Dog Traits, Including Shyness, Have Implications for Human Longevity

Scientists knew that dogs were breed for different tasks, but new research shows that traits like activity or aggression needed for those tasks may influence a dog’s lifespan – a finding that may be key in unlocking the mysteries of our own lifespan.

By domesticating dogs, humans unwittingly initiated an artificial selection experiment on personality – the results of which may have implications for our own longevity.

We know that dogs were breed to specific tasks and that individual dogs were selected for reproduction based on certain behavior traits – such as activity, aggressiveness, and docility – related to those tasks.  Today those traits are recognized at dog shows by categories like Sporting, Working, Herding, and Toy and dogs within those categories are recognized for their skills at retrieval, guarding, herding, and human companionship.

But it’s assumed that other traits, such as longevity or energy expenditure were probably not targeted for selection.  Now researchers are finding correlations that suggest metabolism and lifespan changed as by-products of selection on personality traits.  These connections between behavior, metabolism, and longevity have resulted in a “pace-of-life” syndrome hypothesis.

A team led by Vincent Careau, a PhD student at University of Sherbrooke, gathered data on many aspects of dog biology published in such disparate fields of study as psychology, longevity, and veterinary research. While the information was well known within the respective research domains, it was never put together. By combining findings, the authors show that obedient breeds — on average — live longer than disobedient breeds, but aggressive breeds have higher energy expenditure.  As the late naturalist Don Thomas said, “It is hard to imagine how an aggressive personality could be adaptive if it lacked the energetic and metabolic machinery to back up the threats. Simply put, 100 pound weaklings don’t kick sand in weight-lifters’ faces and survive in nature.

This study, published in the June 2010 issue of the American Naturalist, is significant because it contributes to the growing body of research that shows that personality is related to many crucial aspects of an animal’s life – including energy needs, growth rate and lifespan.  It also brings scientists a step closer to understanding evolutionary causes and consequences of different personality types and may someday be a key in unlocking what determines our own lifespan.

Dogs Show Their Feelings Through the Direction of Their Wags

New studies show that your dog's tail wag tells a lot: a wag to the right of its body shows positive emotions; to the left negative.

Imagine if your dog could talk. What does he really think of your new boyfriend? How badly does he want to go nose to nose with the overaggressive dog at the park whose owner assures you just loves everybody?

Most dog owner will look at their dog’s posture for some clue, and consider a wagging tail one of the best indicators. But which way is it wagging?

Dog’s tails fall in the mid-line of their bodies, neither to the right or the left. Now researchers in Italy have discovered that when dogs feel fundamentally positive about something or someone, their tails wag to the right. When they have negative feelings, their tail wagging tends left.

Giorgio Vallortigara, a neuroscientist at the University of Trieste in Italy, and two veterinarians, Angelo Quaranta and Marcello Siniscalchi, at the University of Bari, also in Italy, recruited 30 family dogs of mixed breeds that were enrolled in an agility training program. The dogs were placed in cages with cameras angled to precisely track the direction of their tail wags. Then they showed the each dog four stimuli through a slat in the cages: the dog’s owner, an unfamiliar human; a cat; and an unfamiliar, dominant dog.

When the dogs saw their owners, their tails all wagged vigorously toward the right side. Their tails wagged moderately and more to the right, when looking at unfamiliar human. When faced with a cat, the dogs’ tails again wagged more to the right but in smaller sweep.
When viewing an aggressive, unfamiliar dog – a large Belgian shepherd Malinois – the dogs tails all wagged to the left side of their bodies.

“This is an intriguing observation,” said Richard J. Davidson, a neuroscience researcher at the University of Wisconsin in Madison.  Not surprisingly, the findings play up some of the fundamental differences that have been shown between the left and right brain in humans — research that has been replicated in other animals.

In most animals, including fish and birds, the left brain deals with behaviors scientist term approach and energy enrichment. In humans, that means the left brain is associated with positive feelings, like love, or a feeling of safety and calm.  The opposite occurs in the right brain with behaviors involving withdrawal and energy expenditure. In humans, these behaviors are associated with fear or depression.

The study which appears in the March 20 issue of Current Biology, suggests that the muscles in the right side of the tail reflect positive emotions while the muscles in the left side express negative ones.