Why is it that once you learn something incorrectly (say, 7 9 = 65), it seems you never can correct your recall?                                                                                                                    J. Kruger, Cherry Hill, N.J.

Cognitive psychologist Gordon H. Bower of Stanford University answers:
IDENTIFYING, CORRECTING and averting our memory errors are part of a cognitive process called memory monitoring. Incorrect associations can be tough to change, but we can use techniques to retrain our brain.
When strong habits impede our ability to acquire a desired new habit or association, we experience a common phenomenon known as proactive interference. Wrong associations appear in common spelling errors such as wierd for weird and neice for niece. Persistent mistaken connections also can cause embarrassing errors, such as calling a mans second wife by the name of his first. Interference is stronger the more previous wives youve had to deal with, and it is more difficult to overcome the stronger the habits are.
Accurate memory monitoring requires a well-functioning prefrontal cortex (PFC). Young children, who have an immature PFC, and stroke patients with extensive PFC damage make more errors as a result of memory-monitoring failures. They are more likely to confuse the source of information they recall, and they are more susceptible to accepting as true an event they only imagined.
You can overcome proactive interference by consistent (even silent) correction, especially when you space rehearsals over time. But it takes some conscious practice. We have to identify (or be told) when we have just made an error so that we can correct it immediately. Our inability to do so is typically the cause of the errors persistence. 
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 Johns wife? with Name of Johns second wife?; or use an elaboration that contains the accurate information, such as We are weird or My niece is nice; or convert 7 9 into 7 (10 1) = 70 7 = 63. As you practice the elaborated
association, the simpler direct association (7 9 = 63) eventually replaces the earlier one, which weakens without rehearsals. Labeling and rehearsing the wrong association (for example, saying to yourself, 7 9 is not 63), however, are distinctly counterproductive.

In the art of persuasion, does a persons sex or body type make a difference?
Randy M. Zeitman, Lansdowne, Pa.

Social psychologist Rosanna E. Guadagno of the University of Alabama replies:

PEOPLE ARE MORE SWAYED by the opinions and behavior of those who are like them. Specifically, those who are akin in appearance, hobbies or behavior are relatively more persuasive to one another. For instance, a study published in 2005 in the Journal of Consumer Psychology examined the effect of name resemblance on persuasion. Half the participants received a request to participate in a survey from someone who had the same first name as theirs and a close-sounding last name, whereas half received the same request without the name similarity. Letters matched for name similarity recruited nearly twice the number of participants.

So, yes, all else being equal, a skinny man would usually believe another skinny man over a heavier man. Things are seldom equal, however; in our society, skinny people are considered to be more attractive, and attractive people are more persuasive. We witness examples of this effect every time we turn on the television and see good-looking actors endorsing products.
The impact of a persons sex is more complicated. Overall, men are slightly more swaying than women because we tend to perceive men to have higher credibility and expertise. Yet that is not the situation when the topic is stereotypically feminine (child care, for example).

Other factors are the relationship between persuader and target (whether they are friends, competitors or strangers) and their mode of communication (face to face versus e-mail, for example). My research indicates that when a woman is trying to influence another woman she doesnt know, a face-to-face conversation works better than e-mail because women typically get to know one another quickly in person. On the other hand, a man trying to plead his case with another man he knows but is not similar to is better off using e-mail, where the focus is on the text and not the persuader.

Finally, across all communication modes, people are usually more successful at winning over members of their own sex. I have found that both men and women are more likely to adopt a more positive attitude about tighter security on campus or taking a comprehensive exam (topics most college students find abhorrent) when the persuadereither a real person or computer-controlled virtual personmatches their gender.

Note: This article was originally printed with the title, "Ask the Brains."