Daniel Schacter writes a brief essay in the Jan. 4 issue of Nature Magazine on why our memory is not a literal reproduction of the past, but is instead constructed by pulling together pieces of information from different sources.
"One clue comes from studies indicating that memory errors can reveal the operation of adaptive rather than defective processes. For example, consider the following words: tired, bed, awake, rest, dream, night, blanket, doze, slumber, snore, pillow, peace, yawn and drowsy. When asked whether 'blanket'; was on the list (a few minutes after seeing the words), most people correctly recognize that it was; when asked about 'point';, they correctly remember that it was not. When asked about 'sleep';, most people confidently remember having seen it — but they are wrong. They falsely recognize 'sleep'; because they remember that many associated words were present, and mistakenly rely on their accurate memory for the general theme of the list."
"Future events are not exact replicas of past events, and a memory system that simply stored rote records would not be well-suited to simulating future events. A system built according to constructive principles may be a better tool for the job: it can draw on the elements and gist of the past, and extract, recombine and reassemble them into imaginary events that never occurred in that exact form. Such a system will occasionally produce memory errors, but it also provides considerable flexibility."
"Taken together, neurological and neuroimaging studies suggest that false-recognition errors reflect the healthy operation of adaptive, constructive processes supporting the ability to remember what actually happened in the past. Many researchers believe that remembering the gist of what happened is an economical way of storing the most important aspects of our experiences without cluttering memory with trivial details. We agree. But we also see another important function for constructive memory, one that emerges from an idea that a growing number of researchers are embracing — that memory is important for the future as well as the past."