One has to remember when these tests were designed, some time ago.
Also that up to then there was no written criteria to assist those looking for a dog for a particular purpose.
Gut instinct – how valuable is that? Again that depends on the skills, knowledge, ability, training and most of all experience of the purchaser in dogs, the breed and its intended purpose.
Breeder input – how valuable is that? Depends on how much experience the breeder has with the breed, the purpose if any the purchaser and how many litters they have bred etc etc.
How valuable the test is depends on a great many factors.
First of all the knowledge and experience of the tester both of the test, the breed and of course the background of the dogs. If you know the genetics behind the majority of the dogs and have seen them in person in the context you require this is very beneficial.
Secondly how much “pre testing training” has been done by the breeder/vendor.
Testing is only a snap shot view, experienced breeders who breed for a purpose other than pet or show may well have better views and knowledge.
Many people for example misunderstand the “scary” test altogether. If a pup is not fazed by anything that the tester shows it it may be that it is deaf however you have also not tested for recovery rate. It is not whether or not a dog is surprised or not but how well and quickly it recovers which is key in assessing working dogs.
I might want a very bold pup from very shy parents in some breeds. Whereas I might not want the boldest from very bold parents in others.
The police use this test with a couple of adaptions very successfully in their breeding programmes; Steve Dean (who set up the MetPol breeding programme) added an initiative test, eg if and how quickly a dog could get to other side of barrier; problem solving is very important in both GP and sniffer dogs.
For pet purposes it is not as useful as it is say for working.
Good breeders who breed for a working purpose tend to have very even litters and will inform a potential purchaser which ones to ignore or even hold these back, much as my youngest dog’s breeder did not bother putting out the bitch puppies for me to select from knowing that I wanted a male.
I tend not to trust to luck when I purchase a dog any more than I would trust to luck when buying a house or car; I would still have a survey or credit check done…………