[language] [Fwd: [evol-psych] Baby babbling linked to brain's language center, not motor skills center]

[H.M. Hubey]

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Thursday, August 29, 2002

Baby babbling linked to brain's
language center,
not motor skills center

Whether baby babbling is fundamentally linguistic (absorbing the
elements of language) or just exercising motor activity (practicing the
mechanics of mouth movement) has never been effectively addressed. Until
now. A team of researchers based at Dartmouth has discovered a strong
link between baby babbling and the language processing centers in the
brain.

Professor Petitto works with 11-month-old Derrin Bilgili to better
understand how babies learn language and the brain's processes that make
this extraordinary feat possible.
(Photo by Joe Mehling '69.)

Laura Ann Petitto, Professor in Dartmouth's Department of Psychological
and Brain Sciences and Department of Education, and graduate student,
Siobhan Holowka at McGill University in Montreal, Quebec, report their
findings in the August 30, 2002, issue of Science.

"This discovery is the first to demonstrate left hemisphere cerebral
specialization for babies' production of language, just like we see in
adults," says Petitto. "This suggests that language functions specialize
in the brain at a very early age."

The researchers found that babies babble with a greater mouth opening on
the right sides of their mouths, indicating left brain hemisphere
activity. They conclude that babbling engages the language processing
centers in the left hemisphere of the brain.

"Right mouth asymmetry" is the phrase used to describe the fact that the
right side of your mouth opens a tad wider than the left while talking.
Human eyesight (or how the brain perceives this act) corrects for this
disparity, so it is virtually unnoticeable. Researchers have studied
right mouth asymmetry in adults to understand the language control
centers in the brain's left hemisphere, a method proven useful to detect
brain damage after heart attacks or strokes. These studies produce a
"Laterality Index," which is a measure of the asymmetry. Holowka and
Petitto are the first to apply this measure to study language in babies.

"We were trying to find a way to further study language development in
babies, but we needed a technique that would not be invasive or
upsetting," explains Petitto. "The Laterality Index was our answer."

The researchers studied videotapes of 10 babies between the ages of five
and 12 months. Taking into consideration any language-specific bias,
five babies were learning English, and five were learning French. On the
videos, two independent coders who were unaware of the study's goals
scored randomly selected segments using the Laterality Index. They
focused on three different kinds of mouth activity: babbles (sounds with
consonant-vowel repetition), non-babbles (vocalizations without
consonant-vowel content or repetition), and smiles (mouth movements with
a known meaning or significance, generally indicating enjoyment, and
often accompanied by contractions around the left eye). By slowing down
the video recordings, the coders could calculate, using the Laterality
Index, the size and nature of the babies' mouth openings for each of the
different kinds of mouth activity.

"We found that all the babies, both English and French, had right mouth
asymmetry when babbling, equal mouth opening for non-babbling, and left
mouth asymmetry for smiles," says Petitto.

Not only do their findings link babbling to the language centers in the
left side of the brain, the results also suggest that a basic expression
of emotion, such as smiling, is linked to the right hemisphere's
emotional centers in the brain, just like adults. Again, this suggests
that sections of the human brain begin to specialize at a very early age.

"We are currently exploring whether this baby-friendly research method
could also be used as a diagnostic tool to determine if there are
linguistic or developmental problems even before a baby can utter its
first word," says Petitto. "The sooner parents and pediatricians
recognize these problems, the sooner they can begin to treat them."

See www.dartmouth.edu/~lpetitto <http://www.dartmouth.edu/%7Elpetitto>
for more information, photos and QuickTime movies.

This study was funded by grants to Petitto, including a grant from
Dartmouth College, The Social Sciences and Humanities Research Council
of Canada, and The Spencer Foundation (United States).

Dartmouth College
Copyright 2002
Trustees of Dartmouth College
All rights reserved

http://www.dartmouth.edu/~news <http://www.dartmouth.edu/%7Enews>
Last updated: 29 August 2002 03:21 PM



http://www.dartmouth.edu/~news/releases/aug02/babble.shtml
<http://www.dartmouth.edu/%7Enews/releases/aug02/babble.shtml>


--
M. Hubey

hubeyh at mail.montclair.edu /\/\/\/\//\/\/\/\/\/\/http://www.csam.montclair.edu/~hubey



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