Scientists decipher dog-tail wags
1 November 2013 Last updated at 14:27 GMT
Scientists have shed more light on how the movements of a dog's tail are linked to its mood.
Earlier research had revealed that happy dogs wag their tails more to the right (from the dog's point of view), while nervous dogs have a left-dominated swish.
But now scientists say that fellow canines can spot and respond to these subtle tail differences.
Robert Hall reports.