The behavioral/learning theory of criminology holds that people commit crimes because of the way that their environments have influenced them as they have grown up. These environmental factors can be such things as parents, peers, and the media.
According to this type of theory, we learn how to act by experimentation and observation. We do certain things and we see how others react. If our behaviors are reinforced in some way that we like, we will continue to exhibit those behaviors. Similarly, we draw conclusions by watching other people act. If we see them being rewarded for acting in certain ways, we will act in those ways as well.
This leads to the idea that our environments matter. If we act badly and our parents do not properly correct our behavior, we can end up learning that bad behaviors bring good results. Our peers can influence us in the same way. We can also be influenced by what we see in the media. If, for example, we see people engaging in violence on TV shows and not being punished for it, we will draw the conclusion that it is okay to act in that way.
To this way of thinking, then, criminal behavior is caused by faults in our environments. If we are influenced badly by our parents, our peers, the media, and other factors, we will be more likely to commit crimes.