Why do humans underperform under pressure?

There doesnt have to be. If we look at organisms as some kind of model with parameters that produces environmental state transitions (i.e. we act on our environment to change it) we can evaluate that model in terms of both accuracy and complexity (cost). It means the best models might not necessarily be completely optimal because it balances out the cost (that eventually equating to a metabolic cost?) To produce optimal behaviour. Our behaviour doesnt necessaeily have to be perfect therefore and thus require an evolutionary reason per se. Tbh though the misperformance under pressure might also be an overgeneralization of some form of behaviour. I suspect that under pressure the brain might modulate how it uses its resources (e.g. executive function, prefrontal cortex) to try to optimise a speed-accuracy trade off. In a dangerous situation speed might be of the essence. Or it may just be redirecting resources to your own anxiety.

I think people underperform under pressure because their noradrenaline transmission increases beyond "stress" and into anxiety or panic.

Coupled with increased dopamine from your focused state you begin having intrusive thoughts and this forms a loop, making relaxing from your "panic" very difficult.

Adrenaline makes more blood being pumped in your legs and your arms and less in your brain and internal organs so that you can outrun or tear apart your enemy.

"Why am I failing?", asked the meme poster.
"Git, gud.", quothed the skeleton.

>this
You can often do better because faster heart rate and higher blood pressure, but this has its negatives in many situations. The high blood pressure is caused by diverting blood from capillaries to major organs, in this state the body can withstand cuts and bruises much better although it can't really run faster and only increases mental processing speeds at the expense of accuracy. If you are smart you can leverage this on tests to produce less errors, but I do this by checking and rechecking very quickly and realizing that my overall accuracy is lower per problem but I can work problems quicker if I double check work constantly while solving the problem. Although I have a much stronger stress reaction than most people, almost like a panic attack but can control it. This is just purely useless evolutionary, but on average as a species its better to ruin a few humans with a ridiculous stress reaction than have humans on average not take threats seriously and die needlessly.

When in fight or flight mode, and your brain perceives that you can escape (i.e. an exam) the adrenaline fucks up your higher brain functions, but if you've ever been in a real life or death situation everything becomes very very clear.
Source: me when I was attacked by a pack of niggers

Idk man I do some crazy shit under pressure not like suck a dick but like do a backflip or sing some Frank Sinatra, you must be doing it wrong. I've saved my own life and could definitely save someone else's and desu it's the only time I'm comfortable like I'm edgy as fuck unless I'm in the middle of a fire then I'm cool as a cucumber probably cuz my parents hated me and were really scary idk also goats totally freeze up

> humans usually underperform under pressure

Citation needed

Ah, they know it intuitively. Meaning they dont know jack shit.

Stress was evolved to deal with life or death situations. When your mind and body are in a life or death mode but it's only a drivers test it might hurt you. At the same time having some stress has been proven to improve performance because more energy goes to the brain.

I feel this.
I can barely explain shit. I'm a terrible teacher or tutor, but once the test question is put in front of me and it fucking matters, I remember or figure it out.
My friends fucking hate me for that, when I can't explain shit the day before a test and then ace it.

Its fight,flight or freeze natural response. Most people that feel insecure about themselves end up freezing, its important to feel confident that you can perform the task, you have to activate your fight response.

I learned in psychology that apparently stress can make a difficult task harder while stress for a relatively easier task even easier. So maybe if you crammed the night before then you will under perform in the exam due to the stress while if you did consistent study and have all your shit together then the stress acts to enhance your performance.

I used to have this problem.
Then I started smoking a bit of ganja before tests.
Anxiety gone, super focused.