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The blush response

15 December 2013

I have a problem with blushing. Not the physical act of having my face turn red when I make a fool out of myself, mind, but the actual concept of the blush response. Why do we blush? What’s the evolutionary value of showing people around that we’re embarrassed? What could possibly be the point?

The physiology

No blushing here. But then again, she's not human, is she?

No blushing here. But then again, she’s not human, is she?

I find that the best way to get answers is to learn more about the problem. So what is blushing exactly?

From a physiological point of view blushing can be described as an autonomous phenomenon where our facial capillaries dilate to increase the blood flow in the surface of the skin, turning it red. It happens involuntarily when embarrassed or under emotional stress. The increased blood flow also make the face (and other parts also blushing, like neck or ears) feel hot and uncomfortable. The response usually soon fades away and normal skin colour returns within a few minutes.

Caught with our pants down

"Ok, you saw through that one, did you? Don't I just feel like a proper tit right now?"

“Ok, you saw through that one, did you? Don’t I just feel like a proper tit right now?”

Ok, so blushing is a physiological representation of the emotional state of embarrassment. Fair enough. We get caught telling a lie, we feel exposed and embarrassed and we blush. And since we have little or no control over this phenomenon, it stands to reason it would have some kind of evolutionary value. After all, it costs extra energy exposing our warm blood to the outer layers of our skin and that cost must be counter-weighted by some benefit, or it would have been selected against and disappeared millions of years ago.

As we blush when we’re exposed with not telling the truth, perhaps blushing is a lie detector alarm? Perhaps we’re supposed to get caught when lying – especially since we as humans are so good at it. Could it be that the blush response is a control device to make sure we don’t lie our heads off? After all, if we were to lie too much, we would potentially sabotage our position within the group and get left on our own. And we wouldn’t have survived on our own…

Good in theory…

That might be an interesting idea, but there’s a major flaw in the reasoning. And to illustrate that we have to – yet again – go back to the birth place of modern humans: Africa.

Yeah, hide your face. That'll make your embarrassment much less conspicuous.

Yeah, hide your face. That’ll make your embarrassment much less conspicuous.

We diverged as a separate species from Homo heidelbergensis some 200,000 years ago in East Africa. The climate was tropical just like today and the days would have been scorching hot. To protect us from the damaging radiation of the sun, we no doubt had black curly hair and dark skin, as is the case with most African populations today. In the beginning, we were all African. That’s the proper, original variant of our species. Those of us not African (or of African descent) are mutants – plain and simple.

That little fact highlights the problem with blushing as a social signal: in dark-skinned humans, blushing is more or less undetectable. And since blushing is a common trait in all modern humans (and most likely also in older forms, like Homo ergaster and Homo heidelbergensis), we must conclude that the visible part of blushing has been of little consequence to us. It’s therefore not very likely that blushing has evolved as a social signal to alert others of our embarrassment.

Blushing is supposed to be – invisible?

So blushing evolved as an invisible phenomenon. Ok, so be it. But that makes it even more peculiar. What is then the point of flushing our faces if no one can even see it?

"I might be blushing. Or I might not. And you can't tell."

“I might be blushing. Or I might not. And you can’t tell.”

I’ve already mentioned another effect of blushing, something we often think of as secondary and of little importance: heat. When we blush, our faces go hot from all the blood flushing through our skin. And this effect might be what the blush response is all about. When we blush, we get a physical reminder that we’re in an embarrassing situation and that we should probably try to avoid those in the future.

So it could be that blushing is a lie detector after all, but a personal, secret one. It could be a way for our brains to tell us that we’ve made fools of ourselves again and that we need to do better in the future. After all, it’s not a problem being a liar as long as you don’t get caught. The blush response might aim to make us better liars rather than stopping us from lying. It might be our personal trainer helping us becoming highly functional sociopaths.

This whole chain of reasoning highlights a very common pitfall in our culture: extrapolating features and phenomenons displayed in one sub-population (our own) and applying them to the whole of the species. With the blush response, it seems like we’ve succumbed to the temptation once more. Man, is my face red.

P.S. Turns out my face was to become even more red. As Jim kindly pointed out, I made a couple of embarrassing typos in this post. Don’t worry, they’ve been rectified. But the whole episode sure altered my facial colour. Not that that would have any evolutionary significance.

P.P.S. I was just informed that comments and pingbacks had been switched off. This was most unconsciously done, I assure you. I always welcome your comments. (This post is quickly becoming the most embarrassing I’ve ever posted.)

7 Comments leave one →
  1. 15 December 2013 18:52

    I think it’s ironic the blush post made you blush. IRONY AND SCIENCE!!!

    I think this is excellent sciencing. I blush for a variety of reasons; not just embarrassment, but also when I’m very angry or upset. So that would hold to your theory – it’s my body telling me to avoid situations like this in the future. (Which I try to do, but you can’t always avoid crazy situations. Especially if you’re me.)

    I like being a mutant. I hope my mutant superpowers come soon. I will be an excellent X-man.


    • 15 December 2013 19:10

      It is ironic! I had no idea I was so useless at blogging.

      Yes, that’s true. It’s not just when caught lying but also other socially stressful situations. So it’s basically a “Don’t do this again, you fool!”-system.

      Yes, we’re mutants, you and I. And any other non-African people. No superpowers though. Sorry.


  2. 26 December 2013 17:16

    I love this post! Very informative! I blush VERY easily and I hate it. Or maybe I just lie too much?


    • 26 December 2013 22:11

      Aww, thank you! I’m glad you liked it.

      Perhaps you just lie badly? Practice and become a professional liar and take up a career in politics. There’s money to be made there, I’m told.


  3. 13 January 2014 22:35

    Heh. It’s interesting to think of the implications of honesty being hard-wired into our brains. Then again, It’s also interesting to make note of the differences between people who do and don’t blush in a given circumstance. For example: reviewing pictures (or worse, videos!) of a drunken karaoke night, one friend could be mortified and the other could just shrug/laugh it off. What makes one react and not the other?

    … Such are the thoughts of someone who blushes far too frequently.


    • 13 January 2014 22:42

      Yes, that is interesting. And I don’t really know the answer, although I suspect it’s a combination of differences in both physiology and psyche. Sons people might be genetically inclined to easily blush and others might have learned to be embarrassed more easily. Or even both at the same time.



  1. Beyond the Blush | Beyond the Blush

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