Male Versus Female Intelligence: Does Gender Matter?
“In the special case of science and engineering, there are issues of intrinsic aptitude [between the sexes].”
With these words in January 2005, Harvard University President Lawrence Summers lent new fuel to the contentious debate over whether gender predicts differing aptitude or intelligence in specific areas. But while the politics of gender-based differences rage, the science moves quietly forward to discover the influences on many areas of human health and function, including the study of intelligence, aptitude, and skill.
Differences in Brain Biology
While few people would seriously argue that one sex is more intelligent, researchers have found that the brains of men and women do differ physically.
- Brain size: Men have larger brains than women by about 8%-10%.
- Corpus callosum size: Many researchers believe that a woman's brain has a larger corpus callosum, which is the pathway connecting the right and left cerebral hemispheres. Some researchers claim this larger size enables women to process information more quickly than men between the two sides of the brain.
- Cortical thickness and density: Women’s brains possess more folding. Some researchers speculate this is why women’s brains are smaller overall.
A study involving 48 men and women of comparable intelligence (as measured by intelligence testing) found that women had nine times more white matter in areas of the brain associated with intelligence than men did, while men had six times more gray matter in these areas. Gray matter is involved in the brain’s information-processing centers, while white matter is in the business of transferring information between parts of the brain.
Not only does the type of brain tissue appear to differ between the sexes, but its location differs as well. The study found that women had about 85% of their IQ-related brain matter—both white and gray—located in the brain's frontal lobes. Comparatively, nearly all of the IQ-related gray matter in men is found equally between the frontal lobes and the parietal lobes (located behind the frontal lobe).
But since the men and women achieved similar IQ test results, researchers concluded that the different types of brain architecture lead to comparable intellectual performance. In short, men and women take different paths to reach the same intellectual threshold.
Although, researchers also point out that there is some evidence that the volume of the brain's gray matter can increase with learning. So, intelligence may be influenced by other factors aside from biology.
Sex hormones, such as testosterone and estrogen, appear to have a role in brain development and function. Researchers have some evidence that sex hormones alter the development of certain brain structures during puberty. These effects persist into adulthood. For example, if a fetus is exposed to testosterone early in development, the right hemisphere develops more intensively. Hence, the reason why men are sometimes referred to as "right-brained."
Researchers have also found that cognitive abilities in one individual can change along with hormonal fluctuations. This has been documented throughout the menstrual cycle for a woman, and even daily and seasonally in men as testosterone levels change. And the gender differences in the brain may be hard-wired from the beginning in our genes.
IQ and SAT Scores
Many studies consistently show that the average IQ scores of men and women are equivalent. Although most of the common tests, such as the Wechsler Adult Intelligence Scale (WAIS), are intentionally designed to weed out a sex bias, some gender-specific findings persist.
- Men tend to perform better on spatial questions.
- Women outpace men on reading and other verbal skills.
Men score more at the extremes of IQ scoring—both high and low. More men than women test at the lower end of the IQ scale, and also at the very top. This is consistent with the membership of American Mensa, a society whose members test in the top 2% of the population on a standard IQ test. The group reports that 65% of its general membership is male, and 35% female. Yet the Association for Women in Mathematics claims that women earn half of all undergraduate mathematics degrees and one-third of PhD degrees in math.
On the college SAT test, men consistently outscore women by an average of 35 points on the math portion. Interestingly, some studies show that boys and girls test about the same in math in elementary school. The girls fall behind only later in life, so that by the time senior year in high school arrives, the boys test higher on the SAT. Researchers continue to study whether these findings—and those like it—are the result of gender differences, environmental influences, social pressures, personal beliefs and values, or a combination.
In recent years, there has been a lot of discussion regarding emotional intelligence. This is a different type of intelligence that does not deal with cognitive abilities, but rather with emotional states. The term has been popularized by Daniel Goleman’s book, Emotional Intelligence–Why It Can Matter More Than IQ?. The author states that personal skills, like self-awareness and empathy, influence your degree of success in life. Further, he argues that emotional intelligence can be taught. Moreover, it seems that gender affects emotional intelligence as well. Women tend to be more empathetic, while men seem to manage their moods better.
Brain Basics: Know Your Brain
National Institute of Neurological Disorders and Stroke
International High IQ Society
Canadian Psychological Association
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Last reviewed May 2008 by ]]>Ryan Estévez, MD, PhD, MPH]]>
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