According to brain researchers, a young man's prefrontal cortex usually doesn't fully develop until he's about 25 years old.

This means that this section of the brain's frontal lobe—which governs decision-making and planning complex behaviour—isn't always up to the task of assessing risk in the teenage years and early 20s.

This helps explain why so many young men were acting like hooligans during the Stanley Cup riot in Vancouver in 2011.

It also offers insights into why teenagers and very young adults engage in dangerous activities like rooftopping, which involves sliding along the roof of skyscrapers.

Today, Vancouver police issued a warning after one of these incidents occurred in the downtown core.

Citytv's Tom Walsh tells the tale in the video below.