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(CBS News) Ever feel like your "friends" are first to post the mundane things they do in their everyday life on social networking sites? It may be because they are getting as much glee talking about themselves as they might from having sex or eating delicious food.

According to a new study in the Proceedings of the National Academy of Sciences (PNAS), boasting about your activities sparks the "primary rewards" center of your brain.

"These findings suggest that the human tendency to convey information about personal experience may arise from the intrinsic value associated with self-disclosure," the researchers wrote.

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Talking about yourself a lot isn't necessarily a bad thing. The study's authors said that 30 to 40 percent of human conversation is devoted to telling others about what we did. And, our brains tell us it makes us feel good, so we can't help sharing - possibly oversharing - about our activities.



For the study, about 300 people's brains were scanned with functional magnetic resonance imaging (fMRI) while they talked about their own beliefs and the beliefs of their peers. They also offered test subjects cash to stop talking about themselves in another experiment.

It turned out people were willing to give up between 17 to 25 percent of their potential money in order to continue talking about themselves. It made even more sense when coupled with the fMRI results: The more a subject talked about "me," the greater the activity in the mesolimbic dopamine system of the brain -- the part of the brain that senses rewards and pleasure from winning money, doing drugs, or eating a delicious dish. There was also greater reward activity for those who were allowed to share thoughts with friends and peers versus those who were told to think to themselves.

The researchers concluded that this also may account for why four out of five postings on social media networks tend to be about the user's immediate experiences, even though the experiments were conducted with face-to-face interaction. Even though the brain's reward centers light up when reacting to non-rewards, the money incentive experiment proved that it was the ability to talk about oneself that provided pleasure.

"I think the study helps to explain why people utilize social media websites so often," study author Diana Tamir, a psychology graduate student researcher at Harvard University in Boston, told the Los Angeles Times. "I think it helps explain why Twitter exists and why Facebook is so popular, because people enjoy sharing information about each other."

So, continue to like those comments on your friends' Facebook - you might just be making their day better.