Final answer:
The Decay theory assumes that memories fade over time due to a lack of use or rehearsal, leading to forgetting. This theory contrasts with the concept of interference, which also contributes to forgetting but involves competition between new and old information rather than a simple passage of time.
Step-by-step explanation:
The assumption that time plays an important role in forgetting pertains to the Decay theory. This theory posits that memory traces fade away or deteriorate over time when there is no attempt to retain them. Research by Peterson and Peterson (1959) concluded that without active maintenance, short-term memories tend to fade as time elapses. However, forgetting can also occur due to interference, as studies have shown that both proactive and retroactive interference can disrupt memory retrieval. For example, Keppel and Underwood (1962) found that proactive interference contributed to the forgetting of newly learned information in short-term memory tasks.
Memories in the long-term memory, unlike short-term memory, require consolidation over hours to weeks and are believed to have unlimited capacity. But even long-term memories can be susceptible to interference, decay, and retrieval failures. For instance, a failure to retrieve a memory may be due to interference, as illustrated when recently learned information hinders the recall of older information (retroactive interference) or older information inhibits the learning of new information (proactive interference).
In conclusion, it is the Decay theory that primarily addresses the role of time in forgetting, suggesting memory traces become less available over time without use or rehearsal.