To teens, benefits are more persuasive than risks

Adolescents can give their parents and teachers a scare. Many kids engage in street fights, binge on alcohol, take risks while driving and party late into the night with strangers. Teenagers simply tend to take more risks than adults — and brain scientists want to know why. A new study offers some clues as to why teens seem so prone to taking costly chances or making unwise decisions.

It found that for these young people, rewards tend to be far more influential than consequences. For instance, when considering whether, say, to cut class to see a movie, most will be more persuaded by the perceived fun than by any negative consequences (such as missing an important lesson). “This could result in risky behavior, such as driving cars unsafely,” says Stefano Palminteri. He studies how the brain learns and makes decisions at  École Normale Supérieure in Paris, France.

His team’s new study was published in PLOS Computational Biology on June 20.

The researchers recruited two groups of participants to play a computer game. One consisted of people between the ages 18 and 32. The other included adolescents 12 to 17 years old. Each person was presented again and again with different pairs of symbols on a computer screen. Each time, a recruit was asked to choose one.

Some symbols led to a reward (winning a point). Others led to a punishment (losing a point). Sometimes, players got zero points for choosing a symbol. The players were told to get as many points as possible. A high score could fetch them a monetary reward equal to about to $13.

Before starting the game, players had no idea which symbols would give them points. They had to find that out through trial and error. Along the way, they sometimes got a hint: The game would sometimes tell them what the other symbol would have added to — or subtracted from — their score.

The researchers also built three computer programs that could play the same game. Since these programs were “smart,” they could learn from their mistakes, just as the human players had.

The team then compared the scores of the computer programs to those of the human players. Scores of the younger players matched up best with a computer program that only learned from rewards. That is, every time it gained a point, the program would remember that symbol and choose it more often. However, it basically ignored the repercussions of its bad moves — times when it chose a symbol that ended up robbing it of a point.

Adults responded differently. Their learning resembled that of a more complex computer program. In short, they took a more cautious approach. They not only learned to recognize symbols that won them points but also kept good track of symbols that lost them points. They also were more likely to keep track of any hints offered up during their play about symbols they hadn’t chosen. 

“Our data suggests that when rewards and punishments are equal in value … adolescents are more likely to take the rewarding information into account in future choices,” says coauthor Emma Kilford. She works at University College London, in England. There she studies the development of various types of brain processes.

Nathaniel Daw works at Princeton University in New Jersey. As a computational neuroscientist, he uses math and computer programs to probe how the brain works. Scientists are now beginning to understand a lot about learning and decision-making in adolescents and college students. In this context, he says, the new study is like a “nice piece of the puzzle.”

Could schools learn something from such studies? Recent research has provided some clues about the erratic behavior of teens and tweens. One possibility is that their brains are not fully developed.

But Daw cautions that we “aren’t quite there yet.” However, he notes, studies like this one are laying the basis for programs that might one day aid teens and others who have trouble with self-control.