While playing games, they practice different physical stances, learning their significance and the effect that they have on others. They learn what to bite and to be bitten and the sense of the different kinds of barks. This training moderates their own desire to bite and to bark.
Puppies are educated by the mother in a way that they learn to accept discipline. If a puppy didn't learn to accept leadership in his interactions with other dogs of the litter, his training would be more difficult later. Puppies who are separated too early from the nest, will have a tendency to be more nervous, bark and bite more and also to be less receptive to discipline. Often, they are more aggressive with other dogs. In general a dog who is sold to a pet shop or introduced to a new home before the age of seven weeks won't achieve his full potential as a good dog and companion.
This is the best time to introduce a puppy into his new master's home. During this time, let the puppy get to know the situations and things that will have an influence on his future life. For example, if you want him to interact peacefully with farm animals or with a cat, this is the time that he should meet them positively and not as a threat. If the breeder didn't already get him use to noises, like a vacuum cleaner, motor, traffic, etc., it is during this period that you should do it. You should also introduce him to different people: children, men with beards, women with big hats, elders, etc.
At seven weeks the puppy's brain has reached its full maturity. However, his capacity of concentration has not yet fully developed and his attention span is shorter. But, he can learn! Not only what is taught him but what he sees around him. At this age the training is easier. Everything he comes into contact with will make a permanent impression on him. Behavior taught at this age will be permanent. It is important to remember that your puppy will grow and anything that you will not tolerate later must not be accepted at this age. This is also the best age to start the training in a non-punitive way, taking into consideration his physical limits and his short capacity for concentration.
From eight to eleven weeks: the impregnation of fears
During this period, all bad experiences, all pain or scary experiences will have a greater effect on your puppy than if they happen at any other moment of his life. For example: a visit to the veterinary clinic that turns out to be unpleasant, could make your puppy anxious for future visits. To avoid this, bring toys and small rewards that you can give when you are in the waiting room. Ask your veterinarian to give him small treats and especially to give him a lot of hugs and congratulations after having done the examination and vaccinations. Under no pretext, should he have surgery during this period, like the cropping of the ears or any other, except of course, by absolute necessity.
In general, avoid stressful situations and continue to socialize and to train your dog in a positive and non-traumatic way.
This critical period is also known as being the age of cuttings (meaning separation). It's at this age that your puppy will begin to verify who will be the chief of the gang. From twelve weeks, if your puppy tries to bite you, even while playing, or bites the leash while walking or during training, it is generally a sign of domination. The habit of biting should be completely and absolutely discouraged from the age of twelve weeks.
Serious training, if it hasn't already begun, must be started now. It will be easier for the dog to realize that you are the master. When you assume the responsibility to buy a dog, you also assume the responsibility to train him and to become his master. By training and some specific exercises, you will learn to become the chief of the band.
The above is generally the same for all dogs, without consideration for the breed or the size of the dog. The next critical stages will fluctuate depending on the size of the dog and at what age they will reach maturity. In general, small dogs experience these stages earlier than big dogs for which the development is slower.
From four to eight months: escaping period
This is the age that your puppy will "test his wings". He will run away and become completely deaf to your calls. If this arrives during a training period, the dog's answer to the command "come" will probably be to run away in the opposite direction. Now that you know, you will be able to say AH! HA!, this is the escape instinct.
This period generally persists for a couple of weeks to one month and depending on how you handle your dog, it will make the difference between a dog who comes or not when you call. During this period think about attracting him positively, rewarding him generates an even stronger interest than the one that draws him away. Too many people make the mistake of punishing them for escaping right after they come back, the only thing the dog will remember is: to come = punishment. This fact will cause you a lot of problems later.
However, until you are sure of your dog, keep him on a leash. Don't give him any chance to run away, if you don't do this, it will only encourage his bad habit.
From six to fourteen months: second period of fear.
This second period of fear are not as definite as the first. She is marked by the hesitation of your dog, that is now a teenager, to become familiar with a new situation or its sudden fear owing familiar thing.
To be able to better cross this period, be patient, be kind, don't force your dog to make something who fear him. Tempt again to demonstrate him patiently that is no reason to justify his fear, permit him to face them positively. Over all continue your trainning on the same way, to procure him a certain leadership on a reassuring and familiar manner.
From one to four years: maturity
This critical period is often marked by a growth of aggressiveness and by a new testing of your leadership. 
The increased aggressiveness is not necessarily negative. It means that your dog, who until now was super friendly, will become a good guard and will bark if someone comes. It can also explain why 2 dogs who were good friends, can no longer get along when they meet.
If at maturity, your dog tries again to test you, handle him firmly and continue the training. Train him regularly during this period of testing, encouraging him if he answers correctly to your expectations.
Many dogs don't show a noticeable change during this period, but if it does happen, you will be prepared and will be able to understand what is going on. Don't be afraid, use the same training methods you used before with all the firmness you need. You and your dog will go through this period with no serious problems.
