What is different about the teenage brain? Brain development happens over time and generally occurs back to front. This means that the frontal lobe, and pre-frontal cortex, which control executive functions, and are critical to decision making, are some of the last areas of the brain to fully develop.
Other parts of the brain, including those involved with thrill-seeking behavior, reward mechanisms, and intense emotion, come online earlier in the process.
Just as a toddler is able to walk before he or she has the judgment to stay away from dangerous situations (such as the top of a flight of stairs), teenagers can also find themselves in precarious situations for which they are not adequately prepared, from a brain development point of view.
This partly explains some of the risk-taking behavior and poor decision making that is often associated with teens.