Scientists at the Duke Univesity Medical Center are suggesting they have discovered the region of the brain that determines whether a person will be altruistic or selfish.

Altruism - the tendency to help others without obvious benefit to oneself - appears to be linked to an area called the posterior superior temporal sulcus.

Using brain scans, the US investigators found this region related to a person's real-life unselfish behaviour.

They are now exploring ways to study the development of this brain region in early life and believe such information may help determine how altruistic tendencies are established.

Researcher Dr Scott Huettel explained: "Although understanding the function of this brain region may not necessarily identify what drives people like Mother Theresa, it may give clues to the origins of important social behaviours like altruism."