A new study claims to prove that men and women have very different personalities. However, the research may not be watertight.
The study, published in PLoS One by Marco Del Giudice, Tom Booth, and Paul Irwing, looked at a sample of over 10,000 Americans who had taken a standard personality questionnaire called the 16PF. This questionnaire looks at 15 aspects of personality, such as warmth, emotional stability, and dominance. The authors found that women tended to score higher in sensitivity, warmth, and apprehension, while men scored higher in dominance, vigilance, rule-consciousness, and emotional stability. Then they went a step further, combining all their results into a measure of what they call "global sex difference," which they say is "extremely large." Study coauthor Paul Irwing tells MSNBC, "Psychologically, men and women are almost a different species."
But other scientists raise a number of objections. Dr. Janet Shibley Hyde, a psychology professor whose research has shown that men and women are more similar than they are different, points out that the study's reliance on self-assessment of personality may be problematic: "It's not very manly to say that you're sensitive." Giudice et al anticipate that criticism, however, and claim it's not a problem. They write,
We consider this objection to be weak for two main reasons. First, meta-analytic evidence shows that sex differences in aggression (a highly sex-typed behavior) are very similar when assessed by observation and self-reports, and even stronger when measured by peer-reports. Second, self-reports will actually deflate sex differences if people tend to rate their own personality in relation to members of their own sex instead of "people in general." Indeed, if people used the mean of their own sex as a reference point, any absolute mean difference between the sexes would simply disappear from self-reported scores.
Even if you accept that people automatically control for gender stereotyping by comparing themselves only to people of the same gender (a pretty big leap), the study has some other potential problems. Hyde questions the validity of the whole concept of a "global sex difference," saying that value is "really uninterpretable, it doesn't mean anything." Indeed, it's not clear that scoring people on a bunch of traits, then combining the differences in these scores, is a valid way of measuring how different people actually are. The study authors seem to ascribe to a theory of personality in which individual characteristics can be combined into one sort of Grand Unified Trait:
Personality traits can be organized in a hierarchical structure, from the broad and inclusive (e.g., extraversion) to the narrow and specific (e.g., gregariousness or excitement seeking). Researchers often focus on the Big Five, i.e., the broad "domains" of the five-factor model of personality [...]. Up in the hierarchy, correlations between broad traits give rise to two "metatraits", often labeled stability and plasticity. It may be even possible to identify a single, general factor of personality (the GFP or "Big One") at the top of the hierarchy.
But can personality really be boiled down to a single factor that can be compared and contrasted? Is it really possible to numerically measure how much men and women, as a whole, are different? This is a lot less straightforward than measuring how much men and women differ in certain specific traits or behaviors, and it's by no means a foregone conclusion that combining all the specific traits that personality psychologists have thought to measure will yield a reliable picture of the whole. Giudice et al's study is already getting a lot of attention, and its title, "The Distance Between Mars and Venus: Measuring Global Sex Differences in Personality," suggests that it's tailor-made for the popular press. Many will probably claim it proves once and for all that men and women are inherently different, and those who ascribe to this view will probably be citing it for a long time to come. When they do, remember to take it with a grain of salt.
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