Tell-tale signs show owners what's going through their dog's mind

Almost everyone knows that if a dog is wagging its tail it's happy, right? Wrong. Being able to read what your furry friend is thinking and feeling takes more than a simple wag.

'A common misconception is that a dog wagging its tail is a happy dog, but that's not at all the case. It depends on a variety of things,' says Stanley Coren, psychology professor and neuropsychological researcher at the University of British Columbia, and specialist in the intelligence and mental abilities of dogs.

Tail wagging, Coren says, can be broken down into the speed of the wag, size of the swing and elevation of the tail.

For example, a dog that is not feeling well may wag its tail slowly, hold it very low and sway in small movements. Alternatively, when a tail is held very high and moving back and forth at a swift rate, the speed is usually due to excitement and happiness.

However, the professor details another scenario: 'When the tail is high with short movements, the dog is basically saying, 'I'm the boss around here, so give me some space'.' He adds this latter tail wag is a warning to beware as the dog may be ready to snap at a hand or person.

Another way of quickly assessing a dog's emotions is to see its tail as a thermometer with mercury that rises and falls - dominant tails are hot and high, while low tails are cold and frightened. A relaxed dog has a lightly drooping tail that isn't stiff.

If you want to be sure your dog is happy, Coren says look for your dog's tail held moderately low with big swings that seem to drag the hip from side to side. 'This is the dog's 'you are my fearless leader tail wag' that shows he is very submissive. The dog is thinking you are my leader and you will not hurt me,' says the Vancouver-based professor, who wrote The Intelligence of Dogs.