Forgetting due to Trace Decay

Trace decay theory, also called the disuse theory, is the earliest theory put forward to explain forgetting. It assumes that learning produces physical changes in the central nervous system — modifications in the brain referred to as memory traces. According to this theory, when a memory trace is not used for a long stretch of time, it simply fades away on its own and becomes unavailable, much as an unused path in a forest gradually disappears.

This theory has been shown to be inadequate on several grounds. If forgetting genuinely happened because unused memory traces decay with the mere passage of time, then people who go to sleep shortly after memorising something should show more forgetting than people who remain awake over the same interval, since sleep offers no opportunity to put the memory traces to further use. The actual experimental results show precisely the opposite: people who remain awake after memorising material (the waking condition) show greater forgetting than people who sleep during the same interval (the sleeping condition). Since sheer disuse over time cannot explain why staying awake causes more forgetting than sleeping, trace decay was judged an inadequate account of f …