A delightful study on the function of sighing has just been published in the journal Physiology and Behavior which suggests that our wistful deep breaths reboot our respiration and work as an unconscious stress management strategy.
Researchers, led by psychologist Elke Vlemincx, asked participants to wear devices that kept track of their breathing and monitored chest muscles while they were asked to complete stressful pressured mental arithmetic tasks or an attention task that required similar bodily movements but without the mental stress.
The participants thought they were completing an experiment on the body’s responses to maths problems but, in reality, the researchers were looking at the effect of sighing. Researchers kept track of spontaneous sighs, but in the second high pressure maths task, the volunteers were asked to deliberately sigh.
In biological systems, adding a little randomness or noise can sometimes make a signal clearer as long as it doesn’t drown everything out – a phenomenon technically known as stochastic resonance.
Imagine you’re in a dark nightclub trying to make out people’s faces. Too little light doesn’t help, completely crazy lighting is just too dazzling to allow you to recognise anyone, but moderate disco lighting, even with the colours and movement, does allow you to identify individual faces among the crowd.
The same principle applies when the body is signalling to itself, of course, and the researchers suspected that sighs might work like a bit of added noise into the breathing system, allowing the internal breathing regulator to get back into its groove.
As it turns out, sighs do seem to work like the brain’s reboot button for regular breathing. During mental stress, the volunteers’ breathing became more and more irregular as participants increasingly relied on deliberate breath control, at which point, a sigh occurred, causing automatic regular respiration to kick in again.
Furthermore, muscle tension steadily built up before a spontaneous sigh and decreased afterwards, supporting the idea that sighing helps release tension.
Interestingly, when the participants were prompted to sigh by the researchers, muscle tension decreased by a much smaller amount and breathing become more irregular. Being instructed to deliberately sigh seemed to actual impair recovery from mental stress.
It’s a wonderfully elegant study because it helps us understand both the mental and physiological function of a behaviour usually associated with wistful distraction.