Adults are good at putting maximum mental effort into the things that matter most. But teenagers may know full well how important final exams are - however that won't stop some putting in minimal effort. This may be because their brains aren't developed enough to properly assess how high the stakes are, and adapt their behaviour accordingly.

Adults are generally pretty good at being able to tell when a situation is worthy of extra time or concentration. Research has found that, when potential rewards or losses are higher, for example, adults will perform better on tasks. But this doesn't seem to be the case for adolescents.


Attempts to improve student grades with money have had mixed success. 

Catherine Insel, at Harvard University, and her team asked adolescents between the ages of 13 and 20 to play a game while lying in an MRI brain scanner. In some rounds of the game, participants could earn 20 cents for a correct response, while an incorrect one would cost them 10 cents. But in rounds with higher stakes, correct responses were worth a dollar, and wrong answers lost the participants 50 cents.


The team found that while the older volunteers performed better in the high stakes rounds, the younger ones didn't - their performance didn't change in line with whether the stakes were low or high. And the older the volunteers were, the more improved their performance was. "Interestingly, the ability to adjust performance according to the stakes at play emerged gradually across adolescence. These findings demonstrate that brain connectivity continues to develop across adolescence, " says Insel. 


When the team looked at the brain activity of the volunteers, they found that their ability to improve their performance was linked to how developed their brains were. A region called the corticostriatal network seemed to be particularly important. This area is known to connect areas involved in reward to those that control behaviour, and continue to develop until we are at least 25 years old.