ooh this is a neat line of research. my young (just shy of 3yo) border collie x australian cattle dog shows a fear of novelty (she’s also very wary of dogs with pricked ears, especially if they are white, have blue eyes or stare at her). she also guards me and i am HER human. i’ve had her since she was 13 weeks old and worked hard to socialize her since we do agility together. despite my best efforts, she has these issues. they cause me a bit of management trouble when we’re out and about.
i’m sure there are many factors in this (including me!), but the genetic component is interesting to me. i wonder if the more wolf-like a dog is, the shorter these critical periods are. certainly she wouldn’t be the first wary cattle dog, and indeed i’d say she’s more cattle dog than BC between her ears.