While previous research has shown that babies generally prefer kind actors, the new study - published by the Association for Psychological Science - is the first to suggest that infants condone antisocial behavior when it is directed at individuals who are dissimilar.
"Our research shows that by nine months, babies are busy assessing their surroundings, trying to determine who is friend or foe," says Prof. Kiley Hamlin of UBC's Dept. of Psychology, lead author of the study. "One important way they make these distinctions, our study finds, is based on perceived differences and similarities."
To explore this, researchers had babies choose which food they preferred: graham crackers or green beans. The infants then watched a puppet show in which one puppet demonstrated the same food preference as the infant, while another exhibited the opposite preference.
In the experiments, other puppets harmed, helped or acted neutrally towards the puppets with different or similar food preferences. Prompted to pick their favorite puppet, infants demonstrated a strong preference for the puppets who harmed the "dissimilar" puppet and helped the "similar" one - one infant even planted a kiss on the puppet she liked.
"These findings suggest that babies either feel something like schaudenfreude - pleasure when an individual they dislike or consider threatening experiences harm," says Hamlin. "Or babies have some early understanding of social alliances, recognizing that the 'enemy of their enemy' is their friend."
Hamlin describes the behaviour as an early form of the powerful, persistent social biases that exist in most adults, who favour individuals who share their origins, languages, appearances - even birthdays and sports affiliations - over people with whom they have fewer things in common.
The findings suggest that when infants aged 9-14 months make social evaluations, they assess not only what people do (e.g., act nice or mean) but also to whom they do it (e.g., a person who is liked or disliked), says Hamlin, who performed the research as a graduate student of Prof. Karen Wynn of Yale University.
While studies show that humans tend to gravitate toward people who have things in common, these preferences can have a dark side, Hamlin says: 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.
This does not mean that more extreme outcomes, like xenophobia and intergroup conflict, are inevitable, Hamlin says. "Rather, this research points to the importance of socialization practices that recognize just how basic these social biases might be and confront them head-on," she concludes.