Eating chocolate make us feel better

In one experienment, college students volunteered to report on their mood and emotional states (hunger, boredom, fear, joy, and guilt) before and after eating chocolate or apples twice a day for six days. As can be seen from the resulting chart above, eating chocolate resulted in an immediate elevation in mood, much stronger than that associated with eating an apple. What's more, this difference spanned the entire duration of the task. The researchers found similar results for "joy," as well as a decrease in "tiredness" compared to eating nothing.

Source: Macht, M., & Dettmer, D. Everyday mood and emotions after eating a chocolate bar or an apple. Appetite, 46, 332-336, 2006.