Just watched this clip..."We've known all along you're a psychopath, but you're a happy psychopath who doesn't hurt anyone, just likes to play with people's minds..."
Which ties into the book I'm currently reading, Clarence Pfaffenberger's "The New Knowledge of Dog Behavior" which is a 1950-something classic which outlines the early days when genetics and behavioral science combined to create very strong SOPs and bloodlines that turned guide dog training around from reject 90% of pups born to a litter to graduating 95%. The book is written in an older style so it is a bit long in the tooth and repetitive at times, none the less it is considered one of the foundations of modern dog training.
Like most things, it ends up being a combination of nature and nurture. They developed tests to pick out the early behaviors common in dogs that would graduate their programs and bred bloodlines to emphasize them, but they also learned of very critical, but short, windows to take advantage of them -- a delay sometimes of a week or two in a three month old puppy's training could double the likelihood of flunking out of guide dog training. And this was sometimes very small -- a little as 15 minutes a day (and if I remember correctly, even just one 15 minute session once a week in some cases) could make the difference during the critical psychological development periods.