Your brain works fine when you're under 25 (no matter how 'inconvenient' this fact may be)

The claim that, if you're under 25, your brain isn't fully developed, so you can't be trusted to make mature decisions, or held responsible for actions, is very common. But also very wrong.

Photo by Emily Ranquist

As I write this, there’s a lot of (valid) furore online regarding the disconcertingly young engineers that appear to be taking control of US government organisations on behalf of Elon Musk.

Regardless of the political factors behind this (utterly deranged) state of affairs, we’re already seeing comments online, from various sources, trying to defend these flying Muskees. They’re too young, you see. They don’t know what they’re doing. So we shouldn’t be too harsh on them.

Why does their age matter? Well, because, as many have claimed, your brain isn’t fully matured until you’re 25. So we can ignore/dismiss/overrule/absolve of responsibility anyone under that age, no matter what they say or do, like try to overthrow government institutions.

This stance pops up more and more often these days, in increasingly important contexts, like voting or reproductive rights, medical decisions, criminal sentencing, and more.

The notion that the under-25s lack the cognitive maturity to make rational decisions, demonstrate self-control, or understand consequences, is increasingly being viewed as an established biological fact that needs to be accounted for.

For the record, according to all neuroscientific understanding, it isn’t. It’s bollocks.

I’ve previously covered this for Science Focus magazine, and referenced it in this Substack already, but here’s another rundown, just to be sure.

“Still maturing” does not mean “Non-functioning”

Photo by Paul Sardar

The average height of a fully-mature great redwood tree is just shy of 70 metres. That’s about as tall as a 20 storey building.

Therefore, logically, a great redwood tree that’s 35 metres tall, has still got a lot of growing to do. It’s not a fully mature redwood tree.

…but it’s still a 10-storey tree! Over a thousand tons of living wood, leaves, and branches that, if it collapsed over a built up area, could easily flatten a typical terraced street.

So, if someone were to look at said 10-stoery tree and say “Nah, it’s not fully grown, so it’s not an actual tree yet”, you would have very good reason to question their intellect, their observation skills, and their ability to comprehend basically anything, ever.

But when someone says/implies some variation of “Actually, your brain doesn’t work properly until the age of 25”, they’re saying the neuroscientific equation of “A 30 metre redwood isn’t really a tree”.

Basically, far too many people have seen descriptors like “not fully developed” and taken that to mean it’s like a partially assembled Ikea bookshelf; a work in progress, something that will be able to do it’s job when it’s done, but not until then”.

That’s not how brains work, though. At every stage of development, they’re ‘functional’. Young brains allow us to walk, speak, perceive, connect, deduce, calculate, coordinate, decide, respond, focus, retain, and all the other stuff your standard human brain does all day every day to successfully navigate our increasingly complex world.

It’s just that the parts and processes in the brain change and alter and update, as we age, and experience more things. Granted, the frontal cortex, the most sophisticated part of the brain responsible for self-control, predictions, analysis, and all those other potent cognitive processes that humans are uniquely good at (usually grouped under the label “executive function”), this takes the longest to develop to peak capabilities. But that doesn’t mean it doesn’t function at all before we hit our third decade. Because of course it does.

Basically, while people under 25 might not as ‘capable’ as older adults in certain areas and abilities¹, due to a relative lack of relevant experience (which is how the brain learns and refines its abilities and performance), this doesn’t mean they’re totally incapable.

A professional weightlifter will be stronger than someone who’s just joined the gym, but that doesn’t mean the latter is so weak they wouldn’t even lift the pen to sign their name on the membership forms.

Assuming this is the case regarding advanced neurological functions in younger people is both completely wrong and, let’s be honest, deeply insulting.

The “not fully mature until age 25” notion is wrong anyway. That’s obvious when you think about it, even briefly.

All that stuff I just said? That all applies if we assume that the “your brain doesn’t function properly until it fully matures at age 25” is correct.

But it isn’t.

Why do people insist otherwise²? Unclear. But it’s not based on any particular scientific study or claim. At best, it seems to be a corruption/misunderstanding of a few older studies into brain development, ones which mentioned, or only used subjects under the age of, 25. But didn’t make any grand claims about this being some developmental cut-off point, or the moment when your brain dings like a microwave, to let you know that it’s ‘done’.

Presumably, an enthusiasm for soundbites over substance and a preference for simple answers to complex issues, led to the warping of these studies’ claims into the increasingly-entrenched belief that a brain under 25 years old cannot function like a ‘proper’ adults. Which, to reiterate, is wrong.

And it’s obviously wrong, when you step back and think about it for even a moment.

Humans spent millennia where the average lifespan was 25 years. Given how evolution works, if we kept dying before our brains were mature enough to make important decisions, our species would barely have lasted a week. And yet… here we are.

Also, the idea that our brain abilities only occur in set developmental stages has long been proven inaccurate. Our cognitive setup is a lot more flexible and variable than that.

Indeed, there are countless cultures and societies, both in history or active in the world today, where people under 25, even children, take on roles with significant responsibility, and manage fine. Whether it’s helping with the family business, working part time to keep a roof over everyone’s heads, stepping up to parent younger siblings when the actual parents can’t for… reasons. All of these are common occurrences.

You could argue that people so young shouldn’t have to take on such roles, that they’re less capable of doing them than a more mature adult, or that they’re being done more long-term harm by having to do so much, so young. All these are valid points. But none of them mean young people can’t do these things, that they’re neurologically incapable of stepping up to significant responsibilities and decisions. That’s demonstrably not the case.

People invoke ‘brain development’ to support their argument… but they really shouldn’t.

SHVETS production

Let’s be clear; more often than not, anyone invoking the ‘people under 25 years old don’t have functional brains’ argument, is doing so to support their position or beliefs, whatever they may be.

That’s why someone can be deemed too young to understand the decision to, say, get an abortion, and simultaneously be declared mature enough to have and raise a baby.

Or young men under 25 can be ‘too young’ to be expected to stop themselves from committing crimes like sexual assault, but are definitely old enough to receive the full adult punishment for joining a terrorist organisation, or entering another country by non-legal means. And so on.

Plus most of our society (although it varies by nation) is set up in a way that fully acknowledges people under 25 as essentially functional adults. You can have sex at 16, choose the exams that will define your whole life at 14, drive at 17, vote at 18, take out a massive load, get married, buy a house, have kids, all that and much more, all under the age of 25.

For the longest time, it was expected for people to do all these things done before age 25. And that is still the case for many. It’s hard to reconcile this with the idea that your average human can’t even make decisions properly until their close to 30.

And even if someone does dig in, and insists that we absolutely should only let people make important decisions when their brains are operating at maximum cognitive capability, well, have you heard the phrase “be careful what you wish for?”

Because those apparently-crucial executive function abilities that young people apparently lack? Thanks to just age and entropy, they usually start to decline in your thirties and forties.

So, scientifically speaking, someone in their sixties, or older, has a brain that’s no more functional than someone in their teens or twenties. It is likely even less so, because a younger person’s brain is improving.

Sure, someone in their sixties has undoubtedly experienced and learned a lot more, by dint of just being alive longer. But if that’s your stance, then anyone older again is even more capable, and we should all just be deferring to the oldest person in the world, while we can.

Obviously, that’s not a sustainable system in any way shape or form. Just because someone’s older, it doesn’t automatically mean they have a superior brain. But that applies for people in their twenties as much as anyone else.

Basically, there’s no neuroscientific justification for dismissing the claims, decisions, and actions of someone under 25. And “because it would be convenient for me in this case” does not make up for that in the slightest.

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You can read more about the surreal approach people have to brain development and age limits in my latest book, Why Your Parents Are Hung-Up on Your Phone and What To Do About It.

1. Although even this is debatable, in many contexts.

2. I include myself in this. You may have read other works of mine where I refer to this claim as if it’s a fact. I genuinely thought it was, it was so widespread. However, I don’t think I ever took the follow up step of going “…and therefore, we should ignore/dismiss younger people”. But do correct me if I’m wrong.