Teaching a child to talk is among the most important things a parent can do, but many parents are uncertain about how (baby talk or adult talk?) and when to begin. Premature babies, who are already at a higher risk of developmental problems, may benefit from being spoken to directly, like an adult, and as soon as possible.

Researchers, led by Dr. Betty Vohr, a professor of pediatrics at Brown University conducted a study looking at how talking to premature babies while they were in the neonatal intensive care unit (NICU) affected language development later on. Conversation in the NICU, whether it’s between doctors, nurses, or other parents, is rarely directed toward the babies, and parents sometimes go back to work so that they can save parental leave for when the baby comes home, Vohr said. But leaving these babies alone could be delaying their development, as babies who were spoken to while in the NICU developed language faster. “The brain is a marvelous computer. It’s enhanced the more it’s stimulated,” Vohr told HealthDay.

The study involved 36 infants born at an average of 27 weeks, which is considered to be very preterm — a full term lasts about 40 weeks. A few weeks later, at what would have been week 32 of pregnancy, the researchers recorded 16 hours of interaction between the babies and their parents, looking for adult words, child vocalizations, and instances when either the child or parent responded to each other’s sounds within five seconds. These recordings logged about 1,289 words, 15 parent-child responses, and 77 child vocalizations. At what would have been 36 weeks, another recording found that adult words jumped to 8,255, child vocalizations rose to 153, and parent-child responses more than doubled, coming in at 36.

Next, the researchers waited until the babies were 7 and 18 months old (corrected age) to perform cognitive and language tests measuring their ability to communicate and express themselves, whether it was through vocalizations or actual words. They found that every 100 adult words a baby heard translated into an added two points on the language scale at 18 months. “To me, it’s amazing that eight weeks before their expected delivery, the role of the parent is so powerful in predicting language outcome,” Vohr said, according to Time.

That role involves speaking directly to the child, according to Vohr, who said that although babies can’t communicate with language, they are still able to respond through vocalizations. That’s in contrast to learning language from hearing other nurses speaking to each other or from mothers who only held them, without saying much. “Children learn from conversations going on around them, but the back and forth communication is the most important,” Vohr told HealthDay.

The findings add the debate on how parents should speak to newborn babies. Although many parents will say that adult talk is the best route, a study from last month found that baby talk could improve language development as well. Meanwhile, another study from last year found that babies who heard fake words while still in the womb were able to recognize them once they were born, suggesting that babies are capable of learning words beyond baby talk.

Although the study was small, the researchers believe that the results could have widespread implications. One in eight babies are born prematurely in the United States, according to the Centers for Disease Control and Prevention. This puts them at risk for a number of health problems, including respiratory diseases, cerebral palsy, and hearing loss. Talking to premature babies as soon as they’re born is just one method of reducing some of these risks. “Kids born prematurely are at risk of having speech and language delays or deficits. This has the potential to help, and it promotes the idea of the benefit of mom or another family member being there and talking to the baby,” Lauren Kobritz Krause, chief of speech-language pathology at La Rabida Children’s Hospital in Chicago, told HealthDay. “Talking and interaction helps with vocabulary development. Talk to your child and be part of their world, and include them in your world throughout the day.”

Source: Caskey M, Stephens B, Tucker R, et al. Adult Talk in the NICU With Preterm Infants and Developmental Outcomes. Pediatrics. 2014.