I`ve owned 2 GSPs - gundogs who have been bred to be biddable (OK hollow laugh from all GSP owners but that`s the theory) Neither had any training till I got them aged 4 or 5. Neither knew how to play or scent or walk on a lead.
One responded to training like a sponge - his latent instincts worked with his desire to `do stuff` and he was a joy to work with .
Then there`s Shamus. The instinct is there - he finds and points at pheasants, no problem guv. But any training other than Come or Sit is met with total lack of interest.
The difference between the two was motivation, not breed or background. One was fixated on a ball on a rope and also enjoyed treats. The other isn`t interested in either.
Any research would need to include personality - an almost impossble task, I think.

and like us humans, we're different at different life stages . Energy depletes with age so does motivation - what motivates us as a child/teenager/young adult/middle age/old age changes throughout the cycles. Dogs are much the same.

But despite the differences, don't we just luv 'em

because of the differences we luv 'em