BLOOMINGTON, Ind. -- How infants respond to their mother's touches and smiles influences their development in a manner much like what young birds experience when learning to sing, according to a research project involving the Department of Psychology at Indiana University Bloomington and the Biological Foundations of Behavior Program at Franklin and Marshall College.
An article on the research, titled "Social interaction shapes babbling: Testing parallels between birdsong and speech," will be published this week in the journal Proceedings of the National Academy of Sciences. The Web site for the journal is http://www.pnas.org/misc/highlights.shtml. The academy's Web site is http://www4.nationalacademies.org/nas/nashome.nsf.
"The main point of our research is how the reaction of the babies to their mother's touches and smiles changes how they talk, and this corresponds to what birds do when learning to sing," said Meredith West, a professor of psychology and biology at IU. She collaborated on the article with Andrew King, a senior scientist at IU, and Michael Goldstein, an assistant professor of psychology at Franklin & Marshall College in Lancaster, Pa.
"This research takes advantage of infants' sociality to understand development as it is constructed by interactions with caregivers," Goldstein said, "and it shows that social learning is a crucial part of vocal development."
Goldstein is the principal author of the article, which he researched as part of his IU doctorate that was supervised by West. King directed the research on birds that was a model for Goldstein's work.
"This is the first time for research showing that babies change how they vocalize in response to social responses -- not sounds, but sights -- by using more mature sounds," West said. "This shows that parent behavior plays a role very early in the process of babies learning to talk, a role that goes beyond simply talking to the infant."
West studies behavior development in animals and humans. She is particularly interested in the development of communication and social behavior in the young.
She said the research shows that babies, and birds, pay attention to the social consequences of sound-making and change their behavior accordingly. So their sounds have a function beyond simply making noise.
"By manipulating how mothers behave," West explained, "we demonstrated that babies can change how they vocalize without copying or imitating their mother's behavior. The mothers did not change how they talked but whether they touched or smiled at the baby. That changed the content of the infant's sounds, as they were more mature or word-like."
Goldstein added, "This project shows that maternal behavior and infant sensory capacities interact to generate the development of more advanced infant behavior. It shows that social learning is a crucial part of vocal development."
The researchers studied 30 infants with an average age of 8 months and monitored their interaction with their mothers over two 30-minute play sessions. This included sessions when the mothers were directed to act in specific ways while responding to the infants, and audio and visual testing equipment monitored the results. An analysis of these results formed the basis of the findings.
"This data provides strong support for a parallel in function between vocal precursors of songbirds and infants. Because imitation is usually considered the mechanism for vocal learning in both situations, the findings introduce social shaping as a general process underlying the development of speech and song," the researchers wrote in the abstract of the journal article.
Funding for the research came from the National Institute of Mental Health, the National Science Foundation and the IU Center for the Integrative Study of Animal Behavior.
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