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—What I have found in my latest search, is information that these dogs have been bred for brain abnormalities.

“. . .abnormal disinhibited behavior is not functional, and it is unpredictable. Although high arousal and sudden attack can be functional in certain environments, this behavior is pathological in a safer environment, where a high level of arousal and aggressiveness are not necessary and only lead to unnecessary attacks and injuries. Research implicates the frontal cortex, subcortical structures, and lowered activity of the serotonergic system in impulsive aggression in both dogs and humans. Impulsive aggressive behavior in dogs seems to have a different biological basis than appropriate aggressive behavior.

Kathelijne Peremans, DVM discovered this by studying two different populations of impulsively aggressive dogs. Each dog had executed one or more attacks without the classical preceding warnings, and the severity of the attacks was out of all proportion to environmental stimuli. Peremans found a significant difference in the frontal and temporal cortices of these dogs, but not in the subcortical areas, compared to normal dogs. Peremans also found significant dysfunctions of the serotonergic systems among these dogs.

(Excerpt from book: The Science of How Behavior is Inherited in Aggressive Dogs)(Semyonova)

The above and below are from an article on Semyonova’s book, written by Merritt Clifton, link here: http://www.animals24-7.org/2015/11/10/the-science-of-how-behavior-is-inherited-in-aggressive-dogs/

Continued:

Behavioral conformation

But breeders also selected for behavioral conformation. To perform well, a fighting dog had to attack without provocation or warning, and to continue attacking regardless of the response of the other animal. Bull and bear-baiting dogs had to be willing to attack in the absence of the species-specific signs that normally provoke aggression, responding to the mere presence of another animals, and not stopping in response to external stimuli. The Dogues du Bordeaux used to guard extended farmlands in France, the Boerbulls used similarly in South Africa, and the fugitive slave-chasing dogs of Latin America, such as the Dogo Argentino and Fila Brasiliero, all were selected to specifically for a propensity to kill.

As they selected for performance, breeders could not know exactly which physical changes they were selecting for. But research now shows that selection for aggressive performance includes consistently selecting for very specific abnormalities in the brain. These abnormalities appear in many breeds of dog as an accident or anomaly, which breeders then attempt to breed out of the dogs. In the case of the aggressive breeds, the opposite occurred. Rather than excluding abnormally aggressive dogs from their breeding stock, breeders focused on creating lineages in which all the dogs would carry the genes causing them to reliably exhibit the desired impulsive aggressive behavior.

“That aggression is not heritable is not tenable”

Now that we know exactly which brain abnormalities the breeders of fighting dogs have been selecting, the assertion that this aggression is not heritable is no longer tenable. It is also not tenable to assert that not all the dogs of these breeds will carry the genes that make them dangerous. These genes may occasionally drop out through random accident, just as golden retriever may acquire the genes to be impulsively aggressive. But the failure to have these genes, in the aggressive breeds, is just that––a failure. It is therefore misleading to assert that the aggressive breeds will only have the selected genes as a matter of accident, or that most of them will be fit to interact safely with other animals and humans.

As in the pointer, the husky, the greyhound, and the border collie, the genes of aggressive breeds have been selected so that certain postures and behaviors just simply feel good. These dogs will seek opportunities to execute the behaviors they have been bred for. Because these behaviors are internally motivated and rewarded, they are not subject to extinction. Learning and socialization do not prevent these dogs’ innate behaviors from appearing.