They might look all cute and bubbly on the outside, but a new study suggests babies have a hidden mean streak – and even wish harm on people who they identify as different from them.

A University of B.C.-led psychology study found that infants as young as nine-months-old embrace those who pick on individuals who don’t share their preferences.

Study lead author Kiley Hamlin said the findings reveal that babies are constantly busy assessing their surroundings, trying to determine who their friends and enemies are.

Hamlin said almost all of the 112 test babies acted the same during testing.

During the study, babies aged nine to 14 months chose a food they preferred to eat, either graham crackers or green beans.

The youngsters were then shown a puppet show where the character demonstrated the same food preference as the baby. Another puppet demonstrated the opposite preference.

The puppets harmed, helped or acted neutrally towards the puppets with different or similar food preferences.

Results showed that the babies far preferred the puppets who harmed the puppet with the opposite food preferences to their own. One baby even planted a kiss on the puppet she liked.

Watch now: UBC baby psychology testing

Hamlin said the findings suggest that babies feel something like schaudenfreude, a German term describing the pleasure experienced when someone you dislike or consider threatening experiences harm.

The babies’ bullying behaviour may be an early version of the social biases experienced by adults. It’s no secret that people tend to gravitate towards those they have things in common with, from sports to career choices to the music they listen to. But study authors believe these preferences can have a dark side, and disliking people who are different may lead us to mistreat them, and excuse – or even applaud – others who mistreat people who are different than us.

“The fact that infants show these social biases before they can even speak suggests that the biases aren’t solely the result of experiencing a divided social world, but are based in part on basic aspects of human social evaluation,” said Hamlin.

The study is published in the journal Psychology Science.