Typically, I enjoy reading studies that report on comparison functions of the human brain with those of creatures on this planet. According to a study published in a recent issue of Current Biology, the way a dog wags its tail (assuming it has one) is a consequence of what is going on in their canine brain. When dogs are feeling stressed they tend to wag their tails to the left; when they are feeling good, they tend to wag their tails to the right. According to lead author, Giorgio Vallortigara of the University of Trento in Italy, tail wagging sends a message to other dogs. Dogs who see another dog wagging to the left experience anxiety and elevated heart rates, whereas dogs who see another dog tail-wagging to the right remain relaxed. Left-brain activity in dogs resulting in tail wagging to the right means they are having a positive response that invites another dog to approach. Right-brain activation suggests a negative withdrawal response. Interestingly, there has been some brain imaging conclusions about the human brain: when the person is feeling happy, the left cerebral hemisphere lights up; when the person is experiencing one of the protective emotions, the right cerebral hemisphere lights up. No tail-wagging clues for others to pick up, however . . .