Most dogs trained by our residential trainers are ‘aggressive’ or ‘reactive’ in some way. The aggression or reactivity can be triggered by a wide variety of things. The most common ones being other dogs or strangers.
Whatever the trigger is for this adverse behaviour, the most common question we are asked is “why is my dog reactive?”
There are a lot of misconceptions about the reasons dogs are or become reactive, lack of socialisation, Covid dog etc.
Whatever behaviour your dog exhibits or displays. Whether it is good or bad, it will be down to one of, or a combination of, the following three reasons;

1. Genetics
This is the most overlooked or ignored reason for reactive/aggressive nature or behaviour. The simple fact is that most reactivity is fear based. Fear does not necessarily mean shaking and hiding under the table or behind an owner. Levels of fear obviously vary from dog to dog. In some cases, it is more anxiety than actual fear. Either way, there are a lot of dogs born with a certain level of anxiety or fear. The world can be an intimidating place for a young dog and is especially so for one who is genetically nervous. A dog that is genetically confident or robust may easily shake off or get over difficult experiences and recover without any impact on his perception of life. However, for a nervous anxious dog, these difficult experiences have long term consequences that shape their learnt behaviour, from which reactivity develops.

2. Learned Behaviour
This covers dogs that have had a bad experience which then shapes their behaviour in what they perceive as challenging situations. This reason for reactivity is the most common reason owners give us for their dog’s reactive behaviour. However, apart from extremely bad experiences, it will be the dogs that are genetically nervous or fearful that develop reactive/aggressive behaviour because of this. As described above, dogs that are confident and robust genetically are more likely to recover from an unpleasant experience without it effecting their long-term behaviour. How dogs respond to any experience in life will be influenced by the person(s) they are with.

3. Owner Relationship
Dogs are like children in a classroom. Their behaviour will fluctuate in accordance to the person(s) responsible for them. This is not to put the blame for reactive/aggressive dogs at the door of the owners. But to highlight the fact that people with reactive dogs try to solve these problems using human thought processes and emotions, which invariably fail. Over the past few decades, mainstream dog training has become centred on bribery rather than a healthy leadership. As most dog reactivity is fear, anxiety based, using food as a bribe or distraction doesn’t work, as the dog’s fear levels are higher than the value of the food.
…continued at Why is my dog reactive aggressive? Part 2