A team of Italian scientists say they have uncovered the secret emotions hidden behind different types of tail-wagging in dogs.
If a dog is happy and wants to show he comes in peace and friendship, for example, it wags its tail to the right, according to the results of a University of Trieste study.
If the animal feels afraid and wants to come across as menacing, on the other hand, it wags to the left, the team led by Professor Giorgio Vallortigara has discovered.
The biologists noticed this by observing tail-wagging when dogs were put in different situations.
They noticed the wagging lent leftwards when the dogs were faced with bigger mutts or other potential threats.
The wagging bent the opposite way when they met people they knew.
Vallortigara said this is a reflection of the fact that different sides of the dog brain control the conflicting emotions these situations provoked.
However, he stressed that the difference in the movement of a 'happy wag' and a 'frightened wag' is very difficult to spot. So his discovery may be of little help to owners concerned about their pets' emotional state.
Dogs use tail-wagging as a social signal, like the human smile, experts say.
A dog will beat its tail at a person, at a another dog or even at another animal, such as a cat.
But it will usually not wag its tail at lifeless objects when alone, because the animal knows it cannot communicate with them.
If you put down some meat for a dog, for example, it will most likely wag its tail to thank you.
If the same animal walks into a room alone and finds food on the floor, it will happily tuck in, but it is unlikely to swing its tail.
The wagging would be wasted.
The original biological function of the dog's tail is to help it keep its balance while moving fast or walking on narrow surfaces, as with other animals.
The University of Trieste study is published in the latest edition of leading international life sciences journal Current Biology.
