There is nothing cuter than a newborn sticking out its tongue in response to you doing the same. Now research suggests that such mimicry might be just a coincidence, at least in the youngest babies. The study challenges the prevailing notion in developmental psychology that imitation is ingrained at birth.

Psychologists Janine Oostenbroek, Virginia Slaughter and their colleagues at the University of Queensland in Australia tested 64 infants at one, three, six and nine weeks old for their ability to imitate nine gestures and facial expressions that previous studies have suggested infants can mimic. They hoped to link individual babies' mimicry to their cognitive development, but instead they could not find that babies imitated at all.

“Babies do increase their activity when they're in face-to-face contact with an adult, but they don't specifically match what the adult is doing,” Slaughter says.

The study, published in May in Current Biology, rekindles a 40-year-old controversy, which raged after newborn imitation was first documented in 1977. After that initial paper, findings went back and forth for decades. Then in the 1990s, publications skewed to only positive results, perhaps indicating a systemic bias. The authors say they have heard from colleagues who could not get papers published when they did not find imitation. “I hope our study does help some of the negative results to be aired,” Oostenbroek says.

Critics of the new study point out that the researchers did find an effect when comparing tongue protrusion with mouth opening, a classic test used in many studies with positive results. The babies were indeed more likely to stick out their tongue when researchers did than when the researchers opened their mouth—but crucially, they were also just as likely to stick out their tongue in response to the other seven gestures. If the babies had truly been imitating, they should do so across all conditions, the investigators explain.

Newborn imitation is often used as evidence for the idea that human mirror neurons are engaged at birth. These results suggest the reality may be more complicated. The finding does not mean, however, that aping adults is not a fundamental part of early communication and learning, says evolutionary psychologist David Bjorklund of Florida Atlantic University, who was not involved with the study. Mimicry probably just takes a few months to develop.