Brain reacts to fairness as it does to money and chocolate

In the study, subjects were asked whether they would accept or decline another person's offer to divide money in a particular way. If they declined, neither they nor the person making the offer would receive anything. Some of the offers were fair, such as receiving $5 out of $10 or $12, while others were unfair, such as receiving $5 out of $23.

http://www.newsroom.ucla.edu/portal/ucla/brain-reacts-to-fairness-as-it-49042.aspx