By James Morgan
Science reporter, BBC News, Chicago
The researchers studied 50 families from diverse backgrounds
Toddlers who use gestures more often have better vocabularies on reaching school age, US researchers say.
They say those who convey more meanings with gestures at 14 months have larger vocabularies at four-and-a-half years and are better prepared for school.
Parents and teachers could help children learn to speak by encouraging the use of gestures, say psychologists from the University of Chicago.
Their study, in Science journal, was announced at the AAAS conference.
The researchers found that children from higher-income families with well-educated parents used more gestures as toddlers.
They also had higher vocabularies at school age.
"Our findings contradict the folklore," said Prof Susan Goldin-Meadow, co-author on the study.
"Your grandma always told you - if you're really articulate you shouldn't have to use your hands at all.
"That's typically what the upper class believes about itself.
"But our findings were surprising - we actually found extra gesturing in these high socio-economic status [SES] families.
"Gesture and speech go hand-in-hand.
"That's interesting and we need to explore what's happening here.
"Vocabulary is a key predictor of school success and is a primary reason why children from low-income families enter school at a greater risk of failure than their peers from advantaged families."
Pointing the way
Psychologists have long stated that families of higher income and education levels talk more with their children and speak to them in complex sentences.
But the study is one of the first to focus on whether gestures, too, have an influence on vocabulary and school preparedness.
The researchers studied 50 families from diverse economic backgrounds.
They recorded video of children with their parent, or primary caregiver, for 90-minute sessions, during ordinary home activities.
Fourteen-month-old children from high-income, well-educated families used gesture to convey an average of 24 different meanings during the 90-minute session.
Meanwhile, children from lower-income families conveyed only 13.
Once in school, students from higher-income families had a comprehension vocabulary of 117 (as measured by a standardised test), compared to 93 for children from lower-income families.
The paper does not establish a causal link between early child gesture and later child vocabulary.
But the authors suggested two possible mechanisms by which one might encourage the other.
"Child gesture could play an indirect role in word learning by eliciting timely speech from parents; for example, in response to her child's point at the doll, mother might say, 'Yes, that's a doll,' thus providing a word for the object that is the focus of the child's attention," they wrote.
The connection also may be more direct, since gestures allow children to use their hands to express meanings when they have difficulty forming words for them.