Even though forgetting is such a common occurrence, scientists have not reached a consensus as to how it happens.
One theory is that information simply decays from our memory - we forget things because too much time has passed. Another idea states is that forgetfulness occurs when we confuse an item with other items that we have previously encountered (also known as temporal confusability).
Psychologists Nash Unsworth from the University of Georgia, Richard P. Heitz from Vanderbilt University and Nathan A. Parks from the Georgia Institute of Technology investigated the two theories to pinpoint the main cause of forgetfulness over the short term. In their study, the participants were presented with a "Ready" screen (on a computer) for either 1.5 seconds or 60 seconds. Following this, they were presented with a string of three letters and were instructed to remember them for a later test. But, before they were asked to recall the three letters, the volunteers were told to count backwards for various amounts of time (4, 8, 12 or 16 seconds).
The results, reported in Psychological Science, a journal of the Association for Psychological Science, reveal that temporal confusability, and not decay, is important for forgetting over the short term. The volunteers who had to count backwards for the longest amount of time were better able to recall the letters than volunteers who were asked to count backwards for a shorter time period. If decay was the culprit behind forgetting, the group that was asked to count backwards for a longer amount of time would have performed the worst during recall.
The authors conclude that "it is possible to alleviate and even reverse the classic pattern of forgetting by making information distinct, so that it stands out relative to its background". These findings have very important implications not just for everyday memory use, but also for educational practices and for populations with memory problems, such as the elderly.