A study by researchers at New York University and McGill University found that babies who speak one language only expect others to speak one language, but bilingual babies do not assume the same, according to PsyPost.
"Our results not only offer insight into infants' perception of linguistic abilities, but, more importantly, may help us better understand whom they see as good communication partners," study co-author and associate professor in NYU's Department of Psychology Athena Vouloumanos told PsyPost.
Researchers studied the reactions of monolingual and bilingual 20-month-olds while adults spoke in either English or Spanish. Adult A told Adult B where a ball was hidden in front of the child. In one scenario, Adult A explained the location of the ball to Adult B, who always found the ball. In the second scenario, Adult B did not find the ball. The ball's location was never hidden from the 20-month-old.
"Knowing who might make a good communication partner may enhance learning about the many aspects of the world that we learn about from others, including our native languages," said co-author Kristine Onishi, an associate professor at McGill University, according to PsyPost.
A method most often used to measure a baby's expectation is gaze time. The longer an infant looks at something, the more likely it is that what happened was not what they expected, according to PsyPost.
Based on the infants' looking time after Adult B looked for the ball following Adult A's instructions, researchers concluded that monolingual infants did not expect Adult B to understand a second language, even if the infant was raised English-speaking and the instructions were given in English, according to PsyPost. When Adult B responded correctly to Spanish once, monolingual infants raised in English-speaking homes were still surprised when Adult B responded correctly to English another time.
"The monolingual infants assumed that an unfamiliar person would understand only one language while bilingual infants did not, suggesting that infants do not expect all speech to convey information to all people," Vouloumanos said, according to PsyPost.
The results of this study appear in the journal Cognition.
