Have you noticed the phenomenon of puppy dog eyes, the inner eyebrow raising movement of dogs? Do you believe it a result of 41 for dogs to appeal to humans? Researchers dissected dog and wolf heads and found that the facial muscle anatomy of both animals was almost identical -- ____ an eyebrow muscle, found only in dogs. The inner eyebrow raising movement makes the dogs' eyes appear larger and more infant like, 43 prompts a "nurturing" response in humans.