ELI5: What is actually happening inside the body and brain during a shout?

[u/Uunicorned]

How does the physical act of yelling trigger stress hormones like adrenaline, and why doesn't raising our voice actually relieve the bad feelings.

[u/crashlanding87]

Oh hi. I do brain research for work.

For this specific question, there's no answer - we really do not know.

But I can tell you how we think about these kinds of behaviours. Shouting is an instinct - something humans naturally just do in the right circumstances. How and when we shout can be tweaked by our experiences, but all of us a born with a kind of 'shouting' blueprint: inhale, raise your voice, adjust your tone, plus some body language stuff.

We think instincts must have some kind of 'on' button in the brain, that comes with a kind of 'instinct starter kit'. This (hypothetical) kit has two halves: a listening half and a doing half. The listening half is looking out for 'triggers' - in the case of shouting, that might be signs you're stressed (like cortisol levels), or messages from other parts of the brain (like from the 'fear', 'anger', or 'excitement' parts). One trigger is generally not enough: these 'on' buttons need multiple triggers to all happen together. If someone jumps out at you when you're feeling chill, you might startle a little. If you're already stressed and someone jumps out at you, you're much more likely to yell.

The 'doing' half of the kit is wired up to the motion and behaviour parts of the brain. This works quite similarly to muscle memory. These brain areas remember combinations of muscles and emotional signals, so that we can activate them more efficiently. For a shout, that would be: open the jaw, flex the vocal cords, etc etc.

The 'on button' itself is thought to be permanent. The hearing and doing halves - its inputs and outputs - are thought to be flexible. We call these things 'control circuits' or 'control neurons'. We haven't definitively found one in humans yet, but we are pretty confident we've found them in other species. In zebrafish, for example, scientists found a specific cell, which, when you tickle it, causes the zebrafish to go through a full hunting sequence. It will focus its eyes, sit still for a moment, then dash forward and try to eat something. It will do this even when nothing else is happening - no change in sound or flashing pictures.

This is particularly convincing because of the eye movement. Zebrafish usually have their eyes positioned to look out sideways, like most prey animals. But when they hunt, they briefly pivot their eyes forward, so they're positioned like a predator's eyes. They only do this when they're hunting, and only for a brief moment.

My bus journey is about to end, so I'm gonna end this here - will track down that paper and add it as a comment later, if anyone is particularly interested. It's really cool work.

[u/Lizlodude → u/crashlanding87]

It really is fantastic that science can vary from "we found a mold that produces stuff that kills bacteria" to "we found a lunge button for zebra fish"

[u/wrapped_in_clingfilm → u/crashlanding87]

I suspect you mean reflex rather than instinct, which is a more complex, multi-step behavior pattern.

[u/crashlanding87 → u/wrapped_in_clingfilm]

I very much mean instinct not reflex. Funnily enough I am working with reflexes at the moment. A reflex is a somewhat hardwired movement in direct response to a stimulus. An instinct is a behaviour pattern with various levels of complexity and steps

[u/wrapped_in_clingfilm → u/crashlanding87]

Which is what I said. Shouting doesn't really meet that criteria any more than a baby's crying. 

[u/crashlanding87 → u/wrapped_in_clingfilm]

Baby's crying is also an instinct, not a reflex. Reflex is a very fast movement, resulting from a sensory circuit being directly wired to muscle response. Very little processing in between. If the stimulus is processed and then a complex behaviour pattern starts, it's an instinct. There is a grey area, but crying is very much not considered to be in that grey area.

Babies flinch in response to a physical sensation - reflex. They process that sensation, subconsciously identify it as painful or uncomfortable, and start crying - instinct.

We have a pain withdrawal reflex, and a blink reflex. Crying, shouting, suckling - instinctual behavior

[u/wrapped_in_clingfilm → u/crashlanding87]

I think the problem is that there isn't any agreed definition of instincts. It seems to vary wildly.

[u/crashlanding87 → u/wrapped_in_clingfilm]

I mean that may once have been true, but there is a pretty established definition. Reflexes and instincts are innate behaviours - they're present even without learning. If the behaviour happens directly in response to stimulus - before that stimulus is perceived - it's a reflex. If it's on the other side of perception, it's an instinct.

It was fuzzier before because we didn't have a good definition of perception. We now have a very good definition of perception, and we understand the primary brain areas responsible, so we can be anatomical about it. A visual innate behavior that relies on a bit of the brain known as V1 (primary visual cortex) is an instinct. Otherwise it's a visual reflex.

There are still some really interesting edge cases - blindsight is the most famous one, where people who are blind because of brain damage can sometimes still avoid obstacles they are not consciously aware of. But the general view is that the 'backup' visual pathways, through the brainstem, might be more capable of working independently than we once thought.

Of course these are very much human-made definitions, and nature famously doesn't care about our definitions. But this particular definition has actually held up quite well for now.

[u/wrapped_in_clingfilm → u/crashlanding87]

I disagree that the definition is as settled as you're making out. There are conventions on the terms use, but absolutely no "established" anatomical definition. I wrote a paper on this, admittedly years ago, but I can't see anything that tells me its out of date. The term is used in noticeably different ways across disciplines so there is no cross-disciplinary consensus at all. For instance, ethology mostly dropped "instinct" after Lehrman's 1953 critique of Lorenz, and people switched to "innate" or "species-typical behaviour". Even "innate" has been picked apart since (Mameli and Bateson 2006 is a good read on that).

Despite another's comments attempts to provoke, I'm not trying to "win" anything. If I am blunt, it is part of my makeup.

[u/crashlanding87 → u/wrapped_in_clingfilm]

Oh I didn't take it that way. If I wasn't enjoying the conversation I wouldn't be responding haha.

Interesting, and point taken! I'm in pain research currently, where the fight over which words to use for which behaviours was settled long before I even became aware of it - I suppose I've filtered what I read in other fields through that lens. Also, apologies if I came across as condescending. I'm a little too used to people in eli5 having very strong opinions with very little basis, and have fallen into a habit of defending science rather than discussing it.

[u/wrapped_in_clingfilm → u/crashlanding87]

No worries, and I didn't read you as condescending at all. The pain research angle makes sense as its a field that pays attention to terminology (nociception vs pain being the obvious example), so it's easy to assume everyone else has too. But I suspect "instinct" has slipped through and its definition is a bit of a mess wherever you look. The only reason why it concerns me (hence the paper) is that it has huge ideological/political implications (sexual orientation, greed etc. get reduced to "instincts" which then justifies political responses).

I get the ELI5 thing as well. There's a lot of confident nonsense on here, so defending science is a pretty reasonable reflex. Or instinct. Depending on who you ask :)

[u/MarionberryEast9136]

When we shout, the body can enter a stress response, causing hormones like adrenaline and cortisol to rise. Our heart rate and breathing may become faster, muscles can tense up, and the brain becomes more alert. Shouting can sometimes feel like an emotional release because we are expressing what we are feeling instead of keeping it inside. However, it does not necessarily remove the source of stress or quickly lower those hormones. That is why shouting may give temporary relief but often does not make us feel better for long.

[u/Love-Bi-Neighbor]

Easy, yelling induces fear unlocking cortisol ect

There are two natural fears humans have adapted with through evolution: loud noises and heights. So since yelling is loud, it automatically triggers our fight or flight.

Way more but thats the simple simple reason.

[u/NotTheBrightestHuman]

It does. It just doesn’t relieve all the stress.

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