Dogs will flick their tongue as an appeasement signal but also as a signal they're relaxing. While similar each signal has subtle differences. I will do posts on both. The tongue flick Did you know your dog's tongue can reveal how hot they are? @passionatelypets shares four tongue shapes to watch for during warmer weather: Cool & Comfortable: When a dog is relaxed Dog Teeth Chattering: Causes and What To Do PetMD Its a trick question, Chattering, when a dogs jaw vibrates and their teeth make a clicking or clacking sound, is a physiological response known as arousal. But heres the key: dog chattering Spotting Discomfort In Your DogFrom Tongue To Tail McConnell Publishing Inc.