Even when we're teenagers, our brains still have a lot of developing to do. New research suggests that teenage brains haven't matured enough to be able to properly recognise and react to the importance of tasks – maybe one excuse to be late with homework.

In a study involving a simple reaction game, older participants proved to be better than younger ones at changing their approach and applying more time and effort as the stakes got higher.

The team from Harvard University in Massachusetts says there was a clear correlation between increasing age and brain development, and an improved ability to adjust as the tasks in the game became more important.

"Interestingly, the ability to adjust performance according to the stakes at play emerged gradually across adolescence," lead researcher Catherine Insel told Jessica Hamzelou at New Scientist.

The researchers asked 88 volunteers aged between 13 and 20 to tackle a game where correct responses earned a small amount of cash, while incorrect ones meant they would lose money from their prize fund.

Changes were made to the rewards and deductions between trials: from a 20 cent reward and 10 cent deduction to a dollar reward and a 50 cent deduction.

The study found that older teens performed better at the high stakes games, whereas the scores of the younger ones didn't change much whether the stakes were low or high.

At the same time, fMRI scans were used to monitor the brain activity of the participants. The scans showed that activity in an area called the corticostriatal network seemed to be playing a significant role.

This is an area of the brain involved with reward and behaviour, and it's not fully developed until we're 25 or so. The researchers found having a more developed corticostriatal network was linked with better performance in the high-stakes games.

"As teens age, they become better at adjusting brain connectivity across motivational contexts, which in turn allows them to do better when working towards a high-value goal," Insel explained to Helen Briggs at the BBC.

So how might this apply in the real world? Studies have shown that adults are very good at adjusting their approach based on the importance of something: so we'll spend much more time preparing for a job interview than for a routine weekly office meeting, for instance.

This new research suggests brain wiring for that kind of prioritising is still under development in teens. It might help explain why younger drivers take more risks perhaps, or why teenagers struggle to study to put in more effort for one final set of exams at the end of the year.

Further studies on a broader range of ages and a wider sample of young people will be needed to understand more about how all this plays into teenage behaviours, but according to Stefano Palminteri from the École Normale Supérieure in France, who wasn't involved in the study, there is a flip side.

"We could look at this the other way around," he told New Scientist. "Adolescents put the same amount of effort into tasks that aren't 'important', and start to prefer hobbies to school."

"It could be a good thing, allowing teenagers to learn complex social skills, for example."

The research has been published in Nature Communications.