This may come as painful news to parents: toddlers are more likely to copy the actions of a crowd than those performed by one person, according to new research in Current Biology.

“When we think of peer pressure, we think of teenagers and the reasons they start smoking or drinking,” says Daniel Haun of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. “We don't necessarily think of two-year-olds as being under peer pressure. But it turns out they are.”

To investigate peer pressure's origins, Haun observed human toddlers and chimpanzees as they learned a simple task: placing a ball into one of three boxes. First the subjects watched other members of their species do it—both as one individual placed a ball three times into one box and as three individuals placed one ball each into a second box.

When it was the observer's turn, both humans and chimps tended to choose the box that was used by the majority. The chimps were even more prone than the children to copy the group. This tendency to conform might have provided an evolutionary benefit that helped humans learn new skills and avoid dangers. “If you know nothing, following the majority isn't a bad strategy,” Haun says.

Haun now wants to see if chimps and toddlers, when performing a familiar task, might switch their behavior to fit with the majority, even if they know that the group is wrong. Such behavior has been observed in older children, although whether it serves any evolutionary advantage is less obvious.