I know it may sound odd, but the person i was buying a puppy from would play a big role aswell, there are maybe a couple of breeders i have seen post that, although their pups are lovely and perfect 'standard', i would never want to buy from, and then there are others who seem to be so warm and friendly and knowledgeable that i would jump at having 1 of their pups. i just think that if a person comes across as likeable and warm then the pups would have picked up on that!
Thankfully majority on here fit the 2nd category so maybe its best i'm in England and can't fill my home with all these YT puppies.
btw.. a lie detectors a brilliant idea lol