Trace Decay--More than 50% of information learned is lost in the first hour.
Anyone who has scurried around searching to find a pencil while trying to retain a phone number in their head knows the fragility of the perceptual short term memory.
Experiments by Hermann Ebbinghaus showed that the greatest amount of memory loss (over 50%) occurs within one hour after learning (providing there are no variables like organization, meaning or association involved). By the end of the day we may loose a whopping 75%.
One antidote against the forgetting curve is what is called Rehearsal—repeating the information to ourselves.
This works because the memory trace, if the stimulus is not repeated, will quickly dissipate. By rehearsing, we keep the memory loop active until we either use the information (and then let it fade) or commit it to working-short term memory.