In the adolescent brain emotions prevail over self-control
The young more often take risky decisions than adults. PhD candidate Linda van Leijenhorst has discovered why: the brains of the young are extra sensitive to rewards, while the brain areas that are supposed to keep a person´s behaviour under control have not yet fully matured
The young more often take risky decisions than adults. PhD candidate Linda van Leijenhorst has discovered why: the brains of the young are extra sensitive for rewards, while the brain areas that are supposed to keep a person´s behaviour under control have not yet fully matured.
Risk seekers
Riding a moped without a helmet. Experimenting with drink and drugs. Teenagers cause both their parents and researchers to face the question: Why? Why do teenagers dive headlong into risky situations that most adults would avoid? This is the very question psychologist Linda van Leijenhorst is trying to find an answer to in the Leiden Brain and Development Lab at the Department of Developmental and Educational Psychology. The PhD candidate asked test subjects from different age groups to perform simple gambling tasks, while at the same time she charted their brain activities with an fMRI scanner.
Linda van Leijenhorst: ‘Brain scan techniques have made it possible to study changes in development, even when they are not perceptible in a person´s behaviour.’
Imbalance in development
The brains of teenagers turn out to work differently from those of adults when it comes to making decisions. ‘Teenagers are a good deal more sensitive to the prospect of possibly being rewarded,’ Van Leijenhorst explains. In her experiments, the test subjects could win small amounts of money with their decisions. The fMRI results showed that the activities of certain brain areas is at its highest around the ages of 14 to 15. ‘The reward areas in the brain develop earlier than the brain areas that are supposed to control the behavioural impulses. That is why teenagers are more prone to take risks: they are in search of kicks and are not able to regulate their own behaviour properly.’
Image – Brain areas that are sensitive for rewards (called ‘emotion areas’ here) are the most active during mid-adolescence. Brain areas that control the emotions are not yet fully developed then. This explains why teenagers are eager to take risks: emotions prevail over self-control.
Against better judgement
Even though teenagers take many risks, they often understand quite well what the consequences could be. A experiment conducted by Van Leijenhorst showed that 8-year-olds are already capable of weighing their chances and anticipating rewards at an adult level. This makes it unlikely that teenagers are taking risks because they are ignorant of the possible consequences. ‘Most teenagers really do understand that is not a good idea to chat with friends on MSN when they ought to be studying for a test. But they do it anyway. Chatting with friends offers a social reward they simply find difficult to resist.’
Brain scanner
Van Leijenhorst´s doctoral research is the latest addition to a series of pioneering studies that has brought the Brain and Development Lab a good deal of publicity in recent years. The newest brain scanners make things possible that researchers previously only dreamt of, Van Leijenhorst says. ‘For the first time in history there is a technology available that we can use to produce images of the brain in operation. The fMRI scan has made it possible to study changes in development, even when they are not perceptible in a person´s behaviour. In some cases, adolescents and adults display identical behaviour, while it turns out that there are differences in the brain processes that are at the basis of this behaviour.’
Limitations
And yet, even this technology has its limitations. Explaining differences in individual behaviour in particular is still a ´bridge too far´ at this stage. Van Leijenhorst: ‘Our conclusions are based on group averages. The activity in a certain brain area of an individual can deviate from the average in a group. That is why we have not yet succeeded in predicting which adolescent has a heightened chance of displaying risk behavior, based on his or her brain activity.’
Image: The flexibility of the adolescent brain does offer teenagers many possibilities to discover themselves and the world.
Individual differences
Van Leijenhorst believes this presents a major challenge: to explain individual differences between adolescents. This is because these individual differences in both behaviour and brain activity are large among adolescents in particular. Research into these differences might have social implications as well. Van Leijenhorst gives as an example the Dutch school system: ‘The present teaching methods are mostly aimed at the average teenager. But one student might be more capable of working independently than another.’
Discover the world
To encourage this next stage in her research, the Netherlands Organisation for Scientific Research (NWO) awarded Van Leijenhorst a Rubicon grant in December 2009. The psychologist has been a guest lecturer at the University of California in Los Angeles for 18 months. Adolescence as subject of research has not yet lost any of its appeal for her. Not only because many youths display – in various degrees – risky behaviour, but also because Van Leijenhorst believes it is a period with unlimited possibilities. ‘The very fact that adolescents are less careful and their brains are still fully in development, makes adolescence a unique opportunity to discover the world and gain lots of new knowledge.’
Van Leijenhorst, L., Why teens take risks: A neurocognitive analysis of developmental changes and individual differences in decision-making under risk
Defence of the doctoral dissertation: 19 January
Faculty: Social and Behavioural Sciences
PhD supervisors: Professor E.A. Crone, Professor P.M. Westenberg
(19 January 2010/Tristan Lavender)