Whether lying about raiding the biscuit tin or denying they broke a toy, all children try to mislead their parents at some time. Yet it now appears that babies learn to deceive from a far younger age than anyone previously suspected.

Behavioural experts have found that infants begin to lie from as young as six months. Simple fibs help to train them for more complex deceptions in later life.

Until now, psychologists had thought the developing brains were not capable of the difficult art of lying until four years old.

Following studies of more than 50 children and interviews with parents, Dr Vasudevi Reddy, of the University of Portsmouth's psychology department, says she has identified seven categories of deception used between six months and three-years-old.

Infants quickly learnt that using tactics such as fake crying and pretend laughing could win them attention. By eight months, more difficult deceptions became apparent, such as concealing forbidden activities or trying to distract parents' attention.

By the age of two, toddlers could use far more devious techniques, such as bluffing when threatened with a punishment.

Dr Reddy said: "Fake crying is one of the earliest forms of deception to emerge, and infants use it to get attention even though nothing is wrong. You can tell, as they will then pause while they wait to hear if their mother is responding, before crying again.

"It demonstrates they're clearly able to distinguish that what they are doing will have an effect. This is essentially all adults do when they tell lies, except in adults it becomes more morally loaded."

She added: "Later it becomes more sophisticated by saying, 'I don't care' when threatened with a punishment - when they clearly do."

Dr Reddy thinks children use early fibs to discover what kinds of lie work in certain situations, and also learn the negative consequences of lying too much.