If you want your kids to speak the truth, it is best not to threaten to punish them if they lie.

In an experiment involving 372 children aged between four and eight, researchers found that children were less likely to tell the truth if they were afraid of being punished than if they were asked to tell the truth either because it would please the adult or because it was the right thing to do and would also make the child feel good.

“The bottom line is that punishment does not promote truth-telling,” said lead researcher Victoria Talwar from McGill University’s department of educational and counselling psychology.

“In fact, the threat of punishment can have the reverse effect by reducing the likelihood that children will tell the truth when encouraged to do so,” Talwar added.

During the study, the team left each child alone in a room for one minute with a toy behind them on a table, having told the child not to peek during their absence.

While they were out of the room, a hidden video camera filmed what went on.

When the researchers returned, they asked the children whether they had turned to look back at the toy.

Nearly 68 percent of the children took a peek. For every 1-month increase in age, children became slightly less likely to do so.

When the children were asked whether or not they had looked back, nearly 67 percent of them lied.

The researchers found that while younger children were more focused on telling the truth to please the adults, the older children had better internalized standards of behaviour which made them tell the truth because it was the right thing to do.

“This is useful information for all parents of young children and for the professionals like teachers who work with them and want to encourage young children to be honest,” Talwar said.

The study appeared in the Journal of Experimental Child Psychology.