You can’t trick babies. They’ll distrust you.

Researchers in psychology at Concordia University in Montreal have found that infants just over a year old can already get a bead on who is reliable and who is unreliable.

The babies will quickly start ignoring cues from those who are unreliable.

“Even babies detect when someone’s behaviour is not conventional,” says Diane Poulin-Dubois, a professor of psychology at Concordia University. “It seems that they then turn off the ‘learning switch’ that typically makes them learn from that person.”

Poulin-Dubois and colleagues conducted a study with 60 babies between 13 and 16 months of age.

The wee ones were divided into two groups ‘those with a reliable adult and those with an unreliable adult ‘ and shown tasks they could mimic. In the first task, testers looked inside a container and expressed excitement and delight before handing the container to the baby.

In the reliable group, there was a toy inside. In the unreliable group, the container was empty. This was repeated several times.

For the second task, the same adult showed the babies a touch-on light. The tester placed it on a desk and switched it on by leaning forward and using the forehead.

This was repeated three times before passing the light to the infant. Infants who had been tricked in the first experiment were far less likely to imitate the adult. Over two attempts, 34 per cent of infants in the unreliable condition mimicked the adult, versus 61 per cent of infants in the reliable condition.

“Babies are setting down the groundwork for a lifelong skill ‘ remaining vigilant about who is an expert and who is not,” says Poulin-Dubois.

The study was published in the journal Infant Behaviour and Development.