By David Derbyshire for MailOnline 13:38 09 May 2010, updated 09:25 10 May 2010
At the age of six months babies can barely sit up - let along take their first tottering steps, crawl or talk.
But, according to psychologists, they have already developed a sense of moral code - and can tell the difference between good and evil.
An astonishing series of experiments is challenging the views of many psychologists and social scientists that human beings are born as 'blank slates' - and that our morality is shaped by our parents and experiences.
Good rabbit, bad rabbit: Simple experiments involving babies have shown that we have a strong morality instinct from an early age
Instead, they suggest that the difference between good and bad may be hardwired into the brain at birth.
In one experiment involving puppets, babies aged six months old showed a strong preference to 'good' helpful characters - and rejected unhelpful, 'naughty' ones.
In another, they even acted as judge and jury. When asked to take away treats from a 'naughty' puppet, some babies went further - and dished out their own punishment with a smack on its head.
Leading research: Professor Paul Bloom, of Yale University, said a series of morality tales featuring puppets were shown to babies of varying ages
Professor Paul Bloom, a psychologist at Yale University in Connecticut, whose department has studied morality in babies for years, said: 'A growing body of evidence suggests that humans do have a rudimentary moral sense from the very start of life.
'With the help of well designed experiments, you can see glimmers of moral thought, moral judgment and moral feeling even in the first year of life.
'Some sense of good and evil seems to be bred in the bones.'
For one study, the Yale researchers got babies aged between six months and a year to watch a puppet show in which a simple, colourful wooden shape with eyes tries to climb a hill.
Sometimes the shape is helped up the hill by a second toy, while other times a third character pushes it down.
After watching the show several times, the babies were
shown the helpful and unhelpful toys. They showed a clear preference for the helpful toys - spending far longer looking at the 'good' shapes than the 'bad' ones.
'In the end, we found that six- and ten-month-old infants overwhelmingly preferred the helpful individual to the hindering individual,' Prof Bloom told the New York Times.
'This wasn't a subtle statistical trend; just about all the babies reached for the good guy.'
Two more tests found the same moral sense.
In one, the researchers devised a 'one-act morality play', in which a toy dog tries to open a box. The dog is joined by a teddy bear who helps him lift the lid, and a teddy who stubbornly sits on the box.
They also made the babies watch a puppet cat play ball with two toy rabbits. When the cat rolled the ball to one rabbit, it rolled the ball straight back. But when the cat rolled it to the second rabbit, it picked up the ball and ran off.
'In both studies, five-month-old babies preferred the good guy - the one who helped to open the box; the one who rolled the ball back - to the bad guy,' said Professor Bloom.
When the same tests were repeated with 21-month-old babies, they were given a chance to dish out treats to the toys - or take treats away.
Most toddlers punished the 'naughty rabbit' by taking away treats. One even gave the miscreant a smack on the head as a punishment.
Although the studies appear to show that morality is hard-wired into babies brains, some psychologists urged caution.
Dr Nadja Reissland, of Durham University, said babies started to learn the difference between good and bad from birth.
'Everything hinges on who decides what is normal,' she said. 'By saying pushing the ball up the hill is helpful, the researchers are making a moral judgement. The babies might just prefer to see things go up rather than down.
'In the other test, perhaps the bear closes the box to prevent the dog from getting in there because there is something dangerous inside. It is like a mother keeping children out of an area where there is something harmful.'