My 2 year old Sheltie mix is like two different dogs...when we're at my parents house, he's fine, doesn't bark at the cars or other dogs; but when we're at my apartment complex he seems more aggressive. He'll bark at the cars, won't play nice w/ other dogs, tries to chase things down, etc. Anyone have any suggestions as to why I've got Dr. Jeckyl and Mr. Hyde??? He can be perfectly fine off the leash at my parents house, but I wouldn't think of it at my apartment. Anyone else have something like this? Any suggestions would be welcome. Thanks in advance!