This is untrue. Dogs do look up. What is in question is whether dogs *should* look up. Particularly, should BOTH of them look up at a squirrel in a tree while racing around the tree, hoping the squirrel will come down.
If the dogs wish to avoid a rather painful high-speed collision, my verdict is that at least one of the dogs should try looking where he or she is going. Both dogs have now retired to their beds nursing their bruises.
*Shaun of the Dead.