Well, there are likely about a billion reasons, from history of reinforcement to the rules and boundaries we set. Dogs are living, thinking beings that learn to behave in certain ways to get what they want, just like people.
The genetic makeup (Genotype) often plays a big part in how motivated the dog will be to access what he or she wants.
This is why it is important to choose a breed to suit your needs, style, energy level and personality from a breeder that is producing stable animals.
The next most influencing factor is the dogs socialisation experience. When you allow your dog to play with other dogs for their highest form of reward, it is inevitable that at some point, that you will have a dog that does not want to follow your instructions to leave the park, walk past a dog without playing etc.
This will not do your relationship with your dog any favours.
The video below shows a beautiful Spaniel girl that just LOVES other dogs. This means that as soon as she see’s one, she does everything she can to get to that dog. She would not listen and would approach any dog, which can be very dangerous if their other dog is aggressive.
Effective Socialisation may include playing with other dogs sometimes, but many more times it should include being calm around other dogs, walking past other dogs and engaging with the owner around other dogs.
It would also mean monitoring your dogs value for other dogs and adjusting interaction experiences accordingly.
More can be read on Effective Socialisation here.
The next and equally important element of owning a dog is setting rules and boundaries and teaching your dog “how to” behave in given circumstances.
The young man on the left used to rough play with the older man on the right. This was dangerous for the little guy.

Boundaries
When a person becomes upset with another person as that person has crossed a boundary, it is usually not a boundary that they have previously outlined, therefore it is only mentioned once it has been broken.
Now, when this is applied to raising a dog, a dog displays a behaviour and somehow finds that behaviour rewarding, or reinforcing is actually the more accurate terminology.
Reinforcement on a behaviour accumulates over every repetition and depending on the circumstances the behaviour will become more frequent and perhaps more intense.
An example may be a dog that resource guards a bone for example. The dog has eaten bones previously, and of course found loads of positive reinforcement in doing so.
He likes them a lot.
One day he is enjoying his bone, and you walk in his direction. As you get close, he begins to think that you might take his bone (-P) and he growls at you.
You stop, change direction, back away and the stress of potentially losing the bone goes away (-R)
This happens now and again, and you will notice that perhaps the dog does not look stressed now but may be more assertive and aggressive around the bone.
This has you concerned, and you think this needs to stop, so instead of avoiding your dog with a bone, you now charge over and say no. This adds more stress because the reinforcement the dog has been getting by growling, negative reinforcement, is not occurring.
In an attempt to regain that reinforcement, the dog has come to expect in the past, an extinction burst occurs and the dog bites you. You inevitably move away, and the dog regains the ability to protect that bone, but by biting now rather than just growling.

You have effectively made the problem worse by A: allowing it to exist in your relationship and gain reinforcement and B: starting to intervene with a program you cannot carry out.
I will not start with this dog by doing anything with the dog’s food, but instead start with some new rules and boundaries to build a new relationship based on different values.
These may include crate training (rules) to outline a better understanding of the home / territory and what role the dog should play within that home.
Place training (rules) to help the dog develop impulse control and the ability to make choices at stimulating times.
Loose Leash Walking (rules) helps us give the dog guidance and boundaries too that help develop the relationship also.
There may be other aspects of the program but not until we have these solid would I begin to look at problem behaviours.
A dog that has learned to bite to keep a reward will not think about all options at that time, but simply go with the most successful behaviour of the past. Therefore, we need to teach some new behaviours in order to place ourselves in a better position to give the dog advice on how he or should behave in certain circumstances.
The beautiful little girl in the picture below has had a tough life, suspected born with a number of deformities, she came to us ready to bite when being touched or approached.
The first thing I did was build a bond with her of trust.

It is then that I would start adding a strategy to have the dog reframe the idea that me approaching his food should be met with guarding and aggression.
This is known as Antecedent Based Intervention and can help a dog overcome the fear of losing their food.
When we have dogs come to us for these behaviours and stay in our board and rehab programs, it can be a few weeks before we address the resource guarding.
We need to be aware that a certain person, type of person or the relationship the dog has with the person are a large part of the trigger for these behaviours.
Triggers, cues, antecedents…
These are basically pieces of information that remind the dog of a behaviour that will attract reinforcement.
Sit (cue) the dog sits (behaviour) food is given (+R).
Person approaches when dog has bone (cue) dog growls (behaviour) person moves away (-R).
Dogs that do not resource guard are not concerned about losing the food. So imagine that if you start by approaching a dog without an issue and taking food, you may create an issue.
In the line above regarding resource guarding, the “person” in the cue may be relevant, or the dog may just behave the same no matter who approaches.
The ABC’s of Behaviour, Antecedent – Behaviour – Consequence, helps us understand that each part of this paradigm are as important as the other.
The Antecedent, Trigger or Cue of you prefer, is the cause of the behaviours and can be a simple, single level trigger, or a set of triggers “stacked” to induce the behaviour.
The Consequence is something that arises out of the behaviour, you can be certain that if your dog is displaying a behaviour regularly, he or she is finding the consequence beneficial, enjoyable, reinforcing.
Whilst people come to me focused on the behaviour, a lot can be achieved by focusing on the Antecedents and Consequences.
It is important to be or become someone your dog respects and trusts before adding any intervention.

Rewards
The better and more consistently you add rewards to a behaviour, the more likely you are to get that behaviour.
It is important to realise that if your dog can access rewards all the time, for free, or by displaying a behaviour you don’t like, it will be much more difficult to get your dog to change a behaviour.
Rewards such as food or even toy rewards are most effective when you have control over when the dog gets them and when the dog loses them (+R and -P).
You can then structure training in a way that you can add rewards (+R) for the desirable behaviour and remove or withhold rewards (-P) when the dog does something we do not want.
The higher the percentage of the dogs’ rewards go into the new behaviour, the more likely a change will occur.
This places the dog in a position of becoming responsible for progress too, and allows you and the dog to team up to overcome this challenge.
Where to start
When working with a more dangerous behaviour such as aggression etc, it is wise to begin reforming a relationship with your dog on a behaviour challenge that is non-essential and not aggressive or is dangerous to anyone.
One may be teaching your dog platform training. A non-essential skill for most pet dogs but it can help you establish a relationship through communication, direction, impulse control and reward.
We use the Klimb platforms and or the Cato Boards.
It can help focus the dog on one element (the platform) and fade out the distractions in the environment.
It can allow you to establish a cue, marker training, reward delivery, impulse control and be able to give your dog direction he or she will enjoy following.
The upshot can be that your dog thinks you have some great ideas and would like to learn more of them. It is then that you may be able to tackle a more serious, in deeper seeded behaviour potentially.
If you fail to teach and train the “non essential” skill, then you would be best getting an experienced professional on board with you to help get progress.
The very large majority of dogs, even with serious issues, can improve in a relatively short period of time with the correct intervention.
They can regress instantly though if the owner does not stay the course and maintain the same level of intervention.
How to get a dog to come when she exhibits independent behavior and ignores your command.
This is a dog that may lack the motivation for the recall, due to better things on offer or just over use of the command and under payment. Best to seek out a trainer that can help