Then they asked the participants to report their annual income and estimate how much they spent on paying bills, buying gifts for themselves, buying gifts for others and giving to charity.
The first two were considered personal spending and averaged $1,714-a-month, the second two were termed "prosocial" spending and averaged $146-a-month.
"Personal spending was unrelated to happiness," said the researchers. "But higher prosocial spending was associated with significantly greater happiness," they found.
Not content with that, they then studied 16 employees of a company in Boston, asking about their happiness one month before and six to eight weeks after each received a profit-sharing bonus from their employer.
In the second interview they also asked about personal and prosocial spending and once again those who spent more on others were happier.
"The manner in which they spent that bonus was a more important predictor of their happiness than the amount of the bonus itself," the researchers found.
Finally, 46 Canadian students were asked to rate their happiness and then each was given a random envelope containing money, ranging from $5 to $20. Some were instructed to spend it on themselves, others were told to buy a gift for someone else.
At 5 p.m. that day, they were called together again and asked to rate their happiness.
The amount of money had no impact on happiness, but those assigned to buy something for another person reported greater happiness than those told to get something for themselves, the researchers said.
A separate study published in 2006 in the journal Proceedings of the National Academy of Sciences found that the same parts of the brain that produce the good feeling when a person receives a reward also respond when they give to someone else.
Indeed, researchers led by Jordan Grafman at the National Institutes of Health found the reward areas were more active when giving a gift than when receiving one.