Puppies hae no frear until about the 5th week of life with fear increasing gradually through 6th week and excalating toward the end of the 7th week. Between 8 and 9 weeks, overlapping the Behavioral Refinement and Enviromental Awareness Period, the puppy will begin a time of much more caution. It may be fearful of loud noises, sudden movements, strangers, discipline from other dogs or humans, etc. If frightened during this fear period, it may take weeks to return to normal. In a nonsocialized puppy, anything associated with fear at this age will always be a fearful stimulus thoughought it's entire life without extensive desensitization.