Even when humans anthropomorphize animal behaviors, does it mean that our assumptions are incorrect? In other words, does the lack of hard scientific evidence concerning what animals feel when they prance, play or even squeak when tickled (as rats do) mean that they're not experiencing happiness? As Karen Davis, president of United Poultry Concerns, put it, "[I]f I see a chicken with her tail up, eating with gusto (pleasure!), eyes bright and alert, I conclude that her condition is good and that she feels happy. Why should I doubt these conclusions when the preponderance of evidence supports them?" [source: Davis].
One argument in support of animal happiness is the fact that animals appear to have neurological processes similar to that of humans. Laboratory drug trials using mice have shown that they respond to the same compounds that alleviate emotional instability like depression in humans [source: Beckoff and Goodall]. What's more, to test an antidepressant's effectiveness, mice are actually made depressed through bullying from other mice. If a mouse can feel depressed, then is it out of the realm of possibility that it can feel happiness as well?
Happiness, from a strictly biological standpoint, is a form of pleasure. Why is pleasure so important biologically? We humans experience pleasure as a means of teaching us to repeat behaviors that will help ensure our survival and the survival of our species. This is the opposite of aversive feelings, like fear and pain, both of which teach us not to repeat certain behaviors. Eating food can elicit feelings of contentment or other forms of pleasure by triggering the release of hormones like endorphins. So, humans learn to eat -- which helps ensure survival -- because it feels good. The same goes for sex, which helps ensures the survival of the species through reproduction.
Proponents of the animal happiness idea argue that this evolutionary mechanism should be present in any animal with a conscious mind [source: McMillan]. Since we have proven animals experience aversive emotions like fear; logic follows that they should also be able to experience pleasurable feelings like happiness.
The argument for animal happiness remains an anecdotal -- though logical -- one. Critics of the idea still have the scientific method on their side. But what if scientists devise a test that conclusively proves that animals do experience happiness? What kind of effect would that have on our interactions with them? We don't know, but one thing's for sure: Proof that animals could feel happiness or any other emotion would present a very interesting ethical and moral dilemma for humans.