Dogs Also Get Nervous
A dog's nervous system is, in general, extremely sensitive and even fragile, butdon't develop psychosis or mental diseases like humans do. However, a dog can be neurotic or neurasthenic.
In general, a nervous dog shows signs of agitation when an unusual incident is perturbing him. He doesn't adapt to new situations easily, he hides when there are new noises; in the street he is uneasy and tries to bite anything that moves – motorbikes, for example. But by educating the dog to obey you can attenuate his nervousness.
It is easy for a stray dog to be nervous; most likely he has encountered many difficulties throughout his wanderings in the street. His instinct of conservation has helped him stay away from anything that might cause him harm. The most common thing is for the fear to manifest when there is the sound of gunfire, thunder, a storm, firecracker, and/or any other loud noise like sirens or megaphones, but it can also manifest when entering new and silent places.
Fear can be congenital, in other words, part of the animal's psyche since conception or acquired later, which is usually the case of stray.
In the first case, it is difficult to treat, but in the second, if you are very patient, you can obtain excellent results.
The fear of gunfire, for example, can be cured by asking a friend to shoot a blank shot while you hold the dog in your arms and pet him softly, as well as giving him a tempting delicious treat. You can do something similar to get him used to other kinds of loud noises.
But you'll have to take precautions when dealing with extremely neurasthenic or traumatized(Street frequently belong to those categories) which could run away in a fright.