Final answer:
Forgetting is often due to memory traces fading over time, known as storage decay, which was first described by Hermann Ebbinghaus and is also highlighted by Daniel Schacter's concept of transience, the tendency for memories to deteriorate with time.
Step-by-step explanation:
According to Hermann Ebbinghaus, forgetting occurs because presumed memory traces are thought to fade away with time and disuse, a process known as storage decay. Ebbinghaus's research on memorization using nonsense syllables to create his famous forgetting curve demonstrated that the retrieval of information declines rapidly over time if the information is not used or rehearsed. Part of the difficulty with remembering details about a previously read book, like the plot of To Kill a Mockingbird mentioned in the example, can be attributed to this principle. In addition, psychologist Daniel Schacter references this idea in his categorization of the 'seven sins of memory,' among which the first is transience, indicating that memories weaken over time.