Dogs go through two stages of fear naturally, its part of their development. The first stage of fear happens between 5 and 7 weeks old and lasts for two weeks. Most dogs come through this stage without any problems at all. The next stage of fear happens between 5 and 8 months (depending on breed). This episode lasts for two months and normally subsides without any problems. This is all normal and may not even show up as fear in a dog. In the the fist stage of fear i.e 5 to 7 weeks the puppy is with its mother and siblings so nothing should go wrong there. In the second phase of fear at 5 to 7 months that is when things can, and do go wrong. During this stage most dogs are capable of pushing through this stage without any problems. Those dogs that are mistreated, handled badly, abused, neglected, trained badly etc will be fearful for the rest of their lives and will need special care. It is so important to know this and yet no such advice is ever given. Yes, people say at puppy stage 'you must socialise your dog' but normally that's it. There is a lot more to it than just socialisation.