(CNN) - People are inherently selfish. Research shows we're happier and our lives improve when we focus on ourselves.
Makes sense, right?
So why does research also show that we often put others first and fail to choose what will make us happy?
The problem comes, researcher Jonathan Berman says, when we have to decide between spending the $20 we found on the ground on new shoes and donating it to charity.
If you're walking by a shopping center when you pick up the money, you're more likely to freely spend it on yourself. But if you're walking by a homeless shelter, "suddenly spending $20 on yourself feels so different," Berman says.
Berman and his colleague Deborah Small at the University of Pennsylvania hypothesized that forcing a person to be selfish would be liberating - allowing them to enjoy their self-interest pursuit without feeling selfish.
Berman and Small conducted three separate studies with anywhere from 130 to 250 participants to test their theory. Their results were published this week in the journal Psychological Science.
The first study
In the first study, participants were told they either would receive $3 to spend on themselves or $3 to donate to the United Nations Children's Fund. One group was allowed to choose. Another group was given $3 to spend on themselves; a third group was simply given a receipt for their donation.
The participants were then asked to rate on a scale of 1-7 how much they enjoyed receiving or donating the money and how satisfied they were.
Approximately 40 percent chose to donate to charity. There was no difference in happiness between those who gave to charity and those who didn't.
But participants who were given $3 to spend on themselves were happier than those in the choice group and happier than those forced to donate to charity.
"People do enjoy receiving a lot," Berman says. "They enjoy it particularly because they have no choice."
The second study
In a following study, Berman and Small asked three groups to make a choice. One group had to choose between two gift cards to themselves, the other group had to choose between two gift cards for charity and the third had to choose between giving to themselves and giving to charity.
Again, approximately 40 percent of participants in the choice group gave to charity, and neither choice resulted in more satisfaction. The group that reported being the happiest was the group that had to decide between the two gift cards.
The third study
In the last study, the researchers asked participants their preference, whether they would like to donate to charity or keep the money. They were then told a computer would decide what would happen. In reality, all participants received their preference.
Once again, 40 percent donated to charity. Among those who kept the money, people who believed the computer had made the choice for them felt better about the outcome.