Xavier, 16, invites a group of his high school friends to swim in a neighbor's pool late at night while that neighbor is away. They climb the fence and jump in, playing wildly and loudly in the water. Just a few minutes later, the police arrive. How does adolescent brain development help explain Xavier's poor decision making?

His prefrontal cortex is underdeveloped.    

Explanation:

The "prefrontal cortex" is also written as "PFC" and is defined as the "cerebral cortex" that covers the front part of a person's frontal lobe of the brain. The prefrontal cortex is being implemented or is significant in planning or developing personality expression, moderating social behavior, complex cognitive behavior, and decision-making process, etc.

A person's prefrontal cortex is being fully-developed or matured at the age of twenty-five years and therefore an adolescent has underdeveloped prefrontal cortex.

As per the question, Xavier's poor decision making is due to the fact that his prefrontal cortex is underdeveloped.