Washington: Babies as young as nine months old can tell whether others are likely to be friends, even before they develop language skills or understand social structures, a new study has found.
Researchers found that nine-month-old infants can engage in reasoning about whether the people they observe are friends based on the person's likes and dislikes.
"This is some of the first evidence that young infants are tracking other people's social relationships," said Amanda L Woodward, from the University of Chicago and co-author of the study.
In the study, 64 nine-month-old infants were randomised into groups and then watched videos showing two adults.
The adults each ate two foods and reacted in either a positive or a negative way to each food they ate. In some videos the adults shared the same reactions, while in others they reacted differently.
"We depicted evaluations of food because food may provide particularly salient social information," said co-author Katherine D Kinzler.
"Eating with family and friends is inherently social, and so infants might be particularly inclined to use eating behaviours to make inferences about social relationships," Kinzler said.
To investigate whether infants linked food reactions to social relationships, the experiment examined how infants responded to subsequent videos, which showed the same adults acting either positively or negatively toward each other.
In the video showing a positive interaction, the adults greeted each other with smiles and said 'Hi!' in a friendly tone of voice.
In the other video, adults turned away from each other, crossed their arms and said 'Hmp' in an unfriendly tone.
The research team assessed the infants' reactions to the videos by measuring the amount of time the babies focused on a still screen at the end of each video.
"When babies see something unexpected, they look longer. It's out of place for them, and they have to make sense of it," Woodward said.
The infants' responses to the videos suggested that they were surprised when adults who liked the same foods behaved negatively toward each other. They also were surprised when adults who disagreed about the foods behaved like friends.
The study's implication is that even at the early age of nine months, babies know that adults who agree with each other tend to act in a friendly way in other contexts.
Infants in the study predicted that people who reacted similarly to the two foods were likely to be friends and were taken off-guard when the videos showed something different.
The findings provide the first evidence that the roots of a critical aspect of social cognition, reasoning about other people's social interactions based on those people's likes and dislikes, can be traced to infancy, according to the authors.
The study was published in the Journal of Experimental Psychology: General.