Infants develop expectations about what people prefer to eat, providing early evidence of the social nature through which humans understand food, according to a new study conducted at the University of Chicago.

The study, published this month in the Proceedings of the National Academy of Sciences, found infants expect people to share food preferences unless they belong to different social groups. Their understanding changes when it comes to disgust toward a food, with infants expecting such reactions to transcend the boundaries of social groups.

“Even before infants appear to make smart choices about what substances to ingest, they form nuanced expectations that food preferences are fundamentally linked to social groups and social identity,” said Zoe Liberman, a University of California, Santa Barbara assistant professor who completed the research while a UChicago doctoral student.

In past studies researchers found infants could watch what other people ate in order to learn whether a food was edible. The new study looks beyond learning objective properties about foods to examine the expectations infants hold around who will agree or disagree on food preferences.

The study has important implications for policymakers working on public health, particularly obesity. The findings underscore the need to look beyond just teaching children which foods are healthy when combating obesity to focus on the social nature of decisions surrounding what to eat.

“For humans, food choice is a deeply social and cultural affair. These new findings show that infants are tuning into critical information for understanding the social world, as well as for reasoning about food,” said Amanda L. Woodward, the William S. Gray Professor of Psychology at the University of Chicago.

Additional authors of the study were Kathleen R. Sullivan, social science analyst at the U.S. Department of Health and Human Services; and Katherine Kinzler, associate professor at Cornell University.

In conducting the study, researchers used a method based on the duration infants look to determine their expectations: Infants tend to look longer at events they find relatively more surprising.

For example, monolingual infants in the study consistently looked longer when actors who spoke the same language disagreed on their food choice. The same was true when actors who spoke different languages agreed on their food choice. The reactions suggest monolingual infants expected food preferences to be consistent within a single linguistic group, but not necessarily the same across groups.

Responses were different for infants raised in bilingual environments. Bilingual infants in the study expected food preferences to be consistent even across linguistic groups, suggesting diverse social experiences may make children more flexible in determining which people like the same foods.

When it came to disgust for a food, infants looked longer when actors disagreed over a food being disgusting, even when the actors came from different social groups. The finding suggests infants might be vigilant toward potentially dangerous foods, and expect all people to avoid foods that are disgusting, regardless of their social group.