The Secret Life of the Teenage Brain
By Sarah-Jayne Blakemore
Published by Doubleday
A snapshot of last Saturday in our household: the 13-year-old has lost £10 and, having tipped everything out of his cupboard, wails: “It’s been stolen!” The 17-year-old, who’d been arguing that studying hard for A-levels is a capitalist construct, wanders by and quips: “Money doesn’t make you happy.” The middle teen, trying to be good, gathers four dirty mugs from her room and dumps them in the sink — the dishwasher remains beyond her comprehension.
So what makes the adolescent brain so frustratingly truculent? And what drives a teenager’s excessive risk-taking and need for intense friendships?
Endeavouring to answer these questions is Sarah-Jayne Blakemore, 43, professor in cognitive neuroscience at University College London, whose father Colin is one of Britain’s most eminent neurobiologists. Her first solo book is packed with brain studies going back more than 100 years and is replete with the technical minutiae of how our 86bn neurones work. Her premise is this: while visual and auditory synapses reach adult levels at 12, the brain is far from fully formed by then, especially the prefrontal cortex, a small region in the forehead responsible for, among other things, decision making, spatial navigation, memory and moderating social behaviour. (When she started her research in 2001, the received wisdom was that the human brain was mature by late childhood.)
“On the basis of the last 20 years of research...adolescent brains are different from children’s and adults’ brains — they are in the process of development,” she concludes. You might not have needed a degree from Oxford to have guessed that.
In her search for the “secret life” of the teenage brain, many of Blakemore’s studies also seem to fall into the category of the “bleeding obvious”. One study looked at whether teens are negatively affected by being socially excluded, using a computer catch game called Cyberball. It concluded that “adolescents are hypersensitive to social exclusion”.
Did this fear of exclusion influence risk-taking? Another video game, The Stoplight Task, confirmed that yes, teens were three times more likely to risk jumping an amber light if their friends were with them. And guess what? Smoking weed at least four times a week at 18 damages your IQ. And if you want to persuade a teen to do something, bribing them with money works better than threatening punishment.
Blakemore’s book might be thin on revelations to anyone living with teenagers, but the biological details are often fascinating. Who knew that the grey matter in our prefrontal cortex “dramatically declines between late childhood and early adulthood, reducing by about 17%”? Which doesn’t mean that neurones are dying, but that synapses not used are simply being “pruned”. That sounds rather brutal, but Blakemore says this pruning just “reflects processes that help define and refine a maturing brain” — such as exposure (or not) to culture, education, home and social life, hobbies, nutrition and exercise. The (obvious) conclusion is that investing energy in a wide range of interesting experiences helps the brain grow.
What many parents also want to know, however, is how damaging social media and phone addiction are to a developing brain. There is little to report on this, a fact that frustrates Blakemore as much as it will her readers.
“We urgently need systematic and controlled studies looking at this important question,” she writes, having earlier highlighted the unfeasible cost of neurological studies, with just one MRI scan costing £500 per hour.
Blakemore is obviously a passionate cheerleader of the teenage brain, and by the end of her book you feel more compelled to nurture their neurones rather than lambast them, in the hope that not too many get pruned.
So, back to that lost £10. Had the 13-year- old checked all his pockets? “I put it in my backpack!” My aged brain thinks not, and I immediately find it in his jacket.
The next time your teen does the same, put it down to their prefrontal cortex spatial memory. It’s a work in progress.