//”But it raises questions like how did they determine if the dogs, they used, are aggressive?”//
GREAT GREAT QUESTION!!! Loved it! Science DOES much love to quantify, measure, and be very precise and exact, so your question, how DID they decide which dogs are aggressive, is a most excellent and thoughtful question, one which I DID post a link to, a test used by veterinary scientists to decide which dogs were to be included as aggressive dogs.
(actually, having many scientist pals, i know, scientists MUCH love to crack on each other, if one is seen as NOT adhering to "The Scientific Method", whihc is worth a google if you are not science buff, to get idea of HOW science determines what data means or does not mean)
The researchers focused only on otherwise healthy dogs who had lifelong ongoing, permanent aggression, which was not amenable to rehab/training/etc.
Here are a few links, from a researcher team, doing tests to sort out which dogs will be considered aggressive dogs:
using an agression test: (done in the Netherlands!)
using a questionaire:
Researchers at Texas A&M coolege of veterinary medicine, comparing owner complaints vs what they see in their behavior laboratory: (not exactly the same thing as you asked about, but interesting jsut the same)
and this one
Ahh, now I get it! Shouldn't be reading when I'm supposed to sleep...I did read that first post, but it didn't sink in, I guess.