Neuroscientists have uncovered a common thread between Compulsive gambling, attendance at sporting events, vulnerability to telephone scams and exuberant investing in the stock market based on rewards. And they found that the brain systems that detect and evaluate such rewards generally operate outside of conscious awareness. In navigating the world and deciding what is rewarding, humans are closer to zombies than sentient beings much of the time.

Dr. Jonathan Cohen, a neuroscientist at Princeton, studies a part of the frontal cortex called the anterior cingulate, located in back of the forehead. This part of the brain has several functions, Dr. Cohen said, including the task of detecting errors and conflict in the flow of information being processed automatically.

Brain imaging experiments are beginning to show that when a person gets an unexpected reward, more dopamine reaches the anterior cingulate. When a person expects a reward and does not get it, less dopamine reaches the region. And when a person expects a reward and gets it, the anterior cingulate is silent.
Some people seem to be born with vulnerable dopamine systems that get hijacked by social rewards.