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KATE BARBER talks with well-known neuroscience educator NATHAN WALLIS about major changes to the brain during adolescence, and asks the question on many parents’ minds.

In his play The Winter’s Tale, Shakespeare refers to the ‘boiled brains’ of youth, writing that ‘I would there were no age between sixteen and three-and-twenty, or that youth would sleep out the rest’. The bard engages with a rather negative yet humorous stereotype about teenagers – one that sounds familiar some 400 years later.

In light of relatively recent discoveries about changes to the brain during adolescence, Nathan strives to debunk certain stereotypes – that ‘teenagers are foolish, lazy, moody and revolting’.

The image of ‘boiled brains’ may not be too far off the mark – the brain is in fact undergoing major restructuring, says Nathan. At some point during adolescence, for approximately three years, the frontal cortex – the rational part of the brain, where decisions are made, goals are set and consequences weighed – is ‘shut for renovations’, he explains. A process of ‘pruning’ takes place, where the brain works out what’s being used and ‘myelinates’ (reinforces) those pathways it wants to keep.

During this time, the limbic system – the emotional, and sexual, brain – fires on all cylinders. In fact, Nathan says that teenagers are ‘biologically primed’ to operate in their limbic system – driven by their feelings – around 90 per cent of the time. If a teenage girl feels fat, for instance, no amount of explaining to her that she is only a size 10, which is healthy and slim, will convince her, says Nathan. Logic will not prevail; her emotional brain is in control.

Conversely, he points out, adults – with fully mature brains – make ‘feeling’ decisions around 10 per cent of the time, and operate in their logical brain most of the time.

On average, says Nathan, the brain is fully developed around 26 years of age. Later than one might expect…. ‘Girls’ brains grow faster’, he adds, ‘so it might be between 18 and 24 for a female. Whereas boys’ brains develop more slowly, so it might be between 22 and 32 before the male brain reaches full maturity.’ Nathan points out that ‘the research offers a yardstick measurement; it does not describe individuals. Ultimately, parents are the experts when it comes to knowing their kids.’

The narrative gets interesting when you factor in a person’s birth order. The first-born child has the advantage of having mum or dad ‘in their face’ more when they are a baby, and tends to spend more time in the ‘dyad relationship’ with the primary parent or carer – because, by the time Baby 2 comes along, mum and dad also have a toddler, he explains. This is awesome for the development of the brain of Baby 1 – and the positive outcomes are long-term. When the first-born is a girl, they are doubly advantaged.

Nathan urges parents not to compare their kids – especially their first-born daughter with their second-born son. ‘His brain will reach maturity, but it may well take longer. For a first-born girl, her brain might reach full maturity at 18. Her younger brother might be 32 when his brain is fully developed.’

So, as to the question on many parents’ minds, there is no short answer to the ‘when’ part – except that it could take longer than you had expected, and hoped.

Opening people’s minds to the incredible, relatively recent discoveries on the development of the brain, charismatic neuroscience presenter and director of X-Factor Education Nathan Wallis provides an informative narrative on the different stages of children’s neurological development, offering valuable advice for parents across New Zealand and overseas.


Advice for parents
  1. Validate your teens’ emotions. Listen by responding to the emotional brain – which dictates their behaviour 90 per cent of the time. Adults are logical and tend to counter teens’ emotional outbursts/behaviour with logic. Listen more, control less.
  2. Seize opportunities to talk to your teen when they want to talk. If you notice that their frontal cortex is online, go with it – even if the timing is inconvenient and the topic they want to discuss doesn’t seem so important to you.

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