what could be wrong with my dog?

Question
I have a purebread cocker spaniel (black, male.) He is almost two years old. About a year ago, he started growling at people and showing off his teeth and acting like he was ready to attack them. (including my mother and i which he lives with.) As the year went on, it got worse and worse and now he does it mostly everyday. If i try to correct him he does it even more. There are three other dogs in the household but they live outside, seperate from the cocker spaniel. Why is my dog doing this? What could be wrong with him? How can i help the problem? PLEASE HELP!!

Answer
As dogs mature, they take on more and more responsibility.  They see all the people and dogs in the household as a pack with each having their own rank in the pack and a top dog.  Life is much easier if the 2 legged pack members outrank the 4 legged ones.  You can learn to play the role of top dog by reading some books or going to a good obedience class. A good obedience class or book is about you being top dog, not about rewarding standard commands with a treat. Start at http://www.dogsbestfriend.com/  Also see this link, http://www.dogbreedinfo.com./topdogrules.htm

If you are providing proper leadership, then it is your responsibility to protect the pack from strangers.  If you accept them, then he should follow your lead.  

Neutered males are much quicker to accept others' leadership.  It is no cure all, but a big help.  Certainly, an aggressive dog is no candidate for breeding stock.