Very interesting article by Cognitive psychologist Gordon H. Bower of Stanford University who looks at: Why is it hard to "unlearn" an incorrect fact?
Building on the correct information can help you learn new associations to it: add something to change how you retrieve the item from your memory. You might replace your question “Name of John’s wife?” with “Name of John’s second wife?”; or use an elaboration that contains the accurate information, such as “We are weird” or “My niece is nice”; or convert 7 X 9 into 7 X (10 – 1) = 70 – 7 = 63. As you practice the elaborated association, the simpler direct association (7 X 9 = 63) eventually replaces the earlier one, which weakens without rehearsals. Labeling and rehearsing the wrong association (for example, saying to yourself, “7 X 9 is not 63”), however, are distinctly counterproductive.