Because dogs don't have episodic memory like humans, they don't think of time in concrete terms -- but that doesn't mean they don't remember at all. Your dog's memory allows him to learn things without remembering why he knows them. For example, if your dog is attacked and hurt by another dog, he won't necessarily remember the event later, but he may experience fear when he sees another dog of that breed. He may not remember his last trip to the vet's office, but the scents and sounds of the waiting room will trigger emotions.