Temperament tests must be done in a place that is new to the dog. This is expressed in the desire to chase moving objects, seek out hidden objects and carry objects. This drive is essential to all scent work and off lead apprehension work. Even young puppies should chase toys and follow moving objects. The dog is approaching maturity at this age and shows most if not all of its temperamental traits.
Maturity varies with breeds and individuals.
Sometimes a dog which is not fully mature will not show a mature defense or dominance drive but would be suitable for training if trained carefully or allowed to mature before training. Even if this is so, enough of this drive should be present at 20 months to 2 years for an experienced evaluator to determine if the dog is a candidate or not. Someone familiar with the breed being tested will make the best evaluator. Evaluating puppies and immature dogs is much harder because they tend to show submission to people and this will repress their defence and dominance drives. Someone who is familiar with the parents, ancestors and possibly siblings from earlier breedings and has raised and trained many puppies has the best chance of predicting whether or not a puppy will be a good working dog.