The moral copass, technically named the right temporo-parietal junction, lies just behind the right ear in the brain
Scientists have discovered a real-life 'moral compass' in the brain that controls how we judge other people's behaviour.
The region, which lies just behind the right ear, becomes more active when we think about other people's misdemeanours or good works.
In an extraordinary experiment, researchers were able to use powerful magnets to disrupt this area of the brain and make people temporarily less moral.
The study highlights how our sense of right and wrong isn't just based on upbringing, religion or philosophy - but by the biology of our brains.
Dr Liane Young, who led the study, said: 'You think of morality as being a really high-level behaviour. To be able to apply a magnetic field to a specific brain region and change people's moral judgements is really astonishing.'
The moral compass lies in a part of the brain called the right temporo-parietal junction. It lies near the surface of the brain, just behind the right ear.
The researchers at the Massachusetts Institute of Technology used a non-invasive technique called transcranial magnetic stimulation to disrupt the area of the brain.
The technique generates a magnetic field on a small part of the skull which creates weak electric currents in the brain. These currents interfere with nearby brain cells and prevent them from firing normally.
In the first experiment, 12 volunteers were exposed to the magnetic field for 25 minutes before they were given a series of 'moral maze' style scenarios.
For each of the 192 scenarios, they were asked to make a judgement about the character's actions on a scale of 1 for 'absolutely forbidden' to 7 for 'absolutely permissible'.
In the second experiment, the magnetic field was applied to their heads at the time they were asked to weigh up the behaviour of the characters in the scenario.
In both experiments, the magnetic field made the volunteers less moral.
One scenario described a man who let his girlfriend walk over a bridge he knew was unsafe. The girl survived unharmed.
Under normal conditions, most people rate the man's behaviour as unacceptable. But after getting the magnetic pulse, the volunteers tended to see nothing wrong with his actions - and judged his behaviour purely on whether his girlfriend survived.
Another scenario described two girls visiting a chemical plant where one girl asks her friend to put sugar in her coffee.
The friend uses powder from a jar marked 'toxic' - but as the powder turns out to be sugar, the girls if unharmed.
Volunteers with a disrupted moral compass tended to rate the girl's behaviour as permissible because her friend was not injured - even though she was aware the powder came from a jar labelled toxic.
Throughout the experiment, irresponsible or deliberate actions that might have resulted in harm were seen as morally acceptable if the story had a 'happy ending', they reported in the journal Proceedings of the National Academy of Sciences.
It's not the first time that scientists have found parts of the brain that specialise in ethics and morality. Last year American scientists claimed to have found a "god spot" - a region of the brain that controls religious belief.
By David Derbyshire