Italian scientists say they have located the part of the brain that can turn a latin lover into an insanely jealous person or even a stalker.
Researchers at the University of Pisa say the discovery raised the possibility of a test to spot potential aggressors before they begin harassing their victims.
The brain area they have identified is the frontal cortex, which is responsible for learning but also controls emotions such as jealousy.
And when this key part of the brain goes out of kilter, sufferers can turn obsessive, begin stalking, and even kill.
"If jealousy is a completely natural feeling, we're looking at the biochemical imbalance that transforms this feeling into a dangerous obsession," said researcher Donatella Marazziti. "In its extreme forms... it provokes terrifying behaviour such as stalking, or drives people to suicide or murder."
The disorder is also known as Othello Syndrome, after the character in Shakespeare's play who murders his wife after wrongly believing she has been unfaithful.
Pathological obsession and jealousy has special resonance in Italy, after a recent spate of domestic violence and murders.
The scientists pinpointed the brain area by studying patients with schizophrenia, alcoholism and Parkinson's disease, whose symptoms commonly include jealousy.
The precise area is known as the ventromedial prefrontal cortex, which is found just above the forehead, according to the findings, which appear in the journal CNS Spectrums.