|Quoting Continental (Reply 1):|
So that's why you can't rent a car at most places until you are 25...
What usually happens is that older teens and very young adults are quite good in "cold" situations. So they'd have no problem with the marshmallow test.
But in "hot" situations that are emotionally charged, older teens and young adult prefrontal cortices tend to get shut off, and so they and sometimes make decisions "in the heat of the moment" that weren't quite thought through.
This is why a 19yo, caught in the middle of a robbery, is more likely to shoot the person who discovers him than a 30yo, who will have a moment of "I can get off on breaking and entering or I can go for life in jail... better just surrender."
It also explains a lot of driving laws, like why teens are often not allowed to drive with other teens in the car. Teens get into silly games like "only pussies use the brake pedal" and with all their friends jeering and cheering, can wind up making some silly decisions that an adult wouldn't.
This is also why soldiers are drafted at 18. They don't tend to think about the death and dying bit as much as older people.
There is now evidence that there is continuing maturation and changes in the brain throughout the lifespan, which makes sense. But it seems as if decision-making capacity settles down around 25 (+/-3-4 years).
's case...well... he doesn't have a prefrontal cortex.