It's no secret that children learn to speak when they are spoken to — the more the better.

But new research led by University of Pennsylvania scientists suggests that the quality of the parents' speech, not the quantity, is what really makes a difference in building a child's vocabulary.

What's more, although past research found that children of wealthier and more educated parents were more likely to hear lots of words, the new study found no connection between parents' quality of speech and their socioeconomic status.

Anyone, in other words, should be able to give a kid a leg up.

"Kids really learn the meanings of words in one or two exposures," said Penn's Lila R. Gleitman, one of the study's authors and a professor emerita of psychology and linguistics. "It's a matter of talking to your child, instead of talking at your child."

Start 'em young

The study, a collaboration with University of Chicago researchers, was published in Proceedings of the National Academy of Sciences. The authors did not attempt to identify the specific elements that make up quality speech.

Instead, they played multiple videos of 50 parents speaking to their toddler children and measured how easy it was for untrained observers to guess what the parents were saying with the sound turned off. The observers were 218 undergraduates from Penn and La Salle University.

After 30 seconds had elapsed in each video, a beep sounded, and the students had to guess what word the parent was saying at that moment — common words such as ball, dog, book and water.

The observers guessed the mystery words accurately 5 to 38 percent of the time.

The parents whose words were easier to guess also seemed to have an impact on the toddlers they were addressing. On average, the higher the quality of speech as measured by the observers, the better the child's vocabulary three years later.

Faster learners

That previous studies have shown an impact from the sheer number of words spoken may be largely because the greater the quantity of words, the higher the chance that the child will hear some that are spoken with high quality, said Penn psychology Prof. John C. Trueswell, another one of the authors.

More research is underway on just what the characteristics of quality speech are. But Trueswell said they were the kinds of things one might expect, such as talking about objects that are present, gesturing to the object in question and looking to see if the child is paying attention to the object. □