By Nan Talleno

PHILADELPHIA (CBS) – It’s long since been accepted that a wagging tail is a sign of a happy and contented dog. While that certainly can be the case in many instances, you must first look at the context in which this happens – as in all body language which expresses communication.

When a dog is calm and relaxed and even happy to greet you, this certainly applies. But when a dog is in alert mode or begins to become overanxious or overexcited, the tail can also wag but extremely quickly.

Research has determined that a tail wags primarily to the right when a dog is in a more relaxed and contented state such as greeting familiar people and other animals and that alternately, a tail wagging predominately to the left may indicate stress or anxiety due to approaching stimuli that they perceive as threatening.

Further study had 43 dogs tested with their reaction to both right and left tail wagging from other dogs and from a video. The overall response was that they reacted favorably to the right tail wag and became unsettled and displayed signs of stress with a left tail wag and responded in kind.

This presented proof that dogs clearly convey emotion to us and to other dogs by watching their body language which includes the direction of their wagging tail.