from what I have seen, many dogs were fearful of certain things when they were tender puppies.. but as they grew up, they became beasts and wanted to kill that by which they were afraid when they were puppies.. there is another category of dogs.. they r friendly with everybody.. but they get aggressive and attack only when they/their family are/is attacked. so, I think this explains everything. if they react to a threat, why do they react? obviously because they feel threatened. if they r strong, the fear dissolves in their will to act, or if they are weak, their resolve to protect their turf runs helter skelter and a fear or being eliminated dictates their mind and body. thats what my opinion is..