Researchers at Harvard have gotten to the bottom of why so many of us are compelled to share our every thought, movement, like and want through mediums like Twitter, Facebook, Foursquare, Instagram and Pinterest.

In a series of experiments, the researchers found that the act of disclosing information about oneself activates the same sensation of pleasure in the brain that we get from eating food, getting money or having sex. It's all a matter of degrees of course, (talking about yourself isn't quite as pleasurable as sex for most of us), but the science makes it clear that our brain considers self-disclosure to be a rewarding experience.

This may help explain recent surveys of Internet use that show that roughly 80% of posts to social media sites like Twitter and Facebook consist simply of announcements about one's own immediate experience.

Lead researcher Diana Tamir and her co-author Jason P. Mitchell devised a series of experiments to measure the reward response that people get when they talk about themselves.

For part of the study they hooked up test subjects to an MRI machine and watched the participants' brain activity as they answered questions about their own opinions and questions about other people's opinions.

The researchers found that the brain regions associated with reward -- the nucleus accumbens (NAcc) and the ventral tegmental area (VTA) -- were strongly engaged when people were talking about themselves, and less engaged when they were talking about someone else.

They also found that the test subjects would turn down money (just a few cents) to talk about someone else, in order to enjoy the more pleasurable sensation of talking about themselves.

For the second part of the study, the researchers wanted to find out how important having an audience is to listen to one's self-disclosure.

"We didn't know if self-disclosure was rewarding because you get to think about yourself and thinking about yourself is rewarding, or if it is important to have an audience," Tamir said.

As anyone with 700 Facebook friends might have guessed, the researchers found greater reward activity in the brains of people when they got to share their thoughts with a friend or family member, and less of a reward sensation when they were told their thoughts would be kept private.

So perhaps all this explains the confounding behavior of people who over-share on the Internet, even to their detriment. (Think criminals who get arrested after bragging about their crimes on Facebook, the teenage girl whose online venting about her chores led to her dad shooting her laptop, the guy who almost went to jail for complaining about his wife.)

"I think the study helps to explain why people utilize social media websites so often," Tamir said. "I think it helps explain why Twitter exists and why Facebook is so popular, because people enjoy sharing information about each other."

ALSO:

Researchers give dogs MRI: What are they thinking?

Solar-powered catamaran goes around the world in 584 days

Does the first amendment cover clicking 'like' on Facebook?