Due to the increase in brain matter, the teen brain becomes more interconnected and gains processing power, Johnson said.
Adolescents start to have the computational and decision-making skills of an adult –if given time and access to information, she said.
But in the heat of the moment, their decision-making can be overly influenced by emotions, because their brains rely more on the limbic system (the emotional seat of the brain) than the more rational prefrontal cortex, explained Feinstein.
"This duality of adolescent competence can be very confusing for parents," Johnson said, meaning that sometimes teens do things, like punch a wall or drive too fast, when, if asked, they clearly know better.

Scientists used to think only infants have an overabundance of neuronal connections, which are "pruned" into a more efficient arrangement over the first three years of life.
But brain imaging studies, such as one published in 1999 in Nature Neuroscience, have discovered that a second burst of neuronal sprouting happens right before puberty, peaking at about age 11 for girls and 12 for boys.
The adolescent's experiences – from reading vampire novels to learning to drive – shape this new grey matter, mostly following a "use it or lose it" strategy, Johnson said. The structural reorganization is thought to continue until the age of 25, and smaller changes continue throughout life.