Proactive aggression is aggressive activity that occurs with little or no overt provocation. An example of this would be a dog that attacks someone for simply walking past their owner's property. This type of aggression can be summed up as "I'm going to get you before you get me!" and is a fear or anger reaction to an assumed threat. This is the opposite of reactive aggression (hyperlink?) which occurs when there is a reaction to an actual and overt threat.