So how are the male and female brains different?

You might think that the differences between the way that the sexes think is largely a result of upbringing—the fact that little girls get Barbie dolls for their birthdays and have pretend tea parties, for example, while boys play with G.I. Joes and fantasize about blowing up stuff. But a 2002 study by UCLA and Texas A&M psychologists suggests that such choices may be innate, because our distant evolutionary cousin, the vervet monkey, Cercopithecus aethiops sabaeus, does pretty much the same thing. In the study, young male velvets preferred playing with cars and balls—the type of toys that you might expect a boy to gravitate towards—while girl monkeys went for dolls and toy cooking pots, objects

that have a traditionally female association. (Both boy and girl monkeys, though, liked picture books and stuffed dogs about the same.) “The results suggest that sexually differentiated object preferences arose early in human evolution, prior to the emergence of a distinct hominid lineage,” the researchers concluded.

If vervet monkeys could read, they’d probably want to check out the 1990s bestseller Men Are From Mars, Women Are From Venus, in which relationship counselor John Gray argued that the two human genders think so differently that they might as well be two separate alien species from distant planets, each with its own language and customs. The E.T. metaphor might have been a bit over the top, but when it came to his underlying message, Gray wasn’t just hyperbolizing. Neuroscientists have discovered that while we’re all thoroughly human, our brains aren’t all the same. Men and women have significant differences in their brains,

which tend to make us differ measurably in problem-solving abilities and behavioral tendencies with someone of the other sex. A number of scientists have theorized that our ancient forefathers and foremothers probably evolved this way, because the two genders had to play contrasting but complimentary roles in our species’ survival. In our modern society, where men and women do the same jobs and increasingly share the same child-raising and homemaking

responsibilities, some of those brain differences may have outlived their usefulness, and may even complicate our lives in ways that we find exasperating.

Male and female brains actually start diverging in the womb. Ultrasound images of fetuses at 26 weeks, for example, have shown that females already have a better developed corpus callosum, the bridge of nerve tissue that connects the right and left sides of the brain. That difference seems to persist into adulthood, and helps give women the ability to use more of their brain to process language than men do. In a research study, when men and women listened to a passage being read aloud from a novel, only the left hemisphere in the male brains was activated. Women subjects, in contrast, showed activity in both the left and right hemispheres. That may explain why girls speak earlier than boys, and tend to out-perform boys in school when it comes to learning languages, and why women tend to be better at expressing themselves

verbally. "If there's more area dedicated to a set of skills, it follows that the skills will be more refined," University of Missouri psychologist David Geary explained in an article on the WebMD website.

But don’t feel too bad for men. They’re equipped with brain features that give them the edge over women in other areas, such as spatial reasoning, navigating in unfamiliar

environments and taking risks. Plus, they have bragging rights in another area: Their brains are just bigger than women’s. At birth, a male baby has a brain that’s typically 12 to 20 percent bigger than the little girl in the next bassinet, and some of that size difference persists into adulthood.

Here are some key brain differences between the sexes.

Gray and white matter: A man typically has six times as much gray matter, the type that’s involved in information processing, as a woman does, while she probably has 10 times the amount of white matter, the stuff that facilitates connections between different parts of the brain.

Different-sized parts: The female brain has a bigger frontal cortex, which is involved in activities such as language, judgment, planning and impulse control, than men do. A woman also has a larger limbic cortex, the area

responsible for emotional intelligence. But men have a decided edge in another area. The hypothalamus, the region of the brain involved in mating behavior, is about 2.2 times larger in a man than it is in a woman. And the male brain has an edge in the parietal lobe, the part that helps with spatial orientation—that is, making mental maps of where places and objects are located, and how the relationship to them changes as you move.

Visual processing: Female brains are hard-wired to see more fine degrees of color on the red-orange spectrum than men. They also have superior ability to remember faces, because there are more receptors for the female hormone estrogen in the hippocampus. Men, in contrast, have visual cortexes that are more strongly activated by blue light.

Brain chemistry: When men are confronted with a risky or challenging situation, their pituitary gland have a greater

tendency to pump out large quantities of endorphins, a brain chemical that creates a sensation of pleasure.

As a result of the variations in their brains, men and women tend to approach tasks and problems differently, and each gender tends to be better or worse at some activities than the other. Women’s mental equipment can recall lists of words or paragraphs of text from memory better than men, while men’s

brains tend to be better at tasks that require them to judge distances between objects or mentally rotate an image in order to solve a problem.

But to make things even more complicated, the differences in male and female brains sometimes cause them to use different methods for performing the same task—getting from one place to another while driving, for example. With their spatially-advantaged brains, men tend to navigate using abstract concepts such as north and south or distances. Women, capitalizing on their greater ability to work with language, navigate by talking about landmarks and things that can be seen or heard.

Differences in brain chemistry may also explain why men are inclined to take greater risks if there is a chance of a bigger reward. In studies where both genders are offered a small but guaranteed increase in annual pay, versus an opportunity

to get a large increase by being the top performer in the company, women overwhelmingly choose the first option, while most men are willing to risk getting no raise at all in exchange for a shot at getting a lot of money.

Many scientists theorize an evolutionary explanation behind these differences. Back when humans were hunter-gatherers, gender differences may have worked to the

advantage of the species. In many early societies, men were the risk-takers, the advance scouts who wandered farther afield in search of food. Women, who took care of the children, stayed closer to the camp, where they could rely upon familiar landmarks. While that limited their chance to find food, they may have compensated for that by being better able to identify nutritious fruit and vegetables with their superior ability to differentiate colors.

Those brain differences still exist as vestiges of an earlier, more difficult time in human existence. And while they’re not as useful today, we can’t just pretend that they don’t exist. "There is no unisex brain," as University of California-San Francisco neuropsychiatrist Louann Brizendine has written. "Girls arrive already wired as girls, and boys arrive already wired as boys. Their brains are different by the time they're born, and their brains are what drive their impulses, values and their very reality."