Scientists now agree with Jorge Luis Borges, who said, “Every time we remember something, after the first time, we’re not remembering the event, but the first memory of the event. Then the experience of the second memory and so on.” Through a brain process called reconsolidation, every retrieval of a given memory actually changes it. As one expert, Nelson Cowan, told me: “We edit the past in light of what we know now. But we remain utterly unaware that we’ve changed it.”