Do you find yourself being Confused by Your Teenager’s Behaviour? Many of us find ourselves tearing out our hair over our  teen’s moods and behaviours and wonder what happened to the adorable, sweet-natured child we had; as what at times appears to be an alien emerges.  We may blame ourselves, our partner and may even feel guilty, inept or ashamed.

The purpose of this article is to explain the difference between a child, adolescent and adult brain. To de-mystify why our teen behaves the way they do and how we can support them on the journey to being a fully functional adult.

First of all I will explain the structure of the human brain. The brain sits on the brainstem, which connects to the spinal cord. It is divided into four lobes – Different functions tend to be associated with particular areas of the lobes.

  • Frontal (top front) – concerned with executive function, reasoning, problem solving, working memory, judgement, insight and impulse control. Plus the execution of fine voluntary movement.
  • Parietal (top back) – is divided into two functional regions. One involves sensation and perception and the other is concerned with integrating sensory input, primarily with the visual system. The first function integrates sensory information to form a single perception (cognition).
  • Temporal (sides) –discrimination of sounds and includes areas involved in the regulation of emotions and sexuality, language
  • Occipital (back) – house the visual cortex. The cerebellum in the rear of the brain regulates motor patterning and co-ordination


In addition, there is a complex system of nerves and networks in the brain, involving several areas near the edge of the cortex concerned with instinct and mood. This is referred to as the limbic system and can be thought of as a kind of crossroads of the brain, where emotions and experiences are integrated.

These structures control the visceral (relating to deep inward feelings) and physical expressions of emotion – quickened heartbeat and respiration, trembling, sweating and alterations in facial expressions – the expression of appetite and other primary drives; hunger, thirst, mating, defence, attack and flight.

The hippocampus is a small organ located within the brain’s temporal lobe and forms an important part of the limbic system. It is associated mainly with memory, in particular long-term memory. The organ also plays an important role in spatial navigation. In the adolescent brain it is relatively “supercharged” compared with an adult’s.

Amygdala – There are two amygdalae per person normally, with one amygdala on each side of the brain. It is responsible for emotions, survival instincts, and memory and also plays a role in sexual activity and libido, or sex drive.  The amygdala is responsible for the perception of emotions such as anger, fear, and sadness, as well as the controlling of aggression. The amygdala helps to store memories of events and emotions so that an individual may be able to recognize similar events in the future.

The Hypothalamus is a section of the brain responsible for the production of many of the body’s essential hormones, chemical substances that help control different cells and organs.  The hypothalamus’ primary function is homeostasis, which is to maintain the body’s status quo system-wide.


Grey matter houses neurons – these are the cells responsible for thought, perception, motion and control of bodily functions.

These cells also need to connect to one another, as well as to the spinal cord for the brain to control our bodies, behaviour, thoughts and emotions. Most of these connections to other neurons are through the white matter in the brain.

In the past it was assumed that whatever our IQ or apparent talents, a math or science type versus a language arts type, at puberty it stays that way for the rest of our life. Now we understand that this is all wrong.  The teen brain in particular has the ability to harness exceptional strengths that fade as we enter into adulthood.

The functioning, wiring and capacity of the brain are all different in adolescents. The teenage brain is a wondrous organ, capable of titanic stimulation and stunning feats of learning and on the other hand has dangers, including impulsivity, risk-taking, mood swings, lack of insight and poor judgement.

Children’s brains continue to be moulded by their environment, physiologically, well past their mid-twenties. Scientists are continually uncovering ways in which the adolescent brain works and responds to the world differently from the brain of either a child or an adult.

The brain of an adolescent has an overabundance of grey matter (the neurons that form the basic building blocks of the brain) and an undersupply of white matter (the connective wiring that helps information flow efficiently from one part of the brain to the other). It is almost like a brand-new Ferrari;  It’s primed and pumped, but it hasn’t been road tested yet.  It’s all revved up but doesn’t quite know where to go.  The teenager looks like an adult and yet neurologically their brain is not ready for the adult world.

The brain is built by nature from the ground up – from cellar to attic, from back to front. The brain also wires itself starting in the back with the structures that mediate our interaction with the environment and regulate our sensory processes  (The Limbic System ).

As the brain matures from back to front in the teen years the frontal lobes are the least mature and the last connected compared with the other lobes.

The frontal lobes make up more than 40 percent of the human brain’s total volume – they are the seat of our ability to generate insight, judgement, abstraction and planning. They are the source of self-awareness and our ability to assess dangers and risk so we use this area of the brain to choose a course of action wisely.

A chimpanzee’s frontal lobes come closest to the human’s in terms of size but still make up only around 17 percent of it’s total brain volume.   The human’s competitive edge is our ingenuity, brains over brawn.  This edge happens to take the longest time to develop as the connectivity to and from the frontal lobes is the most complex and is the last to fully mature.

New forms of brain scans, called magnetic resonance imaging (MRI) not only gives us accurate pictures of the brain inside the skull but also shows us connections between different regions . A new kind of MRI called the function MRI (fMRI) shows us what brain areas turn one another on.  The National Institutes of Health (USA) conducted a major study to examine how brain regions activate one another over the first twenty-one years of life.

What they found was:-

  • The connectivity of the brain slowly moves from the back of the brain to the front. The very last places to “connect” are the frontal lobes.
  • The teen brain is only about 80 percent of the way to maturity. This 20% gap where the wiring is thinnest, is crucial and goes a long way toward explaining why teenagers behave in such puzzling ways – their mood swings, irritability, impulsiveness and explosiveness; Their inability to focus, to follow through and to connect with adults; their temptations to use drugs and alcohol and to engage in other risky behaviour.

The process of brain maturity is not completed by the end of the teen years and as a result the college years are still a vulnerable period.

We have all heard tragic stories of deaths due to recklessness – swimming whilst intoxicated, driving recklessly, etc. etc. Police, teachers, parents ask kids to think twice about potential dangers before taking any risks that could turn deadly.

How parents deal with these tragic stories and talk about them with their own kids is critical.  It shouldn’t be “Oh, I’m so glad that wasn’t my child” Or “my teenager would never have done that” because you just don’t know.

Instead parents have to be proactive. Stuff the teenager’s  mind with real stories, real consequences and then you have to do it again – over dinner, after soccer practice, before music lessons and even when they complain they’ve heard it all before. You have to remind them!

Now that you have an understanding how the teenage brain is not yet sufficiently mature to make logical decisions, to have insight, solve problems, make judgements  and exercise impulse control, Watch this space! In future articles I will discuss how this immaturity affects various contexts  of their lives – relationships, including peer pressure, sex, studying and planning, stress and how easy it is for them to adopt addictive behaviours.

Source “The Teenage Brain: A Neuroscientist’s survival guide to raising adolescents” by Frances E. Jensen

Resources: Parenting Teens Online and Talking Teenage