Here's something you probably knew but seems counterintuitive ... Happiness brings success -- not the other way around, at least according to researchers and scientists who study happiness.

"We've learned in 10 years that happy people are more productive at work, learn more in school, get promoted more, are more creative and are liked more," said Martin Seligman, then-president of the American Psychological Association, and founder of the positive psychology movement.

And while success and materialism are great, it doesn't necessarily contribute to happiness.

THURSDAY, June 5 (HealthDay News) -- Levels of a brain chemical known as serotonin govern the way people react to unfair offers when they play the game of life, a new study indicates.

Serotonin, which carries messages between neurons, is involved in emotional control. One recent study found that the expression of anger in women was affected by variations in a gene governing the receptors for serotonin in brain cells.