There is evidence to show that the Type T personality is something people are born with. It isn’t a lifestyle choice. In fact risk taking has been linked to levels of dopamine, a chemical found in the brain that regulates mood and pleasure. Published research conducted by Dr. Ernest Noble of the University of California links the D2 and D4 dopamine receptor genes to risk-taking behaviour. After his 1998 study, Noble estimated that 20 per cent of people are born with the D2 dopamine receptor while 30 per cent are born with both the D2 and the D4 dopamine receptors. (CBC Online Archives)