Infants as young as nine months old prefer individuals who are nice to people like them and mean to others, scientists, including one of Indian-origin, have found.
The study found that babies want individuals who share their tastes to be treated well by others, but want those whose tastes differ from their own to be treated badly. And this innate mean streak grows stronger in the next five months of their life.
Researcher Kiley Hamlin, a professor at the University of British Columbia, conducted the study as a graduate student at Yale University with her adviser Karen Wynn and colleagues Neha Mahajan of Temple University and Zoe Liberman of the University of Chicago.
The study of 200 infants aged between 9 and 14 months introduced babies to two hand puppets that had expressed contrasting preferences (for example, one preferring green beans to graham crackers, the other preferring the crackers to the beans).
Babies who themselves preferred the crackers were much more likely to reach for puppets that liked crackers.
The team wanted to know if infants' preference for similar individuals meant that they hold negative attitudes towards those who are unlike themselves.
Researchers introduced babies to a puppet with the same food preference as the baby and to a puppet with the opposite preference. They then introduced two new puppets: One was helpful and retrieved a dropped rubber ball. The other was mean and took the ball away.
As expected babies of both ages preferred the helper over the meanies when the puppet being assisted liked the same food they did, according to the study published in journal Psychological Science.
But the next finding surprised the researchers: When the puppet that dropped the ball did not share the babies' taste in food, the infants preferred the mean puppet to the helper.
Babies prefer someone who is nice to an individual similar to themselves, but they also prefer someone who is mean to a dissimilar individual.
However, Wynn, said, the results do not necessarily show that babies are born with a mean streak.
"We were surprised - and more than a little chagrined - to find that babies actively prefer individuals who mistreat someone whose tastes differ from theirs," Wynn said.
"But while our findings show that we may be built to dislike differences, we are also built to like similarities - and humans all around the world are similar in a multitude of ways," she said in a statement.
It may be that the more similarities babies - and adults - recognise between themselves and others, the less they will want to see those others harmed, said Wynn.
