April 24, 2007

the science of tail-wagging

[Picture: The Center for Neuroscience, University of Trieste]

Animals' brains may be organized as asymmetrically as humans'. The left brain - which controls the right side of the body - specializes in behaviors involving positive feelings, while the right brain - which controls the left side of the body - specializes in "behaviors involving withdrawal and energy expenditure". Being located in the middle of the body, a dog's tail may be controlled by both hemispheres. The New York Times reports a study that looked at directional wagging patterns:
To find out, Dr. Vallortigara and his colleagues recruited 30 family pets of mixed breed that were enrolled in an agility training program. The dogs were placed in a cage equipped with cameras that precisely tracked the angles of their tail wags. Then they were shown four stimuli through a slat in the front of the cage: their owner; an unfamiliar human; a cat; and an unfamiliar, dominant dog.

In each instance the test dog saw a person or animal for one minute, rested for 90 seconds and saw another view. Testing lasted 25 days with 10 sessions per day.

When the dogs saw their owners, their tails all wagged vigorously with a bias to the right side of their bodies, Dr. Vallortigara said. Their tails wagged moderately, again more to the right, when faced with an unfamiliar human. [...]

When the dogs looked at an aggressive, unfamiliar dog — a large Belgian shepherd Malinois — their tails all wagged with a bias to the left side of their bodies.

Thus when dogs were attracted to something, including a benign, approachable cat, their tails wagged right, and when they were fearful, their tails went left, Dr. Vallortigara said. It suggests that the muscles in the right side of the tail reflect positive emotions while the muscles in the left side express negative ones.
If your dog wags to the left if he sees you, there's still hope. Perhaps he is a leftie and his hemispheres are wired conversely.

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