PUPPY vs ADULT:
All puppies are cute and a lot of them are just a little bit pathetic. These physical attributes tug at our heart strings. Don't let that fool you. Puppies don't stay puppies very long. Try to remain objective.
Puppies are a lot of work. It takes at least 18 months to raise a puppy; to guide and shape him into the dog you want him to be.
Puppies jump up and nip, pull hair, grab and tear clothing, and steal things from children. This behavior can be very intimidating, even frightening, to young children.
Puppies will go through numerous developmental stages, which interfere with training and are likely to cause you numerous set backs.
It is almost impossible to predict a puppy's adult behavior. Puppies are no more like an adult dog, than a toddler is like an adult human.
The benefits of buying a young puppy are: young puppies are easily trained and because their period of social development has not yet passed you have the best chance of socializing your puppy to your environment. This is particularly important if you have young children or cats or other pets.
Puppies over 18 weeks of age, but younger than 7 months of age, are not going to be as easy to train as the younger puppies. However, there is a secondary learning period you can capitalize on at around 6 months of age.
Adolescent puppies, those 8 - 15 months of age, are more difficult to train. They are in a developmental fear period, the secondary learning period has past, and any unwanted behaviors have been well rehearsed by this time; all of which contribute to training difficulties.
Any adult dog or older puppy who has not had some training early on is going to be harder to train than a dog who has had some early training.
Any adult dog or older puppy who has not been exposed to enough people, places and things, in a safe and positive way, before roughly the age of 16 weeks, is likely to have difficulty adjusting to those things and may behave fearfully around those things all of its life. The optimal period of social development for a dog runs from 3-12 weeks of age, with a little wiggle room until around 16 weeks of age. After that, learning and social conduct may never be as easy or good as they could have been.
Future adult dog behavior is a little easier to predict than it is to predict a puppy's adult behavior. You will certainly see behavioral changes about every three weeks for about 6 months, but the benefits of an adult dog are: a nice dog is going to be a nice dog once he has settled into your home; a dog who is known to be good with children or other animals is likely to remain so once in your home.
Stay tuned for part four: Where To Buy Your Dog