Final answer:
Douglas is recalling his autobiographical memories, a type of episodic memory, which are explicit memories of personal experiences. The correct answer is autobiographical memories.
Step-by-step explanation:
When six-year-old Douglas recounts his birthday party events, such as describing his friends, the food, and his favorite presents that occurred several weeks ago, he is recalling his autobiographical memories. These are a type of episodic memory, which is information about events we have personally experienced. This type of memory is part of explicit memory and involves recollecting specific details and the personal experience of the event at a particular time and place.