How the Adolescent Brain Works: A Quick Thought Experiment
Let’s try this:
In a lake, there’s a patch of lily pads. Every day, the patch doubles in size. If it takes 48 days for the patch to cover the entire lake, how long will it take to cover half the lake?
Think about the first answer that pops into your mind.
Got it? Now take a moment and really think it through…
Here’s another one:
A bat and a ball cost £1.10 in total. The bat costs £1 more than the ball. How much does the ball cost?
Pause for a second and consider your answer.
These are classic brain teasers that trip up even very clever adults — because they show something important about how we think.
Two Kinds of Thinking
Psychologists talk about two modes of thinking:
- Hot cognition – fast, emotional, instinctive. It’s great in emergencies or when quick decisions are needed. But it’s also prone to error.
- Cold cognition – slower, more rational, and considered. It’s logical, methodical, and less swayed by emotion.
Adolescents tend to rely more on hot cognition, especially in emotionally charged or peer-influenced situations. That’s not a flaw — it’s a normal part of brain development.
What’s Going On in the Teenage Brain?
It turns out the teenage brain is far less developed than we used to believe. Here’s what science tells us:
- The frontal lobe — responsible for decision-making, planning, and impulse control — doesn’t fully mature until the mid-20s.
- The temporal lobe, which helps process language, memory, and emotional regulation, matures around age 18–20.
This means teens may struggle with weighing up consequences, resisting peer pressure, or staying calm in arguments — not because they won’t, but because they can’t always yet. They’re still learning to manage risk and assess long-term outcomes.
Why Does This Matter?
Because risk-taking is part of adolescence — but it can come with consequences. According to the Royal College of Paediatrics & Child Health:
The leading cause of death among 10–19-year-olds in the UK is accidental injury, including road traffic accidents, accidental poisoning, and drowning. For 15–19-year-olds, transport-related incidents remain a major cause of death and injury.
(Source: rcpch.ac.uk)
Young people are especially likely to take risks when they’re trying to impress peers or under social pressure — classic “hot” thinking in action.
So, What Were the Answers?
1. The lily pad puzzle:
If it takes 48 days to cover the whole lake, it takes 47 days to cover half — because the patch doubles on the final day.
Most people instinctively say “24” — that’s fast (but wrong) reasoning at play.
2. The bat and ball puzzle:
The ball costs 5p, and the bat costs £1.05.
Many people rush to say “10p” — again, fast and intuitive, but not accurate.
What’s the Takeaway?
These puzzles show how easy it is to be tricked by your own brain. Helping young people learn about their thinking processes — and recognising when they’re reacting vs. reasoning — can be a powerful tool for emotional regulation, self-awareness, and making better choices.
What I Do with Young People
That’s what much of my work with adolescents is about:
Empowering them to understand how their brain works—so they can take greater ownership of their thoughts, emotions, and behaviour.
And also, helping them understand their body and physiology, so they become whole beings—aware of how body and mind interact, and their role as living organisms in community. See here for the work I have done with Children and Young People.