clipped from money.cnn.com

Why is it so hard for most of us to learn that the old saying "Money doesn't buy happiness" is true?

Our brains come equipped with a biological mechanism that is more aroused when we anticipate a profit than when we get one.

I lived through the rush of greed in an experiment run by Brian Knutson, a neuroscientist at Stanford University.

a display inside the fMRI machine showed me a sequence of shapes that each signaled a different amount of money

If the symbol was a circle, I could win the dollar amount displayed; if it was a square, I could lose the amount shown.

When Knutson measured the activity tracked by the scan, he found that the possibility of winning $5 set off twice as strong a signal in my brain as the chance at gaining $1 did.

On the other hand, learning the outcome of my actions was no big deal. Whenever I captured the reward, Knutson's scanner found that the neurons in my nucleus accumbens fired much less intensely than they had when I was hoping to get it.