What Are Babies Thinking Before They Start Talking?

Babies as young as five months old make distinctions about categories of events that their parents do not, revealing new information about how language develops in humans. The research by Sue Hespos, assistant professor of psychology at Vanderbilt University, and Elizabeth Spelke, professor of psychology at Harvard University, was published in the July 22 issue of Nature in the article “Conceptual precursors to language.”

“It’s been shown in previous studies that adults actually categorize things differently based on what language they speak,” Hespos said. “So, if language is influencing adults’ thought, one of our questions was, what’s going on with preverbal infants? Do children think before they speak?

“Language capitalizes on a pre-existing system of ‘I live in a 3-D world, I know how objects behave and interact,’” she continued. “This pre-existing ability suggests that children do think before they speak.”

Previous research has found that infants are sensitive to the acoustic variations that signal meanings in all the world’s languages that adults can no longer hear, even those variations that their own language does not use and that the adults around them no longer hear. For instance, an adult native-English speaker will not hear all of the sounds of Korean and vice versa. Infants hear these subtleties but lose this awareness as their language skills develop over the first year of life.

“The languages of the world vary both in the sounds they require speakers to distinguish and in the meanings they require speakers to convey, and these differences influence what speakers of a language readily hear and think about,” Spelke said. “Our research asked how these differences arise: Does the experience of learning to speak English or Korean make you aware of the categories your language honors?”

The example they used to explore this question was differences between how different languages describe space. For example, the distinction between a tight fit versus a loose fit is marked in Korean but not in English. A cap on a pen would be a tight fit relationship, while a pen on a table would be a loose fit relationship. English does not mark this distinction in the same way, instead emphasizing the “containment” versus “support” relationship, for example: the coffee is in the mug or the mug is on the table.

Hespos and Spelke tested whether five-month-old infants from native English-speaking homes noticed whether objects fit tightly or loosely. The tests were based on infants’ tendency to look at events that they find to be novel. Infants were shown an object being placed inside a container that fit either tightly or loosely until the time they looked at the object being placed inside the container decreased. They were then shown new tight and loose fit relationships. The researchers found that the babies looked at the objects longer when there was a change between tight or loose fit, illustrating that they were detecting the Korean concept.

Hespos and Spelke also conducted the experiment with adults to confirm that English-speaking adults do not spontaneously make the tight versus loose fit distinction.

“Adults ignore tight fit versus loose fit and pay attention to ‘in’ versus ‘on,’” Hespos said. “Adults were glossing over the distinction that the babies were actually detecting.”

“These findings suggest that humans possess a rich set of concepts before we learn language,” Spelke added. “Learning a particular language may lead us to favor some of these concepts over others, but the concepts already existed before we put them into words.”

Hespos is a member of the Vanderbilt Kennedy Center for Research on Human Development and the Vanderbilt Vision Research Center. Spelke is co-director of Harvard’s Mind/Brain/Behavior Initiative. The research was supported by grants from the National Institutes of Health.