For the love of dog

Go to any park, and you will see the strange phenomenon of the canine mini-me. Maybe it's a bearded hipster, accompanied by a little bundle of fur that looks like it went to the same barber, or a pugnacious thug carrying a bulldog. Or perhaps it's an athletic jogger and her Afghan hound, their glossy locks blowing effortlessly in the wind.

Why do people choose the dog that looks most like themselves? Far from being skin-deep, the answer may give you a new appreciation of the intense bonds we humans have forged with our four-legged friends.

Michael Roy at the University of California was one of the first psychologists to put the idea to the test. Going to three nearby dog parks, he photographed the pooches and the owners separately, and then asked a group of participants to try to match them up. Despite no additional cues, he found that they were able to work out who lived with whom with reasonable accuracy. The result has since been repeated many times.

Admittedly, the result is sometimes based on superficial appearances: women with long hair are more likely to prefer dogs with long, floppy ears, and heavier people tend to have fatter dogs.

Yet, it also shows itself in more subtle features, such as subtle differences in the shapes of the eyes that are shared between pooch and person.

Maybe this is all due to the allure of familiarity: a dog may seem more comforting if it resembles the other members of our family, who we know and love. Yet some psychologists believe it might be a spillover from the way we evolved to find mates: dating someone that looks like us may ensure that their genes are generally compatible with our own. Thanks to this imprinting, we may therefore prefer anything that looks a bit like us. (Along these lines, people also tend to choose cars on the same basis -- someone with a slightly squarer jaw might prefer a car with more brutish fender, for instance.)

Importantly, our narcissism isn't just skin deep: we don't just go for people who look like us, we also tend to orbit people who share our personalities too.

A couple of years ago, Borbala Turcsan at Eotvos University in Budapest decided to test whether the same was true of our canine soulmates. “The relationship with a dog is a very special one -- they are not simply a pet but a family member, a friend, or a companion – so we thought it might develop in parallel with those other relationships,” she says.

Sure enough, Turcsan found that the dogs and their owners both tended to show similar personality profiles. "It was actually higher than the similarity found in married couples and friends," she says.

It is awe-inspiring to think of how this relationship first emerged. Humans started domesticating dogs as much as 30,000 years ago to help us with hunting, but slowly we have bred these creatures in our own image, allowing us to forge an intense emotional bond that crosses the natural boundaries between our species.

Today, they look like us, act like us, and -- unlike other humans -- they always reciprocate our feelings. In many ways they are the better reflections of our own true natures. It's little wonder we now consider them man's best friend.