Washington: Infants between 6 and 9 months may only utter “ba-ba” and “da-da,” but they can actually comprehend words for many common objects, according to a new study.
University of Pennsylvania psychologists Elika Bergelson and Daniel Swingley have found that 6-to-9-month-old babies learned the meanings of words for foods and body parts through their daily experience with language.
These findings unseat a previously held consensus about infant learning. It was widely believed that infants between 6 and 9 months, while able to perceive and understand elements of the sounds of their native language, did not yet possess the ability to grasp the meanings conveyed though speech.
Most psychologists believed word comprehension didn’t emerge until closer to a child’s first birthday.
To test this belief, Bergelson and Swingley recruited caregivers to bring their children to a lab to complete two different kinds of test. In the first, a child sat on the caregiver’s lap facing a screen on which there were images of one food item and one body part.
The caregiver wore headphones and heard a statement such as, “Look at the apple,” or, “Where’s the apple?” and then repeated it to the child.
The second kind of test had the same set-up, except that, instead of the screen displaying a food item and a body part, it displayed objects in natural contexts, such as a few foods laid out on a table, or a human figure. For both kinds of test, the question was whether hearing a word for something on the screen would lead children to look at that object more, indicating that they understood the word.
In total, Bergelson and Swingley tested 33 6-to-9-month olds. The researchers also had 50 children from 10 to 20 months complete the same tests to see how their abilities compared with the younger group.
In both the two-picture and scene tests, the researchers found that the 6- to 9-month-old babies fixed their gaze more on the picture that was named than on the other image or images, indicating that they understood that the word was associated with the appropriate object.
This is the first demonstration that children of this age can understand such words.
“There had been a few demonstrations of understanding before, involving words like mommy and daddy. Our study is different in looking at more generic words, words that refer to categories,” Swingley said.
Bergelson and Swingley were also curious to know whether they could observe a pattern of learning during the months from 6 to 9. But, when they compared the performance of 6- and 7-month-old babies with that of 8- and 9-month olds, they found no improvements.
“That is a surprising result. We don’t know why it is that performance remains flat for so long,” Swingley stated.
Factoring in the results of the older babies, the researchers found little improvement until the children reached roughly 14 months, at which point word recognition jumped markedly.
“Maybe what is going on with the 14-month olds is they understand the nature of the task as a kind of game and they``re playing it. Or the dramatic increase in performance at 14 months may be due to aspects of language development we did not measure specifically, including better categorization of the speech signal, or better understanding of syntax,” Swingley added.