Hi, I'm Craig! Cameras make me embarrassed... and this is Mental Floss on YouTube. Today, I'm going to answer Rennie DiCarlo's big question: Why do we blush when we're embarrassed? Let's get started. 

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So blushing is related to the fight-or-flight response, they both come from the sympathetic nervous system. When you do something embarrassing, your body automatically releases adrenalin. This causes faster breathing, and a faster heart rate, 'cause your body is getting ready to, wait for it, fight or flight. 

Vasodilation also occurs thanks to this release of adrenalin. That's when blood vessels widen and blood flow increases, then the veins in your face respond to that. So they dilate in order to allow this increase in blood to flow through them. And because there's more blood flow in your cheeks than there normally is, they appear red, hence blush. 

Interestingly, a 2004 study published in the journal Psychophysiology found that blushing isn't always symmetrical, and that's the first time I've said a word with three Y's and two H's in it. I'm pretty excited. In the study, they had participants sing to an experimenter which they considered embarrassing - the singing, not the experimenter. The researchers found that when they stared at one side of the person's face while they were singing, blushing was more prominent on that cheek that was being stared at. What! 

So that covers the physiological aspect but it doesn't really explain why we blush. Too bad! No, I'll explain. Scientists aren't sure yet, but they think it's because it may have positive social effects. It may have evolved as a silent way for a person to acknowledge that they've made a mistake.

And this still works today, a 2011 study conducted at the University of Groningen in the Netherlands found that people who were blushing are generally considered more trustworthy. Researchers had students play a computerized prisoner's dilemma, a game in which they decided whether to betray an anonymous prisoner. If they both betrayed each other, they both get 2 years in prison. If one betrayed and one stayed silent, the silent prisoner got 3 years in prison. And if they both stayed silent, they both serve 1 year in prison. So no matter what, someone's going to the slammer. In the game, the virtual opponent betrayed the participant, then the computer displayed a picture of the opponent. If the picture featured a blushing person, the participant was more likely to claim that they would trust that individual in the future. Pictures of non-blushing opponents were considered less trustworthy. And less blushworthy. 

Basically, even though blushing might make an embarrassing situation feel even more embarrassing, it's not all bad. We may have evolved this way considering people are more likely to forgive a blushing person. So just try to blush a lot, or wear a lot of red paint on your face. 

Thanks for watching Mental Floss on YouTube, which is made with the help of all of these embarrassing people, seriously, I can't even. If you have a big question of your own you'd like answered, leave it below in the comments. See you next week.