Under what circumstances will make a dog afraid of people？

1.Was abandoned.
2.Has been abused.
3.The teaching of the same kind is far away from human beings.
These three points are the main reasons why dogs are afraid of people. Among them, abuse takes the largest proportion, because it will leave dogs physical and mental trauma, and there is a certain degree of irreversibility.

In particular, psychological trauma will stimulate the emergence of emergency instincts, and then the temperament will become irritable and easy to attack, or even more timid and fearful of extremes.

Abandonment will turn the dog into a "stone waiting for its owner", just like a loyal dog Hachiko, staying at the place where it last saw its owner, during which no one is allowed to approach it. Because it is afraid that if it is taken away, it will never be able to wait for its owner.

It is also derived from the above two factors that teach puppies to stay away from humans. Because older dogs are unwilling to bear this pain for younger generations, dogs who live with the same kind will be even more afraid and distrustful of humans.

To put it plainly, dogs are afraid that humans are basically man-made evil, otherwise, how can dogs who have been domesticated and screened by humans for thousands of years actively fear humans?