Many factors come into play in shaping the behavior of adolescents. Some are social in nature; others are biological in origin.
As children reach the age of adolescence, they begin to search for an indentity of their own, separate from their family. This process leads to adolescents spending much more time with peers and placing much more importance upon the opinions and actions of peers than when they were younger. Group dynamics often shape the behavior of adolescents.
At the same time, adolescence is a period of rapid physical and hormonal growth and change but not always at the same rate as peers or even within an individual's body. The amygdala, the part of the human brain that controls emotions and social activities, develops before the frontal cortex, the area used in thinking, planning, learning and applying knowledge, and exercising self-control. This may lead to adolescents acting and reacting based on their emotions, which are predisposed to desire peer approval above all else, rather than rational evaluation of behaviors and possible consequences.