The gene that makes us once bitten, twice shy

From Nature:

News2007 Most people tend to learn from their mistakes and avoid making the same blunder twice. Now research reveals a genetic mutation that helps to determine the extent to which certain people are doomed to repeat history.

Drug addicts, alcoholics and compulsive gamblers are known to be more likely than other people to have this genetic mutation, which leaves them with fewer receptors of a certain type in the brain. These receptors — called D2 receptors — are activated when levels of the neurotransmitter dopamine drop. Dopamine is responsible for signalling fun and pleasure in the brain. But dopamine also helps us learn. When we make a pleasurable decision, dopamine is a chemical treat, urging the brain to repeat the choice. Being deprived of such a treat should theoretically activate D2 receptors and encourage people not to make that same decision again.

So it had been theorized that people with fewer D2 receptors might be less capable of learning from negative reinforcement.

More here.