We often remember things by relying on the overall gist of an event—for example, instead of storing every detail about our last birthday, we tend to remember abstract things like “I had a fun party” or “I was in a grumpy mood because I felt old.”  This strategy allows us to remember more things about an event, but there’s one major drawback: by storing memories based on gist, we actually change how we remember the event.  This happens because we are biased to remember things that are consistent with our overall summary of the event.  So if we remember the birthday party was “super fun” overall, we’ll exaggerate how we remember the details—the average chocolate cake is now “insanely good”, and the 10 friends who were there becomes a “huge crowd.”  One of the factors that could contribute to this distortion is time; as you forget the details of an event, there’s more room for gist to change how you remember things.  But you would remember the details of an event immediately afterward, right?

The article describes an experiment that suggests that this kind of classification-induced distortion occurs even for short-term memory.

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