Tail Wagging: A dog’s tail is wagging, the dog is happy, right? Wrong. People misinterpret this signal all the time. All a wagging tail means is that the dog is emotionally aroused. It could be excitement, but it could be frustration or worse. To interpret the dog’s emotions and intentions, look at the speed and direction of the wag as well as the position of the tail. Raised Hackles: When a dog’s hackles are raised, it means the hair along their back is standing up. Technically called piloerection, the fur can fluff up across the shoulders or down the back and all the way to the tail. This is a definite sign that the dog is aroused, but not necessarily in a negative way.