When you are looking over puppies and dogs the first thing to note is character. Dogs are bred very selectively to show certain physical and behavioral characteristics, but they cannot be bred for an individual character of their own.
Older dogs, specifically ones that aren't puppies, may leave you with the impression that they are quiet and maybe even depressed. Potentially you should consider that this dog may always have this temperament. It is also possible that after he gets to know you he will be a hyperactive showoff. Dogs that are boarded away from home frequently seem very detached. Some dogs really are softies and emotionally weak and others are sensitive yet strong.
For many dogs new people are rather nerve racking and scary. It simply takes a while for most dogs to get accustomed and relaxed enough around new people to really be themselves. Nervous dogs are just nervous dogs, although many dogs with low nerve thresholds tend to be very sharp as well. Often new dog owners will blame nervousness or apprehension on abuse. In reality the dog most likely always acted this way.
Seven or eight week old puppies that are active, outgoing and friendly are most likely not going to become fearful and nervous unless they have an extremely traumatizing experience. Likewise if a puppy is nervous at the same age, really there is no reason to believe he is going to strengthen his nerves over time. If you are trying to train a dog with fragile nerves, you're going to have to deal with it, that's their personality. If you need a retriever, pick a puppy with retriever qualities or you're going to be struggling with training your retriever.
Puppies are what they appear to be, what you see when you're evaluating them is what you'll get. Dogs are not trying to hide any secrets. The hyper female that is barking her head off will probably calm down by the time she's a senior citizen. A puppy that appears independent around you the first time, you'll be better off forgetting about him and going and finding one that shows an interest in you. The big active male in the litter
When you are evaluating a puppy, he is what he appears to be. There are no secrets. If it's a hyper little female yapping a million miles an hour, she ought to settle herself down by the time she is a senior citizen. If a puppy appears independent when you are around him for the first time, leave him behind and look for a puppy who shows interest in you. Don't choose the big active male in the litter unless you are prepared for the potential dominance and for all the time and training it could take to make him a great boy.
You can view videos and other information on Jason's favorite breed of dog - Japanese chins at http://www.ultimatechinpuppies.com