Share 'Addiction to shadows'

My friend's dog - german shepherd is addicted to shadows. It's one year old fit dog. Everything is fine but looking all the time (when is light) at shadows -  peoples, things', plants', other animals', his own. This is quite tiring for him and for his owners.This dog all sunny days  works - he tries to catch the shadow, eat it, lick it.  He can't lie down and rest. The same is at home in the even…