Could the brain actually be responsible for teenagers “acting out”?

By Sarai Ballesteros [original research by Qu, Galvan, Fuligni, Lieberman, & Telzer, 2015]


Would you ever go to a highway with your friends in two separate cars and purposely drive towards each other at full speed until one of you swerves out of the way? Neither would I. However, there are teenagers that actually do this for fun. It’s a game widely known as “chicken.” It is risky behaviors, such as these that have intrigued scientists for centuries. At last, scientists are finally finding reasons for these puzzling behaviors.

Yang Qu and colleagues searched for a biological basis for adolescent’s uniquely risky behaviors. In their paper entitled “Longitudinal Changes in Prefrontal Cortex Activation Underlie Declines in Adolescent Risk Taking” (2015), researchers found evidence that points to underdevelopment in specific brain regions in adolescents that play major roles in decision-making.

In this study, there were a total of 21 participants. All underwent testing at two different points in their lives, about one and a half years apart. The average age of the participants during the first round of testing was about 16 years old. At the second point, the average age was about 17 years old. Each participant was tested on different components to track their degrees and frequency of risky behaviors.

The first component of this study was a survey first created in 1991 named the Youth Self-Report. This questionnaire asks participants how often they smoke, drink alcohol, use drugs, and steal. At the end, the report gives the participant a score from 0-30 from least risky to most risky.

The second component was a task named the Balloon Analog Risk Task, or BART. In this task, participants were put in a Functional Magnetic Resonance Imaging machine (fMRI) and presented with a relatively simple task. They were shown a computer screen that had a red balloon. They were given the choice of either pumping the balloon with air or not. By pumping the balloon, they were running the risk of having the balloon explode in hopes of earning $0.25 with each successful pump. At any point, they also had the option to choose the safe option and cash out and keep all of their winnings. However, if the balloon exploded before they cashed out, they lost everything. With each pump, the chances of the balloon exploding increased exponentially, thus increasing the risk. The test measured how many pumps each participant employed before cashing out or popping the balloon.

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By monitoring participants in an fMRI machine while they completed this task, researchers were able to see the affects of risk on the brain. In whole-brain analyses, they were able to see increased activation in the ventrolateral prefrontal cortex (VLPFC) as well as in the medial prefrontal cortex (MPFC). These two particular areas are known to be related to the brain’s cognitive control and reward systems. Over time, the study found that activation in the VLPFC significantly decreased when making risky decisions on the BART.

Overall, this study does not definitely point to immaturity in adolescents’ brains directly leading to risky behaviors. However, this is a good start to what will likely be a long road to understanding the teenage brain.