My 1 year old golden retriever has new obsessions of shadows. At first we thought it was a phase but now it's to the point of him biting the walls and ramming his head into the ground to get the shadows. He will even do it in a pitch black room. We don't know what to do.

Sounds like you need to give him LOTS MORE exercise.

Bored dogs, or dogs left home alone a lot will develop strange behaviors in order to entertain themselves.

Take him on one more walk, take him to the dog park more often, take up hiking/jogging/cycling.. make your dog tired.

Unless he is a tired dog and has other outlets to release this energy, he is not going to give up this habit. Even if you are exercising him regularliy.. amp it up. He's telling you he is bored!

You haven't been using a laser pointer by any chance, have you?