Final answer:
Memories may not be remembered earlier and only as an adult due to encoding failure, storage decay, and the seven sins of memory. Traumatic events may also lead to repressed memories that can be recalled later.
Step-by-step explanation:
There are several reasons why memories may not be remembered earlier and only as an adult. One reason is encoding failure, which happens when information is not stored in our memory in the first place. For example, we may not pay attention to the details and actively process the information, leading to the inability to remember it later. Another reason is storage decay, where unused information tends to fade with the passage of time. Memories can also be affected by forgetting, distortion, and intrusion, which are known as the seven sins of memory. Additionally, in cases of traumatic events, repressed memories can be locked away for decades and later recalled through techniques like hypnosis and guided imagery.