my friends 20month old bichon has a problem around other dogs, mainly bigger dogs, who if they retaliated back would probably do a lot of harm to him.  some days hes great then hes a little terror. he ll go for them, he hasnt bitten any just shows his teeth etc. he is used to being around dogs and this has just began happening in the last couple of months.  is it his age? is he saying  im a man? dont mess with me. will he grow outof it when he reaches 2 years as some people have said.  can anyone give me advice , my friend will be very grateful.  hes is so placid at home, you can do any thing with him, hes just jekyll and hyde maybe?::confused