http://www.psychologytoday.com/blog/.../effects-porn-
adolescent-boys
Between the ages of 12 and 20, the human brain undergoes a period of great 
neuroplasticity. The brain is in a malleable phase during which billions of new synaptic
connections are made. This leaves us vulnerable to the influence of our surroundings 
and leads our brains to be "wired" around the experiences and information that we 
receive during that time period.
When an adolescent boy compulsively views pornography, his brain chemistry can 
become shaped around the attitudes and situations that he is watching. Sadly, 
pornography paints an unrealistic picture of sexuality and relationships that can create 
an expectation for real-life experiences that will never be fulfilled.