Jeremiah says: "The New York Times reports that dogs wag their tails in an asymmetric manner to demonstrate whether they have positive (calm and happy) feelings about what they see or aggressive and negative. Left is negative, right is positive. A lot of brain research says this makes perfect sense, but no one had studied it before."
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.
