The Psychology of your 20s - 412. Does your frontal lobe ACTUALLY develop at 25?

Episode Date: May 2, 2026

Where did this myth that our frontal lobe develops at 25 actually come from? What does the death penalty and Leonardo DiCaprio have in common? You've probably seen TikToks, videos, tweets, memes, but what is the truth about brain maturity? That is what we're breaking down today, including:  Why brain development is a lot more complicated than a number The specific role of the frontal lobe  The early 2000s research that defined how we see brain development  Why our brain actually develops in spurts  The good news for 20 somethings  Happy listening! Watch on Netflix: HERE Follow Jemma on Instagram: @jemmasbeg Follow the podcast on Instagram: @thatpsychologypodcast Subscribe on Substack: @thepsychologyofyour20s For business: [e-mail] See omnystudio.com/listener for privacy information.

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Black Effect Podcast Network on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. Hello, everybody. I'm Gemma Spike, and welcome back to the psychology of your 20s, the podcast where we talk through the biggest changes, moments and transitions of our 20s, and what they mean for our psychology. Hello, everybody. Welcome back to the show.

Welcome back to the podcast. It is so great to have you here back for another episode. In fact, back for a special little bonus episode from me to you, just for my OG audio listeners. You guys know the drill with these smaller episodes. I feel like there are some topics that are so, so interesting, but also deeply understood. However, they just don't warrant like a full 30 to 45 minute episode. There's like only so much that I can ramble on, only so many tangents that I can go on, unfortunately. but I still want to talk about them. I still want to talk about it. I still think a lot of it

would be interesting, not just for me to research, but for you guys to hear. Today's episode is one of those topics because we are talking about frontal lobe development. And the recently, I would say recently, like insanely popular idea that our frontal lobe only fully develops at 25. And kind of the reasoning that therefore, you know, we can't really trust any decisions that we make before then. We don't really know who we are until then. And the sense that, you know, you wake up at 25 and suddenly, like, the world just makes sense. Suddenly, like, this is when real adult life begins. I've seen so many people online describe this, like, almost like a sensory feeling of what it feels like to turn 25 and to experience this like seismic shift in their identity and maturity

almost all at once. And I definitely don't doubt that they're experiencing this. I think I've also felt this way in recent years. It's just not as clear cut as you would think. And it turns out that frontal lobe development age that everybody talks about actually comes from some really, I don't want to say dodgy misrepresented research from like 20 to 30 years ago. And it has since been dissected, dismissed, and kind of revealed to probably not be very accurate. So let's talk about it. Let's begin by actually discussing like what the frontal lobe does. Like why is this part of our brain so essential for essentially determining.

that somebody is mature or determining that somebody's brain is fully developed. So your brain has a few lobes. You've probably learned this in like high school science class. It has four lobes, the parietal, temporal, temporal, occipital lobe, and of course the frontal lobe. You can also include the insular and limbic lobes as well if you want to get really technical. If you want to be, really want to impress people, you can say it's six lobes. But the theory essentially goes that each lobe is responsible for different functions and behaviors. Now, even this theory, I have to say, that theory in itself has been hotly debated because I think we now realize, like, the brain is a highly integrated network of cells. It's not like there are four or six little brains in our brain. You know, it's one brain that every area of our brain is constantly communicating. If you were to look inside the brain, like, you wouldn't see any physical walls dividing the different regions. Like, the functions definitely overlap. But,

yeah, there's definitely different things that each lobe does. And the frontal lobe, especially, we definitely know, is deeply responsible for attention, for reasoning, for memory, for identity, and most importantly for this episode, for executive functioning. So executive functioning basically just means your ability to exert control over your actions and impulses and to just, like, think through your decisions, think through your emotions, think through a situation in of you and like come up with a clear idea of what is best for you to do and how to execute that. Now if that area of your brain is, let's say, injured or not developed or underdeveloped, not at its full capacity yet, the logic basically follows that we would have a lot of difficulty

performing those same attention, reasoning, memory, executive functioning functions as well. And basically this would explain why, you know, before the age of 25 as this theory goes, before this area of our brain isn't developed. That is why we make stupid decisions. That is why we text our ex when we know we shouldn't. That is why we make random, spontaneous life choices. That is why we do highly irrational things. That is why a man who was 40 dating somebody who was 22 doesn't make sense,

which literally, yeah, probably true. Actually, absolutely true. And I think there's like parts of that theory that are very comforting, right? because we all do really stupid things in our early 20s. Like, I cannot tell you how many times I have bleached my hair blonde and then dyed it black and then bleached it again and then died it black. And I've cut my bangs a few too many times without ever really thinking it through. Those are just some examples. And, you know, the older I've gotten, the more I, you know, those impulses have kind of lessened.

But does that all happen or did that all happen the moment I'd turn 25? No. And that's because the 25 thing, as I've kind of already revealed, is a myth. And it sometimes becomes a bit of a self-fulfilling prophecy where we definitely feel like we now are adults after that age. But really, that's just the feeling that we are getting from the popularity of this number and from the popularity of this narrative, the narrative behind it isn't actually true. And this is where we need to talk about where this number came from, because it didn't just magically appear what really happened and what it all stems from is this singular study that was done actually I lie not a singular study it was a couple of studies there was one done in 1999 and one done in 2004 by the same group of researchers that looked at brain development from childhood to adolescence particularly what they were looking at was increases and decreases in gray and white matter gray matter is responsible for a lot of thinking, like it's called the thinking matter and decision making. And white matter is kind of what

carries the messages between the different lobes or parts of your brain. So if you were to see like a cross section of a brain, it's, the white matter is a lot of the stuff in the middle. And in these studies, they wanted to know when our levels of white and gray matter, like reached peak maturity. And so they scanned hundreds of brains, hundreds and hundreds to figure this out. And out. Here's the catch, though. The oldest subject, the oldest person whose brain they scanned, how old do you think they were? 21. They were 21 years old. I think there was a couple of other studies around that time that had a couple 22-year-olds, a couple 23-year-olds, but those most prominent studies, firstly that one in 1999, and then the very famous one in 2004, the oldest

participant was 21. So where did that 25 number come from? This 25 number that came from this research, well, it came from the author of the paper called J. Geard. I don't know if a G-E-E-D-D, it's G-I-E-D. And he basically speculated and he said, well, I guess it would be 25. If we wanted, based on our research, if we wanted a guess when the brain fully developed, I would say 25. Literally, this is exactly where this comes from. He does this research. He goes and gives a bunch of interviews about this research. And in an interview he does with Time magazine, they ask him, you know, based on what you've been seeing in teenage brains and children's brains and adolescent brains and young adult brains, when do you think the brain fully develops? And he quote, he says, if I had to pick a number

right now, I'd probably say 25. Now that number stuck because of what a prominent interviewer was. The reason it was really prominent was because at the time, this was in America, they were debating the death penalty and basically like criminal implications for teenagers and for people in their early 20s in the US. And whether people who were 17, 18, 19, 20, 21 could be deemed responsible for their actions given this theory that their brains probably still reflected those. of teenagers. And, you know, why could it... It was basically like, why would somebody who was 15 not be given the death penalty, but somebody

who was 17 be given the death penalty or somebody who was 20 being given the death penalty when, according to our research, like these brains, the brains of these individuals look really, really similar. So it was a huge news story, right? It was a massive news story, and that is where the 25 number comes from.

This interview that this guy did, this interview that Jay did, where he said, if I had to choose a number right now, 25, despite the fact that their study did not include anybody who was 25. And specifically to hone on this, like why was it the frontal lobe specifically that develops at 25? Why not the whole brain? Why was there such a focus on this? That is because from that same research, the same scientist discovered that it was the frontal lobe that developed loss. So it just kind of made sense. You know, the frontal lobe was the last piece of the puzzle. When frontal lobe development was done, they said brain development was done.

You know, when the frontal lobe clicked into place, that's when people could be seen as responsible. You know, emotionally, morally, most importantly, criminally. So that is the origin of the myth. I also think that there is something to be said about the fact that 25 is a really nice number, right? 25 is a very solid, clean, neat number. And that attracted a lot of attention. You know, he didn't say 24 years and 11 months. He didn't say 26 years and four days.

He didn't even say 25 years and one, I don't know, one quarter. He gave us one simple, neat, attractive number. And people love that kind of certainty and that kind of simplicity when it comes to describing something as confusing and complex as brain developed. It is the same reason why the myth that we only use 10% of our brain is so popular, because 10% is a nice simple number. Same with the myth that people are 90% water. Simple number. The thing is, actually pinpointing when the brain develops for real is incredibly, incredibly difficult because it differs from person to person based on genetics, based on environment, based on experiences, even based on exposure to things like alcohol.

it's also gradual. Yes, like there is a point where your brain will reach peak maturity. But it's kind of what we call like a bold man conundrum. I don't know if you've heard this like this kind of exercise before, but essentially there's this like debate around how many hairs does a man have to have before he's no longer bald? You know, if there was a man in front of you and he had one hair, one single hair, you would think he was bald. What if he had five hairs? Probably or bald? What if you had 500 hairs? You know, there is a point at which one additional hair stops that man from being bald. And I know that sounds like a weird analogy for brain development, but there is a point where one slight neural change takes somebody's brain from not developed to

developed. So that's like the interesting thing. That is going to be different for everybody. The other thing is that the brain continues to change across the lifespan. New paths are constantly being paved, old paths are scrapped, we lose and gain white matter due to learning and changes in our lives. So is our brain ever fully developed? Yes, but is it also constantly a work in progress? Also, yes. Like, what does development really look like? Like, what does that peak look like? This is what the science says these days. When is our brain fully developed? Actually, just last year, they kind of got as close as they ever have to answering that question. and they did it in the most roundabout confusing way possible because of course they do.

The study was called, the study that kind of concluded not once and for all, but pretty solidly what is actually happening, is called topological turning points across the human lifespan. It was a study conducted out of Cambridge. If you follow me on Instagram, you may have seen me talking about this study recently, but essentially these researchers analysed the brain scans of more than 4,000 people from infancy, all the way up to 90 years old. So no, they didn't just stop at 21. And they specifically looked at white matter changes. Here is what they found. Your brain basically has several spurts or key periods of development across the lifespan. And in each of those periods, different things are occurring.

The four turning points that we need to know are ages nine, ages 32, age 66 and age 83. So between zero and nine, your brain is just like building as much as it possibly can. It's growing very, very rapidly. Between nine and 32, which they actually, they call the adolescence period, even though it's not just the teenage years. That is when your brain starts to prune. It starts to build different neighborhoods of neurons and thought processes and it integrates those neighborhoods. It gets really, really organized. It starts to kind of get closer to optimizing and gets closer to being able to reason through all of its thoughts. But, Between 32 and 66 is when it gets the most efficient and it begins to specialize.

Basically, things start to really feel locked in. That's when we're perfecting pathways. After 63, the core areas of our brain and those core pathways become more important. All the other, like, kind of medium and small important pathways around and different circuits become less important. So basically, it's organizing and it's consolidating even deeper. And after the age of 83 is when we see a lot of. of neural decline, loss of gray and white matter, and it's when we see central pathways really become the main pathways. So if you think about it, like almost like the building of a society,

zero to nine is when like everybody's like pitching tense, like everybody's just trying to figure out what's going on, like there's all these disparate areas, all these different regions and like they're not very connected and it's like kind of rudimentary. Then like that second period, nine to 32 is when, you know, we start building some roads between the towns. Like, things start to get a bit more coherent. 32 to 63 is when like, yeah, we've got major buildings going up. We've got a highway. We've got every, all the structures like are good to go after 63 to 83.

It's like, oh, you know, people kind of, you know, we're getting, like, the people kind of moving out of town. You know, they don't really use all those little suburban streets we built for them. It really just me, they use like, you know, a couple of main roads. and 83 onwards is like the town is now bypassed by a highway. There's like a couple of roads that run through. Those are the ones that are used. All those little disparate neighborhoods are no longer really supported.

That's like the best way I can think of explaining it. What the study basically found is that there is not one final age we land at and we are good to go. We are changing in different ways across our lives based on our neural and environmental and social and emotional and mental needs. It also says that, you know, if you are in your 20s right now, which I'm pretty sure you are, I'm going to take a well-informed guess considering you're looking or you're listening to this podcast, don't feel like you are locked in. Like, you will continue to be in a state of exploration and change and growth until your mid-30s.

And then after that, you will continue to be in a state of optimization until your 60s. If you're in your mid-20s and you're waiting for that epiphany that comes with your frontal lobe developing for good, you know, you may have to wait a little bit longer. That is a good thing. What this study also talked about is how much we are at an advantage during this period to shift and change and really influence, you know, what pathways are strengthened and which pathways are abandoned. So you need to make the most of your brain right now by giving it as many experiences and learning opportunities as possible because you are in your prime. You are building the society of your brain. I also think it's scary in some ways. Obviously, it's scary to be like,

oh my God, I've got to wait a little bit longer. And also, oh, my God, it's scary to think that after 32, I can't make as many changes as I could now. You can continue to make changes. There is no magical switch. You get to keep learning, keep developing much longer than you probably anticipated. And obviously, like, the older you get, the more you will start to make more informed decisions. and the more you'll be able to feel like you have more control over your life. So I think all of this is actually a good thing. As long as you are feeding your brain newness and novelty and even like actually engaging in the spontaneity of this time in your life,

I actually think you're totally winning. Of course, like after 32, we can still continue to do that. We still will make dumb decisions. But I think the same drive and impulse won't be there. And that is a huge perk of being young. your willingness to explore and to take risks and just to follow impulse and follow desire and follow passion is a huge part of this period that you're in right now, not just in terms of your life, but in terms of your brain development. So there you go, guys. This is the frontal lobe

myth decoded for you. Next time somebody like makes a comment about it at a party or like makes a meme about it online, you know, you can be that annoying, no at all, who corrects them, or at least like the person with the fun fact that, hey, no, your brain does not, or your frontal lobe does not fully develop at 25. You got at least seven more years before that takes place, maybe even longer. I hope you enjoyed this little bonus episode. I'm not going to ramble or rant for much longer because I want to keep it short and sweet for you guys. Yeah, I hope you enjoyed this episode. I actually had so much fun researching it. I feel like some of my favorite episodes and where we get to myth bust, like, certain psychology things, because it's, you get to go

into so much, like, history as well, like the history of the death penalty in the US. Who would know? Who would think that the death penalty in the US and Leonardo DiCaprio memes would have the same origin point, which is this one study done in freaking, in the early 2000s. So, there you go. Fun fact to end or start your day with. Make sure that you are following us on Instagram. Make sure that you, if you enjoyed this episode and you want to watch some episodes, not this one, unfortunately, but many, many others, you can actually watch us on Netflix. I feel like a lot of my regular listeners know this by now.

But yes, we are all of our episodes, our video episodes are available on Netflix for you to watch. So you can go and see our cool backdrop, our cool, a little studio. It's a very, very cute. What else do I have to say? Substack. I don't, oh, my God, I always forget. There's always so many things on the list now of like, who do I need to thank? Thanks to you guys for listening.

There you go. You guys never get to thank you. You can have a thank you today. Thank you for listening. Thank you for making it to the end if you made it this far. Leave a little brain emoji down below if you are listening on Spotify. But yeah, until next time, be safe, be kind, be gentle with yourself. We will talk very, very soon.

There was no anything inside those eyes. They turned black. It scared the hell out of me. Evil, wake up. I'm the one that saw the murder take place by Creveth and DePippo. Anthony DePippo showed no signs of remorse, appearing unfazed after being sentenced to the maximum. I said I'm not guilty.

I'll take it to the grief. Listen to the devil's quarry in the Bone Valley Feed on the IHeart Radio app. Apple Podcasts, or wherever you get your podcasts. Joy is a set. and it's also elusive, but now there's a new and exciting way to start your journey toward a more joyful existence, Joy 101. It's a new podcast hosted by me, Hoda Kotby. If you're craving inspiration to maximize your joy, tune into these candid, uplifting, and moving on-air chats. Open your free iHeart radio app. Search Joy 101 and listen now. Joy 101 with Hoda Kotby is presented by CVS.

Everyone sees me as a football player But before anything else, I'm human Every single day I'm still learning How to live with problems, mistakes, relationships, emotions ever since I was born. This isn't a normal podcast. Everything here is spontaneous, real and genuine. Just honest conversations about what it means to be alive.

I'm Javier Tchariot Hernandez And listen to Learning to Be Human on IHard Radio, Apple Podcasts, or whatever you get your podcast. June is Black Music Month And on the Drink Chams podcast, we're speaking with the hottest names in the culture, like Sway Lee. Do you realize how legendary you are?

I appreciate that. I'd be seeing it, but I'm like, man, I still got, like, so much more to do. Like, Prince, he dropped, like, 30 albums. We dropped, like, five right now. Like, that's the rate we gotta be going. Yeah, that's a good attitude. No matter the era, Drink Chams brings you the biggest names and the most unfiltered conversations.

Listen to Drink Chams from the Black Effect Podcast Network on the IHeart Radio app, Apple Podcast, or wherever you get your podcast. Here's something that should not be as complicated as it is, getting a racist statue removed. And here's something that should be a whole lot easier than it is, getting a new one put up in its place. I'm Akela Hughes, and Rebel Spirit Season 2 is about both of those things. As I was watching these statues come down, I was thinking about what it meant that I grew up in a majority black city, in which there were more homages to enslavers than there were to enslave people.

Listen to Rebel Spirit Season 2 on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. This is an IHeart podcast Guaranteed human