foundation for language is actually built in those tiny, often playful, exchanges. Published in the Journal of Applied Behavior Analysis, the research reviews decades of research on how babies learn to vocalize — and argues that conversation actually comes before language.
The study focuses on two key behaviors adults naturally use with babies. The first is immediately repeating sounds a child makes. The second is known as parentese — the exaggerated baby talk voice adults instinctively use with infants. Both are effective in helping the baby develop speech, but the first one — imitating the baby's sounds back to them — has the strongest effects, according to the researchers.
"What may seem like a small interaction actually has huge and important developmental consequences for language development," Pelaez said.
Researchers found that when caregivers immediately responded to babies' sounds — especially by imitating them back — infants vocalized more frequently and produced more speech-like sounds. The effects were seen not only in typically developing infants, but also in children with autism, Down syndrome and developmental delays.
Timing matters.
When an adult immediately mirrored a child's vocalization, babies appeared more engaged, more attentive and more likely to vocalize again. A response delivered seconds later was often far less effective.
"Think of it as a conversation. If someone responds to you several minutes after you speak, the interaction loses connection and its natural flow," Pelaez said. "The same principle applies to infants. Immediate responses help babies recognize that their vocalizations have an effect on the world around them. Those moments are the building blocks of early communication."
The paper also explores why humans may be biologically wired for these exchanges. Caregiver imitation and infant-directed speech may strengthen social bonding, attention and turn-taking — skills critical for communication and survival. Similar forms of infant-directed vocal behavior have even been observed in vocal-learning animals including dolphins, bats and zebra finches.
For clinicians and families, the findings could carry important implications for supporting children with speech delays. The authors note that simple, responsive interactions — especially during infancy — may help strengthen early vocal behavior before formal language emerges.
The research also reinforces something many exhausted parents have suspected all along:
Baby talk isn't nonsense. It may actually be neuroscience in action.
"Talk with your baby, not just to your baby," said Pelaez, who herself is a grandmother that enjoys conversing with her young grandchildren. "Those seemingly small moments are powerful learning opportunities. Language develops through interaction, and every responsive conversation will help build the foundation for future communication."
Pelaez's research interests explore early childhood development, including parent-infant interactions, language development and behavior. As a researcher in the Department of Counseling, Recreation and School Psychology, her work focuses on how early experiences shape learning and social development.
The paper, "Contingency Drives Children's Vocal Behavior," was co-authored by Maithri Sivaraman of Teachers College, Columbia University.
