You haven’t given me a source other than Slate.
And look, if you can’t see how that argument generalises to antivax acceptance then you are part of the problem frankly.
I’m going to stop here because you’re dug in, and starting to project ad hominems.

No, because down that road of argument lies the validation of antivax views.

There is plenty of evidence for consensus. Medical institutions and departments national and international all claim that brain maturity is not reached until the mid to late twenties. Google “prefrontal cortex development age”. There very much is a consensus, unless we are using different meanings for the word “consensus”. Or perhaps we’re not talking about the same fact that there’s consensus over. If course there’s no consensus on the exact age, and that’s all the articles were saying, but that has no bearing on the fact that development doesn’t peak and fall until the twenties.

I choose to believe the consensus. It’s getting tiring saying the same thing.

You’re sources are junk, I’m afraid. They are magazine articles written to excite readers rather than get at the truth. I’m finding it hard to explain this to you without sounding patronising so maybe you should educate yourself on the veracity of source types.

So your claim is that there’s no “fully developed”? That then does not support your original assertion that we shouldn’t go easier on people who are younger for making bad decisions. They remain significantly less developed than their mature counterparts, whether or not someone in their 40s still has the potential for development (of course they do). Neural plasticity doesn’t suddenly 'switch off, but it does appear to peak and fall quite quickly in the late twenties (of course, this is not an iron rule: everyone is different). I can source this claim with any number of studies if you like.

I’m sorry I feel I picked on you a bit, really I just wanted a dialogue. I’ve seen this notion going round that “our brains not being fully developed until after 25 has been debunked” and I’ve been meaning to read into it for a while to see if it’s true. I’m going to keep looking at it, but I don’t see any evidence that scientific understanding of prefrontal development has changed. I’m a scientist by education so I am perfectly capable of charging my mind if I believe there is evidence to do so. In fact I find that process thrilling and it’s literally one of the reasons I get out of bed in the morning. I’m not stubborn or dogmatic in the slightest. But I am hard to convince. Sorry about that.

I did.
That Slate article argues that there’s nothing special about the age of 25, not that brains are still in development at that age.
If you can’t find a scholarly, reliable source for your claim that our brains are fully developed at 25, then I’m afraid you’re not going to convince me. The reason for that is this: I’m not hubristic enough to believe I know better than the field of neuroscience, and I’m not credulous enough to believe one person’s opinion that they do.
Nothing you have shown me contradicts the fact that the prefrontal cortex isn’t fully developed in people in their early twenties. In fact your latest source repeats the claim multiple times.

I did. But that link is just opinion. The studies are real science. The claim that all the research stems from it being the cutoff year is unsupported by the article in the link, which, again, is one person’s opinion. Weighted against the consensus of medical science, it’s just not very convincing to me.

So what kind of source would you accept?

https://www.nature.com/articles/s41386-021-01137-9

Although neurons of the PFC are generated before birth, the differentiation of its neurons and development of synaptic connections in humans extend to the 3rd decade of life.

https://pmc.ncbi.nlm.nih.gov/articles/PMC3621648/#%3A~%3Atext=The+development+and+maturation+of+the+prefrontal+cortex+occurs+primarily%2Cthe+age+of+25+years.

The development and maturation of the prefrontal cortex occurs primarily during adolescence and is fully accomplished at the age of 25 years.

https://www.nimh.nih.gov/health/publications/the-teen-brain-7-things-to-know

The brain finishes developing and maturing in the mid-to-late 20s.

It seems to me that there is a scientific consensus on the subject.

So I agree it shouldn’t be used as an excuse, but in a perfect world it would definitely be grounds for diminished responsibility. If your brain hasn’t fully developed its decision making centre then you aren’t on a level playing field with those whose have. And it’s a fact that full development of the prefontal cortex doesn’t occur until mid to late twenties. They’re just not at the you-ought-to-know-better endgame, neurologically.