Nicole Rust in Scientific American:
We’ve all felt the fog come over us when we mistake someone’s name right after being introduced, fail to remember where we left our car in the parking lot or tell a friend the same story twice. Our memory is rarely as reliable as we’d like. But at times, it also surprises us. We may somehow remember family stories told to us long ago, the names of our middle school teachers or trivia facts buried deep in back of our brain. Despite the standard glitches, our memory can retain far more than either experts or we expect. Conclusions about its reliability vary tremendously. Some studies conclude that memory is extremely accurate, whereas others conclude that it is not only faulty but utterly unreliable. Even memory experts can struggle to predict how accurate our recollections are. In a recent study at the University of Toronto, such experts were asked to predict the accuracy of memories of events that happened two days earlier. While recollections of these events were very good—more than 90 percent correct on average—the experts predicted they would be only 40 percent correct. Why is our memory so mysterious?
Studies that conclude memory is good typically test recollections of more recent events and emphasize the astounding accuracy of their details.
More here.