You might expect people to be most enthusiastic and opinionated about ideas that they themselves are excited about, but this research suggests that's not the whole story.
"Thinking about what appeals to others may be even more important."
It's one of those conclusions that makes a lot of intuitive sense: you know that feeling you get when you see something on Facebook that you have to share with a specific friend? That moment when you get an image of how they're going to react when they see that news story or this kitten? That, apparently, is your TPJ working overtime.
The TPJ is located around the centre on both sides of the brain, just behind your ears. Its job is to connect us to the thoughts and beliefs of others; the kind of empathy you get from watching a movie or reading a novel. Damage to the TPJ has been known to result in out-of-body experiences: literally stepping outside of yourself.
Three years ago, an MIT team showed that stimulating the TPJ affected moral reasoning: subjects were less likely to care about the inherent morality of a situation (in this case, whether a man should let his girlfriend walk across a rickety bridge) and more about outcomes (did she get across safely?).
So the next time you share a great tweet or a cute picture on Facebook and get exactly the "squee!" you were looking for, remember which brain part to thank.
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