When children are in the three to five year old age bracket they are going through rapid language development but their thinking is still concrete and linear. “But from five years old they start to understand what other people are thinking,” said registered clinical psychologist, Dr Angharad Rudkin.

They are more likely to play with a new toy if they are in a same-sex group but they are also more likely to adopt gender-type play. So it will depend on what researchers want to know as to which type of group they use said Rudkin.

By six to 11 years old children are starting to reason. However most six year olds think they are good at everything and have unrealistic expectations she warned. By 10 they begin to know what they can and can’t do – which is often accompanied by a dip in self-esteem.

So how can researchers get the most out of six to 11 year olds? “Mix ages as there is the scaffolding effect; single sex groups do better than mixed sets and give measured praise,” said Rudkin.

By adolescence there is a natural distancing from parents and a growth in peer pressure. Between 12 and 14 is the peak of conformity.

De-bunking myths around lying, Rudkin said children learn to lie between two and three years of age. “It’s not true that we avert our gaze when we lie and liars actually fidget less with their hands,” said Rudkin. “But liars tend to use more negative statements than truth tellers.”

Of particular concern was that adults tend to bias toward rating boys as lie tellers and girls as truth tellers. However, older children were better than adults at detecting lies in children.

“The more experience of children the better people are at picking up lies, but also using follow-up questions helps,” she said.

And children are more likely to tell the truth if they have promised to.