Teenagers are more selfish than adults because
they use a different part of their brain to make
decisions compared to adults, new research suggests.
Previous work has shown that when children reach
puberty, there is an increase in connections between
nerves in the brain. This occurs particularly
in the area involved in decision-making and awareness
of other people’s feelings, called the "mentalising
network".
Now Sarah-Jayne Blakemore, a cognitive neuroscientist
from University College London, UK, has used functional
magnetic resonance imaging (fMRI) to scan the
brains of 19 adolescents (aged 11 to 17) and 11
adults (aged 21 to 37) whilst they were asked
questions relating to decision-making. Questions
such as: “You’re going to the cinema, where do
you look for film times?”
Blakemore found that teenagers rely on the rear
part of the mentalising network to make their
decisions, an area of the brain called the superior
temporal sulcus. In contrast, adults use the front
part, called the prefrontal cortex.
The superior temporal sulcus is involved in processing
very basic behavioural actions, whereas the prefrontal
cortex is involved in more complex functions such
as processing how decisions affect others. So
the research implies that "teenagers are less
able to understand the consequences of their actions",
says Blakemore.
Taken care of
In a separate experiment, Blakemore asked 112
participants (aged from 8 to 37) to make decisions
about other people’s welfare and timed how long
it took them to respond. The questions included:
"How would your friend feel if she wasn’t invited
to your party?"
She found that the response time got shorter
as the participants got older, suggesting that
the older people found it easier to put themselves
in other people's shoes.
Blakemore suggests that both findings might be
explained by an evolutionary mechanism in which
the development of the brains of adolescents takes
precedence over its performance. “You don’t need
to be on a par with other people because you are
looked after until reproductive age. Only then
do you need to start to take into account other
people’s perspectives.”
Work in progress
The work has implications for the types of responsibility
given to adolescents, Blakemore says: “Teenager’s
brains are a work in progress and profoundly different
from adults. If you’re making decisions about
how to treat teenagers in terms of the law, you
need to take this new research into account.”
Sam Lewis, a specialist in youth crime and justice,
from the University of Leeds, says there has in
fact been a shift away from welfare-focused approaches
to youth punishment in the UK: “Today, responses
to youth crime tend to emphasise offender responsibility,
accountability and punishment. It seems likely
that the concerns of many, including those of
Dr Blakemore, may be lost in the tide of punitive
policies being pursued by the government.”
The research was presented at the British Association
for the Advancement of Science Festival in Norwich,
UK.
