Why do humans sigh?

Why do humans sigh? Why do we feel so good afterwards?


I wish I knew.

Sorry, had to do it.

lol i figured most peope after they read this, they would sigh themselves

How about because 1. you take a big breath before a good sigh, oxygenating your blood and 2. you relax a lot of muscles, reducing tension and 3. you let go of thought/s that are troubling you, reducing stress levels?

When I sigh, at least sometimes, I actually vocalize it, kind of like I’m singing a note. And I think I heard somewhere that your voice automatically sighs at the right frequency to relax your body. On the other hand, is it just me or does that sound kind of like an urban legend?

OK, now I’m curious. I’ve done a (mildly non-cursory) scan of the medical literature, and haven’t found much on the topic of sighing.

Anybody got the Straight Dope on the Sighs?


Well, it’s not just us humans. We’ve previously established on this Board that dogs sigh. My cat sighs, too. So does my sister’s horse. Unless its something they’ve learned from us, I think we can’t just look at this as a human behavior.

Geez I sighed three times reading this thread

Well, for one thing, because of threads in GQ like this one.

But ya know what?

I don’t always feel good after I sigh. I usually feel… well, kinda helpless, and, and… and unwillingly reminded of the futility of it all…


I still don’t feel better. :frowning:

Betcha don’t feel any better, do ya?

Waiting… 57, 58, 59…

I didn’t mean for this thread to cause all of you to sigh lol

The above appears to be a demonstration that a sigh is social, a communication.

Lots of noises we make are vocal expressions of feelings. You could as easily ask why we grunt when picking up something heavy, why we yelp when we get a cut, or laugh, or make expressive noises during massages or sex.

Wordless noises were most likely the beginnings of speech, so partly communication, and partly just a natural vocalization of whatever we’re feeling.

This comment roused some random thoughts that I thought I’d share. Please don’t kill me. The paperwork isn’t worth it. We pedants are endangered.

  1. Oxygenating blood better? Forget it. I’m sure you didn’t mean it seriously, so I won’t cite a whole lot of biochemical crap about binding affinities and allosteric cooperativity. Suffice it to say that a healthy person oxygenates the blood in their lungs to 100% all day long, except during periods of exertion, and even then, it doesn’t usually drop by more an a few percent.

We docs often measure resting O[sub]2[/sub] sats (and often continuously) The most sensor is a disposable clip-on or tape-on LED and a light detector tuned to the frequency of oxygenated hemoglobin. It’s just slightly more complex than a single transistor - pennies apiece. Though essentially nothing in medicine costs under a buck after medical certification, markups, liability insurance and staff costs, O[sub]2[/sub] sat sensors rank somewhere between tongue depressors and band-aids (If that surprises you: a tongue depressor or O[sub]2[/sub] sat sensor is always a small part of a more expensive work-up or exam, while a band-aid, applied in a medical setting, is usually the end result of a work-up. Even 5 minutes of an RN’s time plus facility costs easily adds up to several bucks around here.)

Similarly, we have tens (if not hundreds) of millions of man-hours of O[sub]2[/sub] sat data from cardiac stress tests (taken with the patient on a treadmill). We have a darn good idea what a healthy person’s oxygen saturation is like. Moreover, we have extensive and longstanding biochemical data on what hemoglobin can carry under more conditions than you can imagine.

While your tissues (way at the capilary end of your vascular tree) may want more oxygen at a few moments during the day, your blood is usually 100% saturated at your lungs, which means that the only way to increase the oxygen supply is to pump more blood. Each beat of your heart does pump slightly more during a sigh, but your heart also pumps a bit slower during and after a sigh, so capillary oxygen doesn’t really change. If a healthy person’s blood could carry more oxygen at rest, it would! Healthy lungs have a lot of excess oxygenating capacity at rest.

I mention this, even though I’m sure you weren’t personally serious, because the “more oxygen” theory crops up in many other urban folklore and exercise myths, though any first year biochemstry student can grind it into dust. Laypeople rarely realize how thoroughly it’s been disproven. If you want more oxygen, you must increase the pulmonary blood flow (stroke volume or heart rate), “breathing in more oxygen” only helps people who have respiratory problems. Forget oxygen bars or [much worse] “oxygen drinks” or all the rest.

Even hyperventillation doesn’t change the oxygenation of your blood. Its effects are actually due to “blowing off” too much carbon dioxide.

  1. Relaxing muscles (or coordinating them more optimally in a relaxed state) is an excellent and demonstrable benefit. A lot of proven effects that are oversimplified as “increased oxygenation” are due to more relaxed, more efficient breathing and heart output (e.g. fewer heartbeats, but more blood pumped per heartbeat) There is a lot of data on the immediate physiological and long-term benefits of yoga, for example, and I wouldn’t want anyone to to be dissuaded by “yogaspeak” that happen to use words differently than “physiology-speak”

A third-year medical student can tell a lot about the health of a patient’s lungs asking questions like “How many pillows do they use at night?” or watching how they sit on the side of their bed. Yoga often uses terms that scientists may not like, but it’s just different words for the same type of observations. There’s nothing mystical -or humbug- about it.

  1. If you say that people automatically let go of troubling thoughts or slip into more efficient and relaxing positions and motions, you’ll get a lot of skepticism from some readers. I’d say it’s more accurate to say that many people unconsciously learn “what feels good” or “works well” in unself-conscious activities like sighing. Others don’t. For those who do, sighing may feel better. Others may feel better for psychological reasons. Other people might not feel any better. My point is that the relaxation benefit can be an entirely predictable learned behavior or response, and not an “inborn instinct” (which seems more mysterious to many). It’s really no different than the way that some people derive self-reinforcing benefits from good posture, or good sleeping mechanics, while others those benefits after training (or not at all).

I could say more, but I’m not a sadist. Thanks for your indulgence.

KP: re: me (I won’t quote because it’s an exhaustive reply): please reply exhaustively:

  1. How about the psychological effects of a deep breath if not the oxygenation factor? Also, I often experience times when I stop breathing for longer than the standard “gap” between inhalation and exhalation. After such a stoppage I need to inhale deeply to get going again. Happens while awake and while asleep.
  2. Yoga is great. So-o-o-o relaxing when the class is finished!
  3. I did a little experiment: try concentrating on something like reading and sigh in the middle of a sentence. Does your brain blank out for a bit? Kind of like going brain-dead during a yawn. This was what I was saying badly.

since i am only 15, can you sum up what you just said? anyone? lol? I can understand that it might be a form of communication.Any other theories???

Bad excuse.

Mr Doctor Fellow: I have heard that its the amount of oxygen that your brain specifically gets. Anything behind this? You seem kind of vehement on this subject IMO.

I think the mental side is not that we sigh because it clears our mind, but when we clear our mind we sigh. Sort of an aural clue to letting go of whatever is bothering us, and very likely something we subconsciously (or perhaps have it built in) to clue other people to our emotional state.

I’ve never really seen an animal sigh aside from dogs and fish. The dog probably picked it up from my other dog, who does it when she’s pissed at me.

Sighing does make a difference for ventilated patients

I’ve not seen anything that shows this same effect in healthy people breathing on their own, however.

Perhaps it is just like a yawn, you know like it doesn’t have real meaning?

Come on people keep those ideas coming!

[KP], I sleep with zero, one, or two pillows. (Sometimes I eschew the pillow and just lie face down on my folded arms). I’m really curious–what does that say about me?