Nicola Morgan

Author, Speaker, Supporter

A few speaking slots available in 2025

Your question answered: If a teenage brain is MORE developed than a younger one, why do teenagers often struggle MORE to make good decisions?


This is a great question. It’s also one I’m asked often so the answer is relatively easy! I have a horrible cold at the moment so I’m writing the answer rather than recording a video. You really don’t want to see or hear me.

This was the exact question you asked:

“I do have a copy of your book [Blame My Brain] but I’m confused about PFC/myelination & teens/tweens. What I think I understand is that during adolescence, the PFC is developing. Myelination begins which increases efficiency of messaging between parts of the brain. Meanwhile neural pruning is also happening, My confusion is, do even young children have a fully formed PFC? As PFC is linked to higher functioning but little ones aren’t good at that, is the layer as well constructed? It’s also the emotionality of teen reactions which in part is connected to changes in the PFC which is confusing me, why doesn’t this happen in tweens, eg Y6, Y7s are relatively stable compared to slightly older teens. Perhaps I’m over-simplifying things?”

Let me tackle the myelination part of your question first. Myelination is the process whereby the axons (stems or trunks) of neurons become coated with a fatty substance called myelin. This does indeed make the neurons better at passing their messages between each other via dendrites (branches) and synapses (the near-connections between neurons. This myelination happens to any neurons that have built connections, wherever they are in the brain, not just the prefrontal cortex (PFC). And myelination happens continuously as a brain develops, not only in adolescence. Any development of expertise or skill will involve some myelination and some cells are already myelinated by the time a baby is born.

So, in terms of the question “the emotionality of teen reactions….why doesn’t this happen in tweens, eg Y6, Y7s are relatively stable compared to slightly older teens?” myelination is not the point. There’s something else that explains why teenagers can be less good at controlling emotions and making good decisions than 10-12 year olds.

What’s going on?

Yes, you are correct: during adolescence the prefrontal cortex (PFC) is developing – and it’s the last area to finish its development, which will typically not happen until the mid-late twenties. So, yes, younger children have a less well-developed PFC. And yes, the PFC is linked to and responsible for what you call “higher functioning” – including things like reasoning, self-control, looking ahead, making cool decisions based on future consequences, deep understanding, moral values. All the things that humans do to a far higher degree than even the most “intelligent” of other animals.

Here is my explanation for why, despite having a technically more developed PFC than younger children, teenagers might still (though they don’t always) make more mistakes with control, behaviour, risk-taking and poor decision-making, living in the moment and often ignoring the advice of parents and teachers.

  1. Since the stage of adolescence has at its heart separation from adult protection and drive towards independence, adolescents are more likely not to follow adult lead in behaviour or decision-making. They want to do things their own way, in their desire and attempt to behave independently. What you want them to do is not high in their thinking!
  2. At the same time, the separation from adults means that they need to build bonds with peers instead of adults, so they are driven to follow the lead of their peers, because doing what their peers want or respect is a way to build those bonds. Hence, peer pressure. Humans are social creatures: we need connections with other people and we are biologically driven to seek those connections. Making connections with other people often involves conforming to those people’s behaviours and values.
  3. Teenagers are also typically surrounded by many emotional triggers, with challenging events in their lives at home and school raising the emotional levels within them – more stress, responsibility, knowledge of the world, fear and insecurity. When younger children have pressures, they can easily turn to protective adults, but adolescent are moving away from those protective adults. Adolescent minds can be overwhelmed by these things, and they are less able to be reassured by adults, so they can have brain bandwidth over-occupation. Brain bandwidth over-occupation in anyone leads to more errors of judgement. When there’s too much to deal with, we make mistakes, we’re more snappy and less well in control.

All three of those factors are powerful and hard to avoid, for some more than for others. Your typical adolescent is being biologically driven to separate from adult control and to develop their own independent views and mind, while being bombarded by pressures from friends, schoolwork and family. It’s hardly surprising when they sometimes make mistakes!

So, yes, teenagers have more developed PFCs than younger children, but there’s more pressure on that PFC.

Understanding this will help you, as parents and teachers, and also will help your teenagers. When we have an understanding of how our brain and biology affect our behaviours and emotions, two things happen: first, we stop beating ourselves up or thinking there’s something wrong with us. And, second, we can divert our intention towards managing our behaviours and emotions better. We can make better decisions when we know how those decisions are driven. Reading Blame My Brain – The Amazing Teenage Brain Revealed is the answer!

The NEW edition of Blame My Brain is publishing in February. Have you entered the giveaway? All through February, expect blog posts about teenage brains, including what’s different about the new edition and, importantly, top tips for understanding and supporting the teenagers you care about.

Do comment but please remember that this site is for all ages.


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