Measuring risk

"The brakes come online somewhat later than the accelerator of the brain," said Johnson, referring to the development of the prefrontal cortex and the limbic system respectively.
At the same time, "teens need higher doses of risk to feel the same amount of rush adults do," Johnson said.
Taken together, these changes may make teens vulnerable to engaging in risky behaviors, such as trying drugs, getting into fights or jumping into unsafe water. By late adolescence, say 17 years old and after, the part of the brain responsible for impulse control and long-term perspective taking is thought to help them reign in some of the behavior they were tempted by in middle adolescence, according to McNeely and Blanchard. [Why Teens Do Stupid Things.]
What is a parent to do in the meantime? "Continue to parent your child." Johnson said. Like all children, "teens have specific developmental vulnerabilities and they need parents to limit their behavior," she said.
Research on the different rates of brain function development during adolescence was published in the journal Developmental Review in 2008.