Final answer:
Memory decay is the reduction in the ability to retrieve rarely used information over time, distinct from interference, which is the impairment of memory due to other information.
Step-by-step explanation:
The reduction in ability to retrieve rarely used information over time is called decay. The term refers to the theory that memory traces weaken over time when they are not used, leading to the inability to retrieve information from long-term memory. The concept of memory decay is different from interference, although they are both reasons why forgetting occurs. Interference is split into two types: proactive interference and retroactive interference. Proactive interference describes when older information hampers the recall of newly learned information while retroactive interference occurs when newly learned information affects the recall of older data.