Damage to a small region of the brain behind the forehead can change the moral compass of individuals, making their decision-making more cold and calculated, according to a study published Wednesday in the journal Nature.

Researchers at four American universities tested 30 subjects with a set of extreme moral dilemmas that had a similar theme: whether to harm one person in order to prevent certain future harm to many.

In one scenario, the subjects were told they knew someone had AIDS and that the person planned to infect others, some of whom would die. The subjects were then presented with two options: let it happen or kill the person.

While most subjects wavered or said they would not do it, six individuals with damage to the ventromedial prefrontal cortex (VMPC) — a part of the frontal lobe — stood out in their stated willingness to harm an individual to achieve a utilitarian end.

"Because of their brain damage, they have abnormal social emotions in real life. They lack empathy and compassion," said Ralph Adolphs, Bren professor of psychology and neuroscience at the California Institute of Technology, in a statement.

Among the other 24 subjects, 12 had no brain damage and 12 had brain damage in an area other than the VMPC.

The study suggests an aversion to harming others may be hard-wired into our brain.

Antonio Damasio, the director of the Brain and Creativity Institute at the University of Southern California, described this aversion as a "rejection of the act, but combined with the social emotion of compassion for that particular person."

The findings also raise philosophical questions about the role emotions play in moral decision-making, the authors contend.

"The question is, are the social emotions necessary to make these moral judgments," said Adolphs.

The findings suggest humans are neurologically unfit for strict utilitarian thinking, the authors say, suggesting neuroscience may be able to test different philosophies for their compatibility with human nature.