Forgetting is a complex cognitive phenomenon influenced by several factors, among which interference and decay are particularly prominent. These processes explain why individuals often struggle to retrieve specific information from memory, leading to lapses in recall that can be observed in everyday situations.

Interference occurs when competing memories hinder the retrieval of particular information. It can be classified into two types: proactive and retroactive interference. Proactive interference occurs when previously learned information obstructs the recall of new information. For instance, an individual might have difficulty remembering a newly created password because their memory of the old password interferes with recalling the new one. This type of interference is particularly common when the old and new information are similar, as the similarities between them increase the likelihood of confusion.

Retroactive interference, on the other hand, occurs when newly acquired information disrupts the recall of older memories. A typical example of this is observed in language learning. A student who initially learned French but has recently begun studying Spanish might find it challenging to recall French vocabulary due to the interference caused by the newly acquired Spanish words. This process highlights how the brain's updating mechanism can sometimes compromise the retrieval of older, less frequently accessed information.

In contrast to interference, decay theory posits that memory traces, which form when new information is learned, weaken over time if not regularly activated. This weakening leads to a diminished ability to recall the information. For example, a student who memorizes a list of historical dates for an exam may find it challenging to remember them years later if the information is not periodically reviewed. Decay theory emphasizes the importance of rehearsal and reinforcement in maintaining memory over time, suggesting that the mere passage of time can erode our ability to retrieve specific memories.