What are the general causes of disobedience?

The four main reasons before childhood misbehaviour are:
Attention: The child is trying to find a place within a social group. If they are gettig no attention when behaving in a positive manner they will act out since being someone that acts out is seen a better than not being noticed at all.
Power: The child is trying to establish independance. Typical phrases include "You're not the boss of me" and "You can't make me". They crave a sense of power over their environment.
Revenge: They may have been hurt by the decisions or actions taken by someone and are trying bring what they see as justice through revenge. Trypical thoughts are "They hurt me so I'm going to hurt them".
Withdrawal: The child is overwhelmed by a challenge/difficulty and has simply given up trying.
This information is based on the Neo-Adlerian Model. You could also look up the ABC approach to behaviour modification for further reading. Just Google and it should come up as much literature has been publised on it.