The Zeigarnik effect (first codified by Russian psychologist Bluma Ziegarnik in 1927) refers to the human tendency to remember an uncompleted task better than a completed one. This is presumably because an uncompleted task offers less
closure and makes less sense. Therefore, our brains keep it in working memory, hoping to clarify it. Something that we've completed no longer poses an active challenge and/or threat, so we can safely file it away in memory without extensive
rehearsal. For me this brings to mind similar effects that have been found for
traumatic experiences: when a person is unable to tell a story about their suffering, it
preys on their mind, causing a wide variety of physical and psychological symptoms (
PTSD, with its associated
flashbacks, may be an extreme form of this). As I learned well during my work with Jamie
Pennebaker, the best way to dispel this continuing stress is to work at developing a
coherent story about your experiences, which helps get them out of your head.
Although widely discussed throughout psychology and worth knowing about for this reason, there is some modern evidence that the Zeigarnik effect may not be real. However, the trauma research I have described here is extensively
replicated and
generalized, and does appear to be reliable.