Men report 2 to 4 times as many lifetime sexual partners as women report. Someone's wrong. The numbers should be equal: Every new sexual partner for a heterosexual man is also a new sexual partner for the heterosexual woman involved. The typical explanation is that both men and women are misrepresenting their sexual history. Men supposedly inflate and women underreport their sexual partners for social reasons. This misrepresentation explanation feels correct. The misrepresentation explanation is, however, wrong.
The strategy people use to answer the sexual partners question may explain why men and women provide different numbers. Underlying the whole problem is a seemingly simple question: How do we determine how frequently something has happened? Although judging frequency may appear simple, Norman Brown has found that people use different strategies when asked about event frequency. Sometimes people use an enumeration strategy - that is, they try to remember and count each instance. Other times people make rough estimates, or reasonable guesses, about event frequency.
People use enumeration and estimation strategies based on the activity they are trying to remember. People tend to use enumeration strategies for less frequent activities. How many cars have you owned in your life? I can count those on one hand: Cougar, Trooper, Jetta, Passat, and 350Z (finally a way cool ride). People use rough estimates when they think there have been many instances of the activity. How many different cars have you driven in your life? Lots, for me. Then I have to attach a number to the vague idea of lots: Around 50, I guess.
Here's the first cool part: The strategy used influences the answer given. When people enumerate, they underestimate. Brown has suggested that people forget some instances and stop searching memory before they exhaust the category (oops, I forgot to list that I owned a Chevette for a few years - not such a cool ride). In contrast, when people give rough estimates, they tend to overestimate.
So what does this have to do with how many sexual partners men and women report? Brown and his colleague Sinclair applied this line of work to reports of sexual partners. Like other researchers, they found that men reported about twice the number of sexual partners as women. No news here, but this is still mathematically impossible. Crucially, Brown and Sinclair also asked people how they arrived at their answers. Now things get really interesting. Women tended to use the enumeration strategy - listing every guy and counting. This strategy results in underreporting (whoops, forgot about that Chevette). Men, on the other hand, were more likely to use rough estimates. Using rough estimates results in over-reporting as people convert vague terms (lots) into numbers (oh, around 50, I guess).
Brown and Sinclair then made the critical test - are their differences between men and women when they use the same strategy? Their answer? No. When men and women both used enumeration, they gave similar, low answers. When men and women used rough estimates, they gave similar, but higher, responses.
In answering surveys, men and women may not intentionally provide incorrect answers concerning their sexual partners. Instead, men and women vary in their strategies for generating their responses. The strategy used determines the nature of the error.
Of course, this leads to the important next question. Why do women use the enumeration strategy whereas men make rough estimates? Brown and Sinclair offered some conjectures mostly based on women having better memories of sexual encounters and relationships. Better memory would lead to the use of the enumeration strategy. Clarity on why men and women use different strategies awaits new research.