How putting a voice and face together in early infancy could determine vocabulary, language development

MIAMI, June 20, 2023 /PRNewswire/ -- Matching the sight and sound of speech — a face to a voice — in early infancy is an important foundation for later language development.

This ability, known as intersensory processing, is an essential pathway to learning new words. According to a recent study published in the journal Infancy, the degree of success at intersensory processing at only 6 months old can predict vocabulary and language outcomes at 18 months, 2 and 3 years old.

"Adults are highly skilled at this, but infants must learn to relate what they see with what they hear. It's a tremendous job and they do it very early in their development," said lead author Elizabeth V.  Edgar, who conducted the study as an FIU psychology doctoral student and is now a postdoctoral fellow at Yale University. "Our findings show that intersensory processing has its own independent contribution to language, over and above other established predictors, including parent language input and socioeconomic status."

Edgar and a team at FIU psychology professor Lorraine E. Bahrick's Infant Development Lab tested intersensory processing speed and accuracy in 103 infants across three years, between the ages of 3 months to 3 years old, using the Intersensory Processing Efficiency Protocol (IPEP). This tool was created by Bahrick and co-investigator FIU Research Assistant Professor of Psychology James Torrence Todd and colleagues.

Designed to present distraction or simulate the "noisiness" of picking out a speaker from a crowd, the IPEP presents several short video trials. Each trial depicts six faces of women displayed in separate boxes on the screen at once. All the women appear to be speaking. However, the soundtrack that matches only one of the women speaking is heard on each trial. With an eye tracker that follows pupil movement, the researchers could measure if the babies made the match, as well as how long they watched the matching face and voice. 

Then, the data was compared with language outcomes at different stages of development — such as how many unique and total words children used. Results revealed infants who looked longer at the correct speaker were later found to have better language outcomes at 18 months, 2 and 3 years old.

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SOURCE Florida International University