You may heard that if you’re under 25, your brain isn’t fully developed yet. It's an adage supposing that individuals under 25 can’t think things through or make rational decisions, and so are less responsible than older folk. This logic has now formed the basis of official government advice, sentencing, and more.
The only problem with this fact is… it’s not a fact. Never has been. No matter how many TikTokers insist otherwise.
Why is it wrong? Well, lots of reasons.
There’s no real evidence for the ‘age 25’ claim
Despite its prevalence, there’s no actual data set or specific study that can be invoked or pointed at as the obvious source of the claim that ‘the human brain stops developing at age 25’.
It could be a misunderstanding, stemming from brain scanning studies which looked at subjects up to the age of 25. But that’s like saying sprinters can only run 100 metres at most after watching the 100m final at the Olympics. The limit is imposed by the context, not biology.
Others argue that 25 is simply a pleasing-sounding number, and the idea caught on purely as a result. Stranger myths have spread this way – looking at you, ‘we only use 10 per cent of our brains’.
‘Developing’ does not mean ‘non-functioning’
Just because age 25 isn’t some firm endpoint for development, it doesn’t mean the brain isn’t developing before then. Because it is. It’s developing after that age too, in many cases.
Exactly when ‘developing’ and ‘maturation’ ends is tricky to pin down. The human is essentially an assemblage of many different regions, of varying degrees of complexity, maturing at different rates.
But even if we focus on the frontal lobe, where all the reasoning and thinking occurs (mostly), it’s still very important to remember that brain development isn’t like the building of a house. You don't have to wait until all the walls and floors are done, the plumbing is sorted out and the electrics are installed before it can be used. Before you can actually live in it.
It’s more like evolution. There were many evolutionary species between the primitive rodent-like creatures that were the first mammals, and modern-day humans. But each of these stages was, at that point, a fully functional, successful species. There were no unworkable intermediary species, like a rat's torso on a pair of massive bipedal legs.
So it is with the human brain. Even if you believe that people under 25 aren’t ‘as good’ at decision-making as older people, it doesn’t mean they can’t do it, or shouldn’t be allowed to.
I, for example, am nowhere near as strong as someone like renowned British World’s Strongest Man competitor Eddie ‘The Beast’ Hall. But that in no way disqualifies me from bringing the heavy shopping in from the car.
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If it is true, we need serious societal upheaval
Even if it’s entirely well-intended, basing official legislation or government policy on the premise that the human brain is not sufficiently developed before age 25 sets a very significant precedent. If 25 is seen as the legal minimum where you can be trusted to think things through and make decisions, then that would logically apply to all facets of life.
For instance, countless people choose and complete their degrees and even PhDs long before their mid-twenties. Also, the UK is the only country in Europe that allows recruitment in the military of individuals aged under 18. And they must serve until they’re 22!
Football academies can accept players from age 9. And 25 is closer to retirement age for a professional footballer, as well as many other top athletic pursuits.
These are just three examples of people being trusted to make massively life-affecting decisions long before their brains are ‘fully developed’. And if we start insisting that anyone under 25 is too underdeveloped to do this, that has serious ramifications.
Let’s take it further. Suppose the argument is that your reasoning abilities must function at maximum before you can decide anything important. In that case, we need a maximum age too, not just a minimum.
Development is one thing, but there’s also cognitive decline. Because age and entropy can’t be avoided. That’s why people from middle age and later show reduced mental abilities. However, some studies suggest our cognition truly starts to decline in our twenties. This would suggest there’s maybe a window of a few months when we can be ‘trusted’ to make decisions.
Of course, this is a wildly reductionist, overly simplistic perspective. But the same can be said about the whole ‘under 25’ thing. Even if it were true. Which is mostly isn’t. And you don’t need to be a certain age to grasp that.
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