Forgetting due to interference occurs when various sets of associations stored in memory compete with each other at the time of retrieval. The interference theory suggests that associations remain intact in memory but conflict during recall. It includes proactive interference where past learning interferes with recall of later learning, and retroactive interference where later learning interferes with recall of past learning.

In contrast, forgetting due to retrieval failure occurs when retrieval cues are either absent or inappropriate at the time of recall. Retrieval cues are aids that help us recover information stored in memory. According to Tulving, memory contents become inaccessible due to missing or unsuitable cues, not because of competition between associations.

Thus, interference involves competition between stored associations, while retrieval failure is about the absence of appropriate cues needed to access stored information.