MONDAY, Nov. 3, 2014 (HealthDay News) -- Infants are exposed to more speech from mothers during their first year of life, which may be why they often pay more attention to mom, new research suggests.
"Infants respond to both parents in the first months, with a greater response to moms," said study co-author Dr. Betty Vohr, professor of pediatrics at Warren Alpert Medical School of Brown University in Providence, R.I.
As for the listening patterns of the parents themselves, fathers seem to pay more attention to the sounds made by their boys, while mothers appear to listen more to their girls, the study found.
It's not clear why any of this happens. But Vohr said the findings are important because they can guide future research into what she called a crucial period for babies to begin developing language. "Early language exposure is critical for language development. Both parents and, in fact, all adults should be made aware of the importance," she said.
Vohr said previous research has suggested that kids develop better language skills if they're exposed to more adult speech in the home starting at the age of 2 months. However, she added, "there is little information about the language environment for infants beginning in the first days of life through 7 months of age and the relative contribution to language of the mother and father."
That's where the new study comes in. The study included 33 babies and their parents. The researchers outfitted the babies with special vests that recorded audio for up to 16 hours in a row. They recorded audio with the vests when the babies were newborns, around 1 month old (or a bit later for premature infants) and then again at 7 months old, according to the study.
Analysts listened to the recordings with an ear toward sounds made by the babies, the words used by the parents and the way the parents and babies respond to each other. (The study technically looked at male and female voices instead of mothers and fathers specifically, but "we did only analyze two-parent households and the days when both parents were in the home," Vohr said.)
The babies were more responsive to the speech of adult females at 1 month and 7 months. Why might babies be more attuned to mothers? "It may be the pitch of the mother's voice or the proximity," Vohr said, "or the caregiving or many characteristics of the environment." Also, she said, "mothers are typically the primary caregivers with the most direct interaction with their infant."
As for parents interacting with their children, "fathers responded to infants about 27 to 30 percent of the time and mothers 88 percent to 94 percent of the time," Vohr said. Why? Researchers don't know the answer, but "perhaps mothers are more directly involved with the care of the infant through feeding and changing, etc," Vohr said.
That doesn't mean fathers are necessarily destined to play second fiddle. "Infants as a whole respond more to the adults that pay more attention to them and interact with them," Vohr said.
At birth and 1 month, mothers responded more to their girls than their boys. There's also evidence, although less statistically strong, that mothers also responded more to girls at 7 months and that fathers responded more to boys at 1 month and 7 months, according to the study.
As for why mothers listened more to girls and fathers listened more to boys, the study doesn't have an answer on that front either.
Marianella Casasola, an associate professor of human development at Cornell University, praised the study, saying it's unique and valid. She said the next step is to launch more research to understand the reasons why the differences might exist.
For now, Casasola said, "simply learning to talk to your infant is easy to implement with important ramifications for child development." Parents, she said, should "put down their devices, make eye contact and talk to their child."
The study was published online Nov. 3 and in the December print issue of Pediatrics.
For more about speech and language development, visit the U.S. National Institute on Deafness and Other Communication Disorders.