In this study Daniel Gilbert and Timothy Wilson (2009) together with other researchers have demonstrated that when we anticipate an upcoming event as important, we are more motivated to remember and build stronger and more lasting memories of it. On the other hand if the sense of importance is only established in retrospect, the motivation that helps establish the memories is weak or missing, and we are much less likely to remember the past. This may not be too surprising, except that we largely fail to anticipate the difference between pre-event importance and post-event importance has on our ability to recall past events. Weak, fading, or non established memories are difficult or impossible to recollect no-matter how important they may have become in retrospect. Most people when judging the memory of others generally fail to anticipate this difference and therefore expect people to remember more than they may be able to.
There is enough unpredictability and randomness in our world and it seems to be save to say that we will each encounter our fair share of inability to remember information and/or past events. Sometimes we may insert false memories or self-serving biases to fill the gaps and at other times we’ll simply wish we could remember. Ironically we may notice more often those times when we just can’t recall something that now seems important, while overlooking how much more frequently we have correctly judged information to be unimportant. It is a filtering process thanks to which we are saving ourselves a lot of time and energy that can be re-directed elsewhere.
Kassam, K. S., Gilbert, D. T., Swencionis, J. K, & Wilson, T. D. (2009). Misconceptions of memory: The Scooter Libby effect. Psychological Science, 20, 551-552. [free full text PDF]