Dogs talk with their tails

We know that a dog wagging his tail means "I am so happy to see you!".
But did you know that the dog is expressing different feelings depending on which direction the tail is wagging?

This newly discovered feature about dog body language was presented in the study "Asymmetric tail - Wagging responses by dogs to different emotive stimuli" in a issue of Current Biology.
When dogs feel fundamentally positive about something or someone, their tails wag more to the right side of the rumps. When they have negative feelings, their tail wagging is biased to the left.

Pictured below are some dogs playing in Peters Park in Boston. How are they expressing their feelings towards each others?



The dog Jack and his owner in Newton. Does the body language and the direction of the tail-wagging of the dog express the same feeling?




Read more about this phenomenon in the Herald Tribune's article by Sandra Blakeslee:
http://www.iht.com/articles/2007/04/24/healthscience/snmood.php