I remember being extremely influenced by my friends. At the time, I didn't think of it as the old "giving into peer pressure," but that's totally what it was. Whatever my friends wanted me to do, I was doing it. I remember acting on impulsions all the time, but then feeling guilty afterwords--it was like I didn't have any forethought (and after reading the article this week, maybe I REALLY didn't have the ability to think about the consequences of my actions).
I had a friend my senior year of high school who had gotten a felony and wouldn't tell any of us how it happened--he was very ashamed. One day he finally told me it was because he had slashed all the tires of every car in an entire parking lot. When I asked "why," he said "I have no idea." I think this really sums up the way teenage brains work...