It turns out that the act of summoning the past to the surface actually changes the memory itself. Although we’ve long imagined our memories as a stable form of information, a data file writ into the circuits of the brain, that persistence is an illusion. In reality, our recollections are always being altered, the details of the past warped by our present feelings and knowledge. The more you remember an event, the less reliable that memory becomes. And this returns us to the problem of eyewitness testimony. Eyewitnesses are repeatedly asked to recall what they saw, but their answers are inevitably influenced by the questions being asked. The result is more confidence in increasingly less accurate testimony.
Jonah Lehrer on Memory, Witnesses and Crime | Head Case - WSJ.com