Deborah Bird in EarthSky writes: A dog wagging his tail to the right is happy, but a dog wagging to the left is stressed.
To see the science behind this, a report is in ‘Current Biology’. Not only does the direction of wag give a clue to how the dog is feeling, it can also influence how other dogs feel too. ‘Seeing Left- or Right-Asymmetric Tail Wagging Produces Different Emotional Responses in Dogs’
It’s not surprising that other dogs can read ‘tail’ language and may respond accordingly – just as when someone smiles at us we may smile back. If someone looks agitated, then this will affect how we feel towards them also.
Not only the left or right direction of the wag has something to say, so does the speed, height and combination of movements mean a lot also. Too many people have been bitten thinking that a wagging tail means a dog is pleased to see them and wants to be touched.
Here is my story of two Labradors who illustrate perfectly that wagging to the right means happy:
Theo Stewart, The Dog Lady
Go to the main website: www.dogidog.co.uk
Paws for Thought 