The teenage brain

It's true, teens can't be punished like adults

Teens tend to take more risks because their brains are not fully developed yet

In the past decade, advances in neuroscience have given new insights into old problems, ranging from drug addiction and post-traumatic stress disorder to adolescent shenanigans.

For example, if the new neuroscience shows that a drug addict's brain is physically dissimilar to a non-addict's brain in ways that make the former more prone to addiction, then we must ask if his infractions of the law ought to be treated less punitively.

It is with such considerations in mind that The Straits Times is publishing a six-part series starting today, with a focus on what the new neuroscience says that is causing experts to revise how they approach these issues. This week, we focus on the teenage brain. Should teens be treated like mini-adults, deserving of society's harshest punishment, when they break the law? New neuroscience findings suggest not.


PHOTO: ISTOCKPHOTO 

For most of the 20th century, experts had fervently held, with little empirical proof, the first three years of life to be the most important for brain development. But from the late 1990s, the new neuroscience began to show that the brain, even in older adolescents, had yet to attain the kind of full maturity seen in adults.

Brain imaging has now established that the brain keeps maturing through adolescence. Not only is the brain's development not done by adolescence, but also it isn't even done until the early 20s.

If the teenage brain is indeed not fully developed, then the teenager cannot be held to be as culpable as an adult. By contrast, in adulthood, when the brain is fully developed, the scofflaw ought to be held fully responsible for his actions.

Back in 1623, Shakespeare had an insight into the tumultuous teen when he wrote in The Winter's Tale: "I would there were no age between ten and three-and-twenty, or that youth would sleep out the rest; for there is nothing in the between but getting wenches with child, wronging the ancientry, stealing, fighting."

But what the Bard couldn't have known then is that a teenager cannot manage his own behaviour in a way the adult can because his brain is not yet fully developed and mature in a biological sense. There is still a lot of child in the teenager. Thus the law ought not to treat teens as if they were adults.

This flies against conventional wisdom of much of the 20th century, whose experts held that the first years of life were the most critical for cognitive development, and that it was too late to make a difference to a person's cognitive development by adolescence.

That dogma came from French psychologist Jean Piaget (1896-1980) who even argued that "children have adult-like reasoning by age 15". It became an article of faith that teens have cognitive abilities like those of adults. This view has now been discredited by empirical neuroscience studies using functional magnetic resonance imaging.

Hitherto, there was no empirical research into the teen brain or teen cognitive development since the notion that things were set in stone in early childhood was entrenched.

So through the 20th century, the courts and policymakers as well as public opinion continued to abide by the ideas about adolescents fostered by Piaget and his followers. Policymakers often rely on common-sense beliefs which are frequently based on and circulated in mass media reports. So it did not seem inappropriate to pass laws that treated teens as mini-adults.

However, 21st-century neuroscience evidence suggests this was all wrong because, in adolescence, the brain changes in a few specific ways that make the teen brain distinct from the brains of the child and the adult.

First, teen brain cells begin to use more dopamine, a chemical related to pleasurable experiences. This is why teens take more risks, even when they have an adult-level cognitive understanding of potential danger, because they value rewards more than adults do when the anticipated act is potentially pleasurable - take sex, fast cars or illicit drugs, for example. Or perhaps, as in the case of the teenager Amos Yee, making and uploading offensive videos.

Research also shows this is true especially when teens are in the company of their peers. This is clear to see today on social media.

Second, the connections between the brain regions for processing emotions and those for self-control begin to increase. This means strong feelings are modulated better as the teen grows. But while still developing, that control can be spotty.

Third, the prefrontal cortex behind the forehead is where the brain circuits for higher cognitive functions like weighing risks and long-term planning are located. In teenagers, white matter in that region increases, which becomes more efficient functionally. Critically, this increase in white matter continues well into early adulthood, which means it is not quite done yet in late adolescence.

It is in middle adolescence that a teen brain's response to rewards peaks. However, its systems for self-regulation are still growing. So the pedal is to the floor but the brakes aren't working too well yet.

That is why it is around the age of 17 that teens first try alcohol and marijuana, attempt suicide or drown by accident. Or just get into trouble with the law.

Here's the rub: The teen brain changes in both structure and function but the timing and rate of such changes are not uniform. So there is no bright line for a specific age at which an adolescent brain becomes an adult one. But it is clear that such maturation is not largely complete in early childhood, as previously held so dogmatically.

It is also clear that in adolescence, intellectual maturity develops faster than social or emotional maturity. So teens who are astute in some areas may remain impetuous and short-sighted in others. They may be able to reason like adults but are inconsistent in doing so.

All this means there is more biological evidence that the law ought to afford more protection to minors since they are neurologically immature in ways that make them take more risks, be more impulsive and less able to control their emotions than adults.

It also suggests that teens deserve special protection in criminal law because their brains are not fully biologically mature.

Because the brain undergoes massive changes between the ages of 12 and 21, we're now told, there are structural and functional immaturities in the adolescent brain which give rise to behavioural immaturities. So minors are not in the same position as adults.

We have long known that teens are more likely than adults to be thrill-seeking and impulsive. Now science is telling us this is because the teen brain is still maturing.

It all suggests that, on biological grounds, there may be a case for not treating teens like adults in law.

•This is the first of a six-part series by Andy Ho on new scientific findings about the brain.

NEXT WEEK: The concussed brain

A version of this article appeared in the print edition of The Straits Times on July 18, 2015, with the headline 'The teenage brain'. Print Edition | Subscribe