Seeing eye to eye acts as an invitation for mimicry, triggering mechanisms in the frontal region of the brain that control imitation, say scientists.
The results could be the first clues to understanding why some people, such as children with autism, struggle to grasp when they are expected to copy the actions of others in social situations, the researchers said.
Dr Antonia Hamilton, who led the research, said: "Eye contact seems to act as a message that says 'Copy me now'."
The team of psychologists, which also included doctoral student Yin Wang and Dr Richard Ramsey, used functional magnetic resonance imaging (fMRI) to scan the brains of volunteers while they watched videos of an actress who sometimes would make eye contact with them while opening or closing her hand.
The participant was told they should open their own hand whenever they saw the actress move her hand so in some trials the participant was copying the actress and in other trials they were not.
Because previous behavioural measurement such as response time revealed that the participant unconsciously copied the actress faster when the actress provided eye contact, the scientists analysed the brain imaging data to find which brain areas controlled the decision to copy.
The analysis used a new mathematical method called dynamic causal modelling to compute the information processing in the brain, which has never been applied to imitation before.
The data showed that mirror neuron brain regions do play a role in the copying task.
More importantly though, it revealed that these regions are controlled by the medial prefrontal cortex, an area of the brain associated with planning complex cognitive behaviours, expressing personality, decision-making and responding to social situations.
The study has been published in the Journal of Neuroscience.