"Dogs attempt to deceive one another, with marginal success--when a dog is terrified, fear pheromones emanate from his anal scent glands, and it's not great if the guy you're facing off against knows you're scared. A dog can't consciously choose to be deceptive by not synthesizing and secreting those pheromones. But he can try to squelch their dissemination by putting a lid on those glands, by putting his tail between his legs--"I'm not scared, no siree," squeaked Sparky." --