Sam The Dog Trainer - Dog Training - Behaviorist

Interesting

A newly discovered feature of dog body language that may surprise attentive pet owners and experts in canine behavior. When dogs feel fundamentally positive about something or someone, their tails wag more to the right side of their rumps. When they have negative feelings, their tail wagging is biased to the left.

I haven't noticed this before. I will have to start watching. Might be a very useful dog training idea.