As my two are getting older they seem to be finally getting a little braver. Trevor pretty much isn't afraid of anything. He will leave the room if the vacuum cleaner or the hair dryer is being used but I think at this point it is more out of disgust for me disturbing his peace. Andy is afraid when people knock on the door. He quickly runs down to the basement and if he recognizes the voice he comes right back up. If not he will wait until "the voice" leaves. I have seen him wait for over 7 hrs.