Sure, babies look innocent enough, but a University of British Columbia researcher says they can start ganging up on outsiders as early as nine months old.

Psychology professor Kiley Hamlin conducted a series of experiments with babies, puppets and food while she was a graduate student at Yale and the results are published this month in the journal Psychological Science.

She concluded that humans pick sides, and will reach out to "an enemy of my enemy" even before they can talk.

The experiment starts with kids choosing either graham crackers or green beans from bowls and then watching puppets that pretend to like one food or the other. Sitting on their mothers' laps, they see a series of short skits in which one of the first puppets bounces a ball that slips out of its grasp. In one scenario, a new puppet helps out by giving the ball back. In another, the new puppet steals the ball and disappears — a dastardly deed by baby standards.

Afterward, seventy-five per cent of nine-month-olds and 100 per cent of 14-month-olds reached out to touch the puppet that helped their food friend.

That's expected because researchers know that babies generally prefer nice characters over nasty ones, but the second finding was more surprising, said Hamlin in a telephone interview.

Among those babies who saw the skit with the puppet who preferred a different food — the outsider — all of the 14-month-olds and 81 per cent of the nine-month-olds reached out to the puppet that was mean to it.

" ... the current results would suggest that such biases, rather than being solely the result of accumulated experience ... are based in part on an inborn or early-developing propensity to like those whom we recognize as similar to ourselves and to dislike those who differ from us," she concluded in the study. "These tendencies are already operative in the first year of human life."

"We could question whether infants really like seeing someone they dislike be harmed," Hamlin added on Tuesday. "What they might be doing is saying, 'He's being mean to that guy. He must not like him either. I want to be friends with him,' " Hamlin says.

Hamlin's experiment tested 32 nine-month-old babies and 16 toddlers under the supervision of her adviser at Yale, Karen Wynn, a specialist in evolutionary developmental psychology. Although it's a small sample, the 100-per-cent results among 14-month-olds place the data well beyond the possibility of chance, Hamlin says.

Researchers attempted to remove adult influence by using different people to operate and voice the puppet at various stages without knowing the baby's previous choices. Mothers also closed their eyes while holding their babies.

"Basically, the babies are the only ones with all the information."

It's not all joy with experiments on tiny humans, however. Some potential participants were excused for "fussiness."

Hamlin is continuing similar research at UBC, where she has been an assistant professor for the last three years.

eellis@vancouversun.com