Even tho it's not explicitly listed anywhere, there is a moral calculus that goes on in everybody's head when weighing the value of a life. Why do most people say that if forced to choose they would save the life of a 7 year old over a 97 year old? Because we judge that the potential is much greater for the 7 year old. If given the same choice between that 97 year old and a 1 year old dog, most people probably choose the 97 year old. The age is irrelevant in this scenario because we value human life over canine life.

If you follow this chain down, we value dog lives more then chickens. Dogs have lived with us as domestic companions for millennia. Dogs have an almost unique ability to read human emotions, and infer what we want. They are loved as pets we indulge and they can be put to work as herders, guide dogs and police dogs. Chickens on the other hand do not enjoy such a lucky existence. We eat chickens and exploit them in several ways, but we certainly don't kill them for no reason. The reason for their existence (at least from our perspective) is food. So in this moral judgement that we do, the dog's life is valuable, whereas the chicken's life is not.

&nb… — "Fair's fair, Larry. We drew straws and you lost."