By Kayla Causey & Aaron T. Goetz

"I hate how they're so cute. I hate it!" -Ryan Moyer, social psychologist and eternal skeptic

We think we're so smart. As humans, we have succeeded in manipulating the environment to meet our needs, a feat unique to our species. So we think...

What we might not realize is that we've created a monster who, without even saying a word, manipulates us into willingly relinquishing to it all that we have created. In our state of lowered blood pressure and oxytocin-induced euphoria, we brag how well we have trained it while we pamper it in spas, buy it expensive clothes, and push it around in plush prams from one gourmet bakery to the next. Many of us even sleep next to it every night. And we're convinced it's our best friend. An alien species from another planet? Hardly. Last year, most of us called them "Molly" or "Max" - In decades past, they came running to "Fido" and "Rover." That's right, we're talking dogs. Canis lupus familiaris.

Artificial selection for these four-legged friends began roughly 15,000 years ago, resulting in hundreds of breeds who get smarter and more social with every in-bred generation. A particular preference (or selection pressure) seems to be for dogs that are smaller, cuter, and remain puppy-like even into adult maturation. In other words, there seems to be an influential preference among humans for adult dogs that possess neotenous features, much like those we prefer in human infants, including large communicative eyes (especially with visible white sclera showing, see photo below), and small noses and mouths.

Not only do we prefer animals that are physically neotenous, but we also might say that many dogs are selected based on their ability to behave in a way that parasitizes parenting mechanisms. These once viciously carnivorous wolves have physically and behaviorally morphed into altricial beings that compel us to throw them birthday parties, brush their teeth, buy them clothes, and spend more money on their haircut than we might spend on our own. In other words, we invest in them as we would our own flesh and blood children. Clever beasts.

Evolutionary psychologist John Archer, of University of Central Lancashire in England, was the first to offer a solution to this Darwinian puzzle. He recognized that the time, effort, and resources that humans spend on dogs are barking mad, from an evolutionary perspective. He argued that pets (particularly dogs and cats) could be thought of as "social parasites" that manipulate human responses. That is, dogs have tapped into the parts of our brain associated with parenting behavior. Forget shaking, sitting, and rolling over; dogs' greatest trick is their ability to parasitize our parenting psychology.

Strikingly, our pseudo-nepotistic tendencies seem rooted much deeper than public displays of affection (and/or wealth), but may actually have a biological basis! We have outwitted ourselves... Biologists Miho Nagasawa and Takefumi Kikusui, of Azuba University in Japan, demonstrated that humans release oxytocin after playing with their dogs or just simply gazing into their dog's eyes. The natural release of oxytocin in humans has been shown to facilitate maternal and pair bonding, lactation and breast feeding. It's also what doctors inject in women to induce labor. The release of this chemical when we gaze upon our hound strongly suggests that our parenting mechanisms are being parasitized by these mongrels: Our biology is kicking in and telling us it's time to invest and parent, and even though we know that these animals are not actually our biological offspring, we often can't resist the urge to envelop them with affection (and sometimes kisses). No wonder motherese (or baby talk) is also directed to pets.

The relationship does not seem to be one-sided, however. J.S.J. Odendaal and R.A. Meintjes, of Pretoria's Life Sciences Institute in South Africa, demonstrated that dogs also experience a rush of oxytocin and dopamine, among other neurochemicals, after a brief period of petting. This suggests that dogs, much like children, have an emotional response to their caregivers' affections.

We are unaware of any studies that have indicated humans release oxytocin after interacting with other types of pets, such as cats. It may be that dogs are especially able to parasitize our parenting mechanisms because of their advanced social cognitive abilities, relative to other domesticated species, which facilitates their interaction with humans. Because wolves, dogs' distant ancestor, are pack animals, domesticated dogs are social by nature and thus, with a little tweaking from humans, have evolved simple theory of mind abilities, such as social referencing (i.e., they can make use of their owner's pointing to discover the location of food or toys). Dogs also seem capable of making use of these perspective-taking abilities when dealing in deception: Food scraps will remain on your table until you're not looking. Thus, it may be that during the process of canine domestication, dogs came to share the same social cues as humans, facilitating their adaptation to our society. Or just manipulating us to catalyze theirs.

Suggested Reading and References

Archer, J. (1997). Why do people love their pets? Evolution and Human Behavior, 18, 237-259.

Nagasawa, M., Kikusui, T., Onaka, T., & Ohta, M. (2009). Dog's gaze at its owner increases owner's urinary oxytocin during social interaction. Hormones and Behavior, 55, 434-441.

Odendaal, J.S.J., & Meintjes, R.A. (2003). Neurophysiological correlates of affiliative behaviour between humans and dogs. The Veterinary Journal, 165, 296-301.

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