Experts differ on the nature of a dog's memory. Some experts maintain that dogs lack a sense of self, so they lack the capacity for episodic memory. Other researchers believe that dogs are capable of this type of memory for at least a short period of time.
Episodic memory is the ability to recall events from the past. A prime example that indicates that dogs lack the ability for episodic memory is when an owner walks into a room after being away from the dog for a short period of time, and the owner is greeted as if he had been absent for an extended period of time. The owner can leave and re-enter the room a few minutes later and receive the very same type of greeting from the dog.