Is a 25-Year-Old’s Brain Mature?
Lizzie O’Leary, John Willis: Good afternoon, Chief Justice, Your Honour’s, and may it please the Court. My name is John Willis, Manassas and I, along with co counsel Jessica, Assemblyman and Garrett Burton represent Keemo Parks. You’re listening to a clip from the Michigan Supreme Court, specifically a case from March of last year about a young man, Kimmo Parks, who was serving mandatory life without parole, something his attorneys argued was cruel and unusual. Chemo. Parks is currently spending the rest of his.
Manassas: Life in prison for the act of passing a.
Lizzie O’Leary, John Willis: Gun to his cousin.
Manassas: And codefendant to Cleavon Harris.
Lizzie O’Leary, John Willis: The shooting happened in Flint back in 2016, when Parks was only eight years old.
Manassas: And one night he was out with his cousin and his cousin asked him to hand him the gun and handed it to his cousin and his cousin ended up murdering someone.
Lizzie O’Leary, John Willis: That’s journalist Jane C, who Jane wrote about the Parks case because it’s at the center of a landmark decision by Michigan’s Supreme Court. The decision said people under the age of 19 cannot be sentenced to mandatory life without parole, raising the cutoff age from 18.
Manassas: And what’s noteworthy about that case is that many scientists and neuroscientists, psychologists signed on to this amicus brief that was trying to argue for raising that mandatory age cutoff.
Lizzie O’Leary, John Willis: These scientists argued that the 18 year old cutoff was arbitrary and inconclusive because at that age, Parks’s brain and the brains of other teenagers were still developing. It’s really interesting because in that brief, they say from a scientific perspective, a person’s 18th birthday is not a rational dividing line for justifying life without parole or similar sentences because the brain continues to develop and change rapidly. And it felt like this case was huge for an intersection of science and also how we make policy in this country.
Manassas: Absolutely. And I mean, if you want to think about what is the legal age of adulthood, obviously it’s 18. We as a society kind of have just decided that it’s 18. But a lot of the brain science that’s come out over the last couple of decades have shown that, you know, our brains continue developing well into our twenties. Really. You know, your brain never really stops developing basically what input it gets. It kind of has to to make sense of. So your brain is always changing.
Lizzie O’Leary, John Willis: Today on the show. If our brains are still developing, when can the law treat us like adults? How the new science of brain development isn’t just changing policy, but how we live. I’m Lizzie O’Leary and you’re listening to what Next, TBD. A show about technology, power and how the future will be determined. Stick around.
Lizzie O’Leary, John Willis: If you do a Google search for brain maturity, you very quickly encounter the number 25. As in our brains mature when we reach 25. It’s one of those weird nuggets of pop science that’s often taken as fact and gets repeated all over the place.
Manassas: The brain doesn’t fully mature until you’re 25. You just think of it differently. As you get closer to 25, I find I feel different, like I’m enlightened or something.
Lizzie O’Leary, John Willis: It’s your frontal lobe. It’s developed now. But Jane says it’s not entirely clear where this idea came from.
Manassas: As far as I could tell, it seems like it kind of appeared. And then we just started repeating it because it felt good. So I actually asked a bunch of neuroscientists this question. I asked them, how strong is the science that, you know, 25 might be some kind of turning point. And everyone I talked to said that, yes, there’s a ton of evidence that our brains continue developing into our twenties. But 25 as a round number, there’s not really any particular thing that happens at that exact age. In fact, one of the neuroscientists I talked to said essentially, I don’t know, maybe because it’s a round number, it’s divisible by five. I’m not sure.
Lizzie O’Leary, John Willis: Part of the answer might come from functional MRI eyes or fMRI. MRI technology was introduced in the nineties and became widespread about a decade later. A regular MRI might take a picture of your body, your brain, summarize or like movies, movies that show different kinds of activity that does in fact vary with age.
Manassas: At the time, neuroscientists were saying that it was the most exciting thing that had happened in their careers, that it was going to revolutionize science. And in many ways it has. I think the major thing is that MRI allowed for types of brain science that just weren’t possible before. We are able to just put people in a scanner and try and figure out what’s happening in their brain in real time as we ask them to make decisions, as they’re watching things, as they’re listening to things. We also, as the technology improved, were able to get a better baseline of what people’s brains look like over time at different ages. I think just having that built up repository of information really helped us understand how does a brain develop in an individual, but also how do brains kind of in aggregate tend to develop over time?
Lizzie O’Leary, John Willis: But Jane says that as fMRI grew more popular, we began to oversimplify what they could actually do.
Manassas: The idea of an fMRI is, you know, this is a scan of the brain. This is hard evidence of what is happening in the brain. But f MRI, like most technologies, requires a little bit of analysis and interpretation. It’s not just like you take a picture, you develop the picture. Here’s the picture. It’s essentially a bunch of data that’s going into a computer. And scientists have to figure out how to crunch those numbers, essentially. And I think as a result, people just kind of have this idea of neuroscience is unassailable. And I think that that has also really played into this idea that there’s a point that we can measure brain maturity.
Lizzie O’Leary, John Willis: If you took, you know, fMRI of a bunch of teenagers trying to make a decision and a bunch of 30 year olds trying to make a decision, would they be appreciably different?
Manassas: Depends on what you’re looking at. But most of those studies tend to look at a part of the brain called the prefrontal cortex. And they have found that if you are looking at a teenage brain versus an adult brain and you are kind of asking people to just make a straight up decision, like a fairly straightforward decision, there’s not a ton of difference. Where you really see difference is if you are inserting some kind of strong emotion or distraction. And in that case, you find that teenagers brains tend to do a little more poorly at that than an adult brain at kind of filtering out emotion and distraction.
Lizzie O’Leary, John Willis: Is there some marker or set of markers or signifiers that says, aha, this is a mature brain? Is there any consensus on that?
Manassas: There are few things that scientists can look at. There’s this great paper in 2016 by a psychologist, Emilia Somerville, that basically made the argument that it really depends on what aspects of the brain you’re looking at and that if you are depending on what part of the brain you’re looking at and also what metrics you’re using, there is a great amount of variability and a lot of evidence that your brain is really changing. For passengers, one is not just up until 25.
Manassas: So the one thing that floored me about that paper is that if you depending on what metrics you’re looking at. Somerville had written that some eight year old brains actually looked more mature. Quote, mature. Depending on what you’re using to measure maturity than 25 year old brains. So while there is there are some established methods within neuroscience too to look at that, they’re not always all consistent with each other either. And there’s definitely not just one single way that you can look at that.
Lizzie O’Leary, John Willis: Well, that kind of seems to explode or at least deeply interrogate the idea of a of a mature brain anyway. And I guess why science is even trying to define that.
Manassas: There are lots of potential applications of one that we started out talking about with chemo. Parks’s case. I think a lot of people are looking to neuroscience in making arguments in cases where young people have been involved in some crime. But I think there’s also just this larger societal drive to talk about and redefine adulthood as our society is changing right now. So, you know, as we talked about earlier, 18 is often seen as a traditional marker of adulthood. That’s when you’re a legal adult in the eyes of the law. But if you talk to people who are 18 now, I mean, honestly, if you talk to people who like in their thirties, I think often there are many things that traditionally are associated with adulthood that young people don’t magically achieve at 18 or even, you know, at 25.
Lizzie O’Leary, John Willis: When we come back, who gets to be thought of as a teenager anyway? You wrote about this theory of emerging adulthood that seems to bracket this time of not quite adulthood, even though maybe some of the formal metrics are there and how it coalesces also with this idea of of brain maturity. What can you tell me about it?
Manassas: Yeah. So this theory was created by a psychologist named Jeffrey Arnett, and he came up with this actually back in the year 2000. So I think things were already starting to change then. But his argument was essentially that 18 didn’t really feel like this line anymore between childhood and adulthood. Rather, that other developmental period in the middle, they’re from roughly 18 to 25, where people are not full adults yet, but rather emerging into adulthood. So we called this new stage emerging adulthood.
Manassas: And of course, researchers have debated whether that’s a true developmental stage. Like, for instance, this doesn’t seem to be universal, like all around the world, but certainly here in the U.S., I think that theory gained a lot of traction because it just feels kind of intuitively true that there’s something different happening between 18 and roughly 25 that isn’t fully adulthood, but also isn’t really childhood anymore.
Lizzie O’Leary, John Willis: I saw in your writing that this seems like it’s it’s only in the West. And it did make me wonder if the U.S. and some other Western countries, like if we have the economic privilege of having this not quite adulthood period, where an 18 year old somewhere else might have to just suck it up and be an adult?
Manassas: Yeah, no, absolutely. I mean, and the privileges of seeking an education and having a little bit of cushion time to get that education before you have to launch into working full time. And of course, I’ll bracket that was saying I know there are plenty of students who are in college.
Lizzie O’Leary, John Willis: Who are working full time.
Manassas: Also working full time. But, yes, I do think that there are privileges in the West that that make that possible.
Lizzie O’Leary, John Willis: Well, this sort of brings me back to where we started thinking about the real world applications of neuroscience and the way neuroscience is applied in the law and in policy. And I wonder if it strikes you as problematic at all that this very nuanced and changing science is is being used to set what can be kind of cut and dried precedents.
Manassas: It’s hard, right, because science is something, like you said, that is constantly changing and we’re learning new things all the time. And law is more rigid, essentially. You can do this thing or you can’t, or at this age is when we apply something different. And it feels like fundamentally these two things are somewhat incompatible. But those are the two systems we’re working in. And there are scientists who are really trying to make the best of it and to make sure that people in the legal system have the latest science and are thinking about it. As you know, they are making new laws and also making these calls on these cases with young people.
Lizzie O’Leary, John Willis: Which leaves neuroscience in a somewhat strange place, rapidly evolving, but also working within the sticky confines of law and policy. And there are huge consequences for how we interpret the nuanced corners of neuroscience in the courtroom.
Manassas: I find that actually a lot of working psychologists and neuroscientists who are familiar with developmental work are being asked to participate in some way in these cases because they have the latest science and are able to explain it. So I think there was some disagreement, though, among neuroscientists in exactly where that cutoff is and how strong the evidence is for these various cutoffs.
Manassas: So universally, everyone I talked to agreed that though current law often draws a line at 18, like you’re not able to give anyone younger than 18 the death penalty or life without parole. But almost all neuroscientists there agreed that 18 did not feel right. The brain is definitely still developing at 18. It seems like right now the one major kind of debate is between the ages of 21 and 25.
Lizzie O’Leary, John Willis: Tell me about that.
Manassas: Some of the neuroscientists I was talking to advocated for drawing that new line at roughly 21. They felt like the evidence was robust, that the brain is definitely still developing up until 21. But after that, it’s not clear that there’s enough evidence to raise that higher. Others argue that there is enough evidence to raise that to 25. But I think that’s a conversation that we’re going to keep having for for many years.
Manassas: And what I found really interesting about that conversation that’s happening in that space is it’s not only about science. It’s clearly very much about science. But in talking to these neuroscientists, a lot of them cited public opinion and judges opinions and whether we as a society were ready to accept a new cutoff as high as 25. Some have said, you know, 21 is just going to be a tactical decision because we’re not ready for 25 yet. So we’re just going to argue for 21 until people get on board with that and then maybe we’ll argue for it moving higher again once people actually understand more of this brain science and are more open to seeing its applications in that way.
Lizzie O’Leary, John Willis: But also underscores sort of who gets to be a kid in the wider eyes of society. Right. You can often read accounts of, oh, this person screwed up so and so he’s just a kid, He’s 27, whereas you know someone else. Well, he’s an adult. He’s 18. There are a lot of racial and gender lines that get drawn here, and it doesn’t seem like the idea of sort of a who is mature is applied equally.
Manassas: No, absolutely. And I was thinking about Sam Bacon for. I have seen folks referring to him as, you know, he just didn’t know what he was doing. You’re just.
Lizzie O’Leary, John Willis: A kid.
Manassas: Yeah, just the kid. That’s something that feels like a separate issue that the legal system will need to work on. And I’m not quite sure how. But yeah, I feel like we see that over and over again. And hopefully, you know, by raising this cutoff will automatically just give some more people a little bit more of the benefit of the doubt.
Lizzie O’Leary, John Willis: The law has shifted the Roper case. Before the Supreme Court abolished the death penalty for people under 18. And and actually, in one of your pieces, you you quoted the attorney, Seth Waxman, kind of talking about brain science. It seems like we are moving, listening to you toward different goalposts. How quickly do you see that potentially happening?
Manassas: It’s a great question, and I think it is starting to move more quickly. It seems like in the last few years, many states Supreme Courts have taken notice of this brain science and have really made an effort to try and understand it and try and apply it in their work. And we’ve seen a lot of movement over the last few years, like in this Parks case, where judges are actually taking into account young people’s ages and the growing brain science around decision making at those ages and trying to apply that more broadly by either changing those cutoffs or at least just weighing that brain science in a decision.
Lizzie O’Leary, John Willis: You know, the Michigan Supreme Court outlawed life in prison without parole for 18 year olds. Do you think that sends a message to other state supreme courts? You should be looking at the science.
Manassas: Yeah. And from talking to some of the folks who worked on that case, it seems like I don’t know if it’s directly because of that case or just happened around the same time because people are thinking about it. But it seems like there are many other states where folks in the legal system are really thinking about this and considering it and actively asking neuroscientists for their input so that they understand it better.
Lizzie O’Leary, John Willis: Do you think we’ll ever have a consensus on what brain maturation is?
Manassas: I doubt it. But part of that is because I almost hope we don’t. It feels like such an individual thing, right? Like, I think about this. I know that this is a very crude comparison, but I mean, think about what maturation looks like for someone physically. Like what? What does that even mean? Your body changes throughout your life. You know, you might hit a certain point where you’re not going to grow taller, but everything else about you physically can change. I mean, in the brain as part of your physical body, of course. And that is also going to continue to change. So I think it’s a it’s a healthy thing, I think, for us as a society to realize that there’s not going to be a single point at which the brain is, quote, fully mature. And I think it’s really just up to us to define maturity rather than relying on neuroscience to try and do that for us.
Lizzie O’Leary, John Willis: Jane Sidhu, thank you so much for talking with me and for writing these articles.
Manassas: Thanks so much for having me.
Lizzie O’Leary, John Willis: Jane Sie, who is a freelance science journalist. And that is it for our show today. What next? TBD is produced by Evan Campbell. Our show is edited by Jonathan Fisher and Maya Armstrong Lopez. Alicia montgomery is vice president of Audio for Slate. TBD is part of the larger What Next family and were also part of Future Tense, a partnership of Slate, Arizona State University and New America. And if you are a fan of the show, I have a request for you to join Slate. Plus, just head on over to Slate.com Slash, what next?
Lizzie O’Leary, John Willis: Plus, to sign up, you’ll get this show and all your Slate podcasts ad free. All right. We’ll be back next week with more episodes. I’m Lizzie O’Leary. Thanks for listening.
