Professor Sandra Waxman, of the Department of Psychology, found that sign language, like spoken language, supports infant cognitive development.
In a groundbreaking new study to be published in October, Waxman and a team of researchers discovered that sign language offers 3- and 4-month-old infants a cognitive advantage in forming object categories.
The study was conducted using 113 hearing infants who had never been exposed to ASL or any other sign language. The infants were divided into two categories: an ASL condition and a non-linguistic control condition. Each group viewed eight distinct images from a single category, for example, eight fish, but the infants in the ASL condition were introduced to the images by a woman signing about the objects. The infants in the control condition did not see or hear any kind of language.
Next, in the test phase, all infants viewed two static images: a new member of the same category (e.g., a new fish) or a new object from an entirely different category (e.g., a dinosaur). The researchers found that at three and four months, infants in the ASL condition, but not the control condition, successfully formed the object category (e.g., fish).
“What surprised us the most was that it was specifically the linguistic elements of the ASL that did the trick — not merely pointing and gesturing. Pointing and gesturing are communicative signals for sure, but they are not linguistic signals,” said Waxman.
This result mirrored the effects observed at this age when infants listen to their native spoken language. The study demonstrates that human infants, whether hearing or deaf, are equipped to link language — whether spoken or signed — to core cognitive processes like object categorization.
This study builds on other research from Waxman’s lab that showed how infants link acoustic signals to cognition.
“We had already established a precocious link between acoustic signals to infant cognition. But we had not yet established whether this initial link is sufficiently broad to include sign language, even in infants never exposed to a sign language,” Waxman said. “This study is important because it shows the power of language, writ large.”
Read more about this study in Northwestern Now.