Final answer:
The phenomenon of memories fading over time is known as transience or storage decay. An everyday example is forgetting the details of a book read in the past, while hyperthymesia represents an exceptional case of detailed memory retention. Even significant flashbulb memories can become less accurate as time passes.
Step-by-step explanation:
The question you've asked about the memories of the Receiver from ten years before relates to transience, which is a term used to describe how memories can fade over time. This is a natural process known as storage decay. An example of this is when Nathan's mother could not fully remember the plot of To Kill a Mockingbird despite having read it in high school. As time passes without these memories being used or recalled, they tend to fade. This is a common experience many people have with books they read long ago, events they experienced, or even learning information for school. In contrast, few individuals exhibit hyperthymesia; an extraordinary ability to remember events from their past, including details from before their tenth birthday. However, even with flashbulb memories, which are vivid memories of significant events, accuracy can decline as time goes by, illustrated by the inaccuracies in President George W. Bush's recollections of how he heard about the 9/11 attacks.