Dogs' behaviour - it's all in the wag
By Roger Highfield, Science Editor
Dogs wag their tails to the right when they see something familiar, such as their owner, and to the left when confronted with something they want to run away from, it was revealed yesterday. The bias is subtle, requiring video analysis to spot, and not obvious enough for you to tell whether the next dog you meet is going to lick your face or turn tail.
But, researchers suggest, the study of wagging could be used in animal welfare to help vets to gauge an animal's state of mind.
Prof Giorgio Vallortigara of the University of Trieste, Prof Angelo Quaranta and Dr Marcello Siniscalchi of Bari University, tested 30 male and female pet dogs of varying breeds recruited from an obedience school. They filmed each dog's response to being shown either their owner, a human stranger, a cat, or a Belgian shepherd malinois, a large breed similar to a German shepherd.
Shown a human, tails wagged consistently to the right. They carefully studied the tail wagging angle and ignored twitches of less than three degrees overall, "which were plausibly not correlated to wagging".
They found that the unfamiliar person elicited less wagging than the owner, and the cat the least wagging of all, though still slightly to the right - probably because the dog was so keen to give chase that it was distracted.
Shown a large, unfamiliar and intimidating dog, the dogs wagged their tails more to the left.
Dogs also wagged to the left when on their own without anyone to look at, suggesting that they like company, according to the study in the journal Current Biology. The finding provides another example of how the right and left halves of the brain do different jobs in controlling emotions. Studies have shown that, in humans, strong activity in the left hemisphere (which controls the right side of the body) is associated generally with a sunny disposition. Human studies have also linked left-brain activity with approach behaviour, and right-brain activity with retreat.
Dogs are already known to prefer to use one paw over the other - most male dogs are left-pawed, whereas females show a lesser tendency to right-pawedness.
But what they do with their tails may be a better guide to how their brains work, Prof Vallortigara said. "Tail wagging is an important emotional response," he added. Biases for right- or left-handed behaviours have been seen in amphibians, reptiles, birds, fish and mammals, suggesting that brain asymmetry is ancient, he said.
A spokesman for the Kennel Club said it was well known that dogs wag their tails when they are happy.
From now on, she added, she would take more interest in the direction of the wag.