Final answer:
Source amnesia, defined as misattributing a memory to an incorrect source, is distinct from both retrograde amnesia, which affects past memories, and anterograde amnesia, which prevents the formation of new memories.
Step-by-step explanation:
The condition that occurs when a memory derived from one source is misattributed to another source is called source amnesia. This type of memory error is a form of misattribution, which is distinct from the amnesias described by other choices such as retrograde amnesia and anterograde amnesia. Retrograde amnesia refers to the loss of memory for events that occurred prior to a trauma, where individuals cannot recall past memories. On the other hand, anterograde amnesia is the inability to form new memories after the onset of a trauma, where the formation of new episodic or semantic memories is impaired, although procedural memories can still form. Misattribution, as seen in the Hobbit movie example, is about misremembering the source of a memory, such as recalling events with the wrong person.