Decay Theory
Decay theory proposes that memories fade over time if they are not used. However, this theory is difficult to test because time always passes, and other factors like interference may also be at play.
Example: Forgetting a Phone Number
You look up a phone number, dial it, and then forget it minutes later. This seems like decay, but it could also be due to interference from other numbers you have dialed or from new information entering short-term memory.
Limitation
Decay is hard to isolate because time and interference are confounded. Modern research often views decay as a minor factor compared to interference.