Researchers reveal sex differences in the brain's form and function.

Recent studies highlight a long-held suspicion about the brains of males and females. They're not the same. So how does the brain of a female look and function differently from a male's brain, and what accounts for these differences?

Disparities Start Early in Life

Scientists now know that sex hormones begin to exert their influence during development of the fetus. A recent study by Israeli researchers that examined male and female brains found distinct differences in the developing fetus at just 26 weeks of pregnancy. The disparities could be seen when using an ultrasound scanner. The corpus callosum -- the bridge of nerve tissue that connects the right and left sides of the brain -- had a thicker measurement in female fetuses than in male fetuses.

Estrogen and testosterone influence brain development, although the process of the way in which hormones and the brain interact to influence behavior is very complex. Louann Brizendine, MD, author of The Female Brain, points out that gender differences start before birth: female brains are flushed in utero with estrogen hormones, while male brains are washed with testosterone. Females begin studying faces as babies, which shapes their brain development. Research demonstrates that the skills of baby girls in making eye contact and facial gazing increases over 400% in the first three months of life, while facial gazing skills in boys doesn't. In one study, year-old girls looked at their mothers faces 10 to 20 times more than boys checking for signs of approval or disapproval. While the boys, driven by testosterone, moved around the room to investigate their environment and rarely glanced at their mothers.

During puberty, estrogen, progesterone, and testosterone continue influencing development. Teenage girls, flooded with estrogen, get stressed around relationships and ease their fear by banning together and being socially connected. Yes, they can be mean and use their language skills - passive aggressive rumor spreading - to undermine rivals in their competition for the boys (from an evolutionary perspective sexual competition is part of the survival mechanism). But they can apologize and re-bond when necessary. Testosterone flooding the brain of teenage teen boys has the opposite effect: the teenage boy wants to be left alone. He's not interested in conversation because testosterone decreases his desire to socialize except in pursuit of sex or sports. Teenage boys at this time get stressed around challenges to their independence and authority and seek to be respected and find their place in the male pecking order through competition and conflict. They don't look for connection in same way as girls do. These are brain-based behavioral patterns that continue to influence men and women throughout adulthood.

Observations of adult brains show that this area may remain stronger in females. "Females seem to have language functioning in both sides of the brain," says Martha Bridge Denckla, PhD, a research scientist at Kennedy Krieger Institute.

Consider these recent findings. Researchers, using brain imaging technology that captures blood flow to "working" parts of the brain, analyzed how men and women process language. All subjects listened to a novel. When males listened, only the left hemisphere of their brains was activated. The brains of female subjects, however, showed activity on both the left and right hemispheres.

This activity across both hemispheres of the brain may result in the strong language skills typically displayed by females. "If there's more area dedicated to a set of skills, it follows that the skills will be more refined," says David Geary, PhD, professor of psychological sciences at the University of Missouri.

As a whole, girls outperform boys in the use of language and fine motor skills until puberty, notes Denckla. Boys also fall prey to learning disabilities more frequently than girls. "Clinics see a preponderance of boys with dyslexia," Denckla tells WebMD. ADHD also strikes more boys than girls. The symptoms displayed by girls and boys with ADHD differ, too. Girls with ADHD usually exhibit inattention, while affected boys are prone to lack of impulse control. But not all differences favor girls.

Boys generally demonstrate superiority over female peers in areas of the brain involved in math and geometry. These areas of the brain mature about four years earlier in boys than in girls, according to a recent study that measured brain development in more than 500 children. Researchers concluded that when it comes to math, the brain of a 12-year-old girl resembles that of an 8-year-old boy. Conversely, the same researchers found that areas of the brain involved in language and fine motor skills (such as handwriting) mature about six years earlier in girls than in boys.

So, do these sex differences even out over time?

Disparities Start Early in Life continued...

Females and males maintain unique brain characteristics throughout life. Male brains, for instance, are about 10% larger than female brains. But bigger doesn't necessarily mean smarter.

Disparities in how certain brain substances are distributed may be more revealing. Notably, male brains contain about 6.5 times more gray matter -- sometimes called 'thinking matter" -- than women. Female brains have more than 9.5 times as much white matter, the stuff that connects various parts of the brain, than male brains. That's not all. "The frontal area of the cortex and the temporal area of the cortex are more precisely organized in women, and are bigger in volume," Geary tells WebMD. This difference in form may explain a lasting functional advantage that females seem to have over males: dominant language skills.

How Males and Females Use Mental Skills

Geary suggests that women use language skills to their advantage. "Females use language more when they compete. They gossip, manipulate information," he says. Geary suggests that this behavior, referred to as relational aggression, may have given females a survival advantage long ago. "If the ability to use language to organize relationships was of benefit during evolutionary history, and used more frequently by women, we would expect language differences to become exaggerated," he tells WebMD. Women also use language to build relationships, theorizes Geary. "Women pause more, allow the other friend to speak more, offer facilitative gestures," he says.

When it comes to performing activities that require spatial skills, like navigating directions, men generally do better. "Women use the cerebral cortex for solving problems that require navigational skills. Men use an entirely different area, mainly the left hippocampus -- a nucleus deep inside the brain that's not activated in the women's brains during navigational tasks," Geary tells WebMD. The hippocampus, he explains, automatically codes where you are in space. As a result, Geary says: "Women are more likely to rely on landmark cues: they might suggest you turn at the 7-11 and make a right at the church, whereas men are more likely to navigate via depth reckoning -- go east, then west, etc."

While the brain allows us to think, it also drives our emotions. It may not come as a surprise, then, that the ability to identify and control emotions varies between sexes.

"Women are faster and more accurate at identifying emotions," says Ruben Gur, PhD, a neurologist at the University of Pennsylvania. Studies have shown women to be more adept than men at encoding facial differences and determining changing vocal intonations.

Women, as a whole, may also be better than men at controlling their emotions. Gur and colleagues at the University of Pennsylvania recently discovered that sections of the brain used to control aggression and anger responses are larger in women than in men.

Brain Structure vs. Environment

There may be subtle differences in how even the most equality-minded among us treat baby girls versus baby boys. Girls may be dressed in pink and given dolls, while boys wear blue jumpers and push around trucks. To some people, these environmental factors are impossible to ignore when considering the human brain. If there are differences in people's brains, it might be due to how society has shaped a person, with neurons and synapses pruned away as the brain deemed them unnecessary.

Sandra Witelson, the psychologist mentioned on the previous page, disagrees with that environmental assessment, and she uses an unlikely source to support her belief that our brains are structured at birth: Albert Einstein. Witelson had the opportunity to study pieces of Einstein's brain, and she found its unique structure to be a sort of confirmation that some brain differences simply can't be explained away with social or environmental reasons [source: Hotz]. She didn't look at Einstein's intelligence or accomplishments, but she simply observed that he had a unique brain structure that was likely already formed at birth.

This may help to explain why we don't have many Einsteins running around. And when it comes to the stereotype of women underperforming at Einstein's favored subjects of physics and math, that may just come down to slight differences in the brain as well. It may be that girls' and boys' brains develop at different rates. Our educational system, however, doesn't take that into account. When a child encounters a subject that his or her brain is not ready to tackle yet, the child may become frustrated and give up too quickly 

Knowing about the differences in male and female brains could open up tremendous opportunity in diagnosing and treatingbrain disorders.

For example, depression and chronic anxiety are diagnosed far more often in women; this may have to do with differences in the chemical composition of the brain, as one study has shown that women produce only about half as much serotonin (a neurotransmitter linked to depression) as men and have fewer transporters to recycle it [source: Karolinska Institutet]. Or, it may have to do with how the various sides of the female brain respond to emotions and pain. Men, on the other hand, are more likely to be diagnosed with autism,Tourette's syndrome, dyslexia and schizophrenia, to name a few [source: Hoag]. Additionally, disorders like schizophrenia and Alzheimer's disease can show up differently in men and women [source: Society for Women's Health Research]. Based on the location of neurons, brain injuries may affect men and women differently [source: Carey].

This sort of knowledge could affect drug treatments, or at least explain why some drugs work differently in men and women.

Let’s Talk About It

Research shows that when men and women listen to a passage being read aloud from a novel, only the left hemisphere in the male brains was activated. In contrast, women demonstrated activity in both the left and right hemispheres. The female brain is more attuned to words and sounds. Girls tend to learn to speak earlier than boys and this may be why. It could also explain why women excel at learning languages.

Take a Risk

Most men may not have a gift for language, but they do have something that many women do not, a brain wired for risk-taking. In fact, most women’s brains simply don’t reward them for taking big risks. Men, on the other hand, get a burst of endorphins, a chemical when gives a sensation of pleasure, when confronted with a risky or challenging situation. In fact, the bigger the reward the more likely a man is to take a risk.

Are We Lost?

So all of this explains why men never ask for directions right? It sort of does, actually. A man’s brain tends to give him a talent for spatial reasoning. He may navigate based on abstract concepts such as distance and direction. He may not articulate it well, but he is pretty sure where he is going. A woman on the other hand will depend on her language skills, navigating by talking about landmarks that she can see or hear. She notices and articulates if the car has passed the same diner three times. So maybe if they both work together, they will have a much better chance of never getting lost.

We may all be wired differently depending on our gender, but there is no doubt that each of us is an individual. We are a product both of our specific strengths and weaknesses as well as of our background and culture. Our differences may seem incredibly frustrating at times, but they can also be used to our advantage. There is no winning the battle of the sexes, but the better we know one another, the more likely we can take the world on together.

Some researches believe brain variations between sexes are for the best. "Most of these differences are complementary. They increase the chances of males and females joining together. It helps the whole species," Gur says.

Are teenage brains really different from adult brains?

Teenage Brain Development

In adults, various parts of the brain work together to evaluate choices, make decisions and act accordingly in each situation. The teenage brain doesn't appear to work like this. For comparison's sake, think of the teenage brain as an entertainment center that hasn't been fully hooked up. There are loose wires, so that the speaker system isn't working with the DVDplayer, which in turn hasn't been formatted to work with thetelevision yet. And to top it all off, the remote control hasn't even arrived!

The brain's remote control is the prefrontal cortex, a section of the brain that weighs outcomes, forms judgments and controls impulses and emotions. This section of the brain also helps people understand one another. As such, the prefrontal cortex is a little immature in teenagers as compared to adults; it may not fully develop until your mid-20s [source: Kotulak]. And if you don't have a remote control to call the shots in the brain, using the other brain structures can become more difficult. Adult brains are also better wired to notice errors in decision-making. While adults performed tasks that required the quick response of pushing buttons, their brains sent out a signal when a hasty mistake was made. Before 80 milliseconds had passed, adult brains had noticed the blunder, but teenage brains didn't notice any slip-up An area of the teenager's brain that is fairly well-developed early on, though, is the nucleus accumbens, or the area of the brain that seeks pleasure and reward. So what does it mean to have an undeveloped prefrontal cortex in conjunction with a strong desire for reward? As it happens, this combination could explain a lot of stereotypical teenage behavior. Part of communicating with teenagers may require the insight that they're not necessarily hearing what you say. For most adults, climbing hotel balconies or skateboarding off roofs of houses sound like awful ideas. Their prefrontal cortex curbs any impulse to do so, because the possible negative outcomes outweigh any potential thrill. But teenagers may try these things because they're seeking a buzz to satisfy that reward center, while their prefrontal cortex can't register all the risks these actions entail. This behavior is evident on a much smaller scale as well; when a teenager goes to the mall to watch a movie but comes back with an iPod, then the prefrontal cortex didn't curb the impulse buy. If a teenager spends an hour on the Internet instead of focusing on homework, it's because the teenage brain doesn't register delayed gratification. Even though the teenager can vaguely register that there will be parental punishment later on, the appeal of fun now is too strong. But not being able to reign in thrill-seeking impulses can have devastating effects, particularly when alcohol, nicotine and drugs enter the picture. But the teenage years don't have to be all doom and gloom -- plasticity can also help teens pick up new skills. The teen years may be the time when potential poets start scribbling furiously in notebooks and future hoops heroes start really hitting their shots. Before the brain is fully molded is a great time to take up the guitar or learn a new language. Not that teenagers will listen if you tell them this. But just knowing that the teenage brain needs more time and experience to develop may help both parent and child survive adolescence. Not everyone believes the teenage brain is different. One psychologist claims that this argument is extremely American-focused, and other cultures don't associate adolescence with a period of extreme angst [source: Sabbagh]. This suggests that teenage torment is a social influence. In other cultures, though, teenagers spend more time with adults, so they may have more opportunities to learn how to make thoughtful decisions.

How Bilingualism Boosts Your Brain

Language shapes the way we think. Whether we're listening to a persuasive speaker, absorbed in powerful writing, or engaged in a conversation, language can introduce us to new ideas, perspectives, and opportunities.

But at a more fundamental level, language might physically alter your mind. Bilinguals, for example, have denser gray matter in their language centers than monolinguals. Bilinguals can more easily focus on two tasks at once. They think more analytically. Parts of their brain devoted to memory, reasoning, and planning are larger than those of monolinguals.

Learning a second language is like a workout for your mind. The benefits of bilingualism, from increased creativity to the delayed onset of Alzheimer's, should encourage everyone to pick up a second - or third! - language.

Let's follow the path of language through your head as you hear, comprehend, and create words and phrases, and then pinpoint how language can shape the brain and what benefits it bestows. Here is your brain on language.

Speech in the brain

While our brains make sense of words instantaneously, the process of transforming sounds into meaning and then formulating a response winds through several areas of the brain. When your ear turns sound waves into neural impulses, those impulses trigger reactions from four major regions of the brain devoted to language comprehension and production: The auditory cortex, Wernicke's area, Broca's area, and the motor cortex.

How language shapes the brain

From the moment sound waves enter your ear and become neural impulses, your brain executes this rapid-fire series of events that few of us are ever aware of, but without which we'd be unable to communicate.

For bilingual speakers, this process involves both languages -- from the first syllable they hear, their brain is working to identify the word, and the listener's brain begins identifying any words, in either language, that could fit the sounds as they arrive in sequence. Having to distinguish between two languages can be tricky in some situations, but the brain's executive functions, especially the attention and inhibition processes, are strengthened through this process, ultimately making bilingual speakers better at switching between two tasks or handling tasks that require conflict management.

How language shapes your brain depends in part on when you learn another language. For example, Broca's area differs between young language learners and older language learners. If a child grows up bilingual, the same region in Broca's area handles the processing of both languages. However, if you learn a language after adolescence, a separate area develops for the second language near the area used for your native tongue. Despite the difference in brain structure, language learners both old and young gain the benefits of speaking multiple languages.

Because the language centers in the brain are so flexible, learning a second language can develop new areas of your mind and strengthen your brain's natural ability to focus, entertain multiple possibilities, and process information.

Just as you exercise your body to keep your heart healthy and muscles strong, exercising your mind can sharpen your decision-making and improve your communication skills. So if you only speak one language or haven't spoken your second language since high school, now's the time to get learning.

Doubling down on a pair of languages rather than just one does take extra work, but it’s work young children are generally not aware they’re doing. Bilingual people of all ages are continually addressing what research psychologist Ellen Bialystok of Toronto’s York University calls the dog-chien dilemma, encountering an object, action or concept and instantaneously toggling between two different words to describe it. Such nimble decisionmaking ought to improve on-the-fly problem solving, and studies show that it does.  Sean Lynch, headmaster of the LFNY, previously worked in a multilingual school in France in which all of the students spoke French and at least one of 12 other languages, including Japanese, Russian, Italian and Spanish. As is often the case with well-endowed schools, the students, on average, outperformed their age peers academically, and it’s impossible to determine how much of that is due to native skill and how much to the fact that they simply have access to better teachers, books and other resources. Still, Lynch observed that these students seemed to show a greater facility with skills that relied on interpreting symbolic representations, such as math or music. Lynch also believes — albeit based primarily on his own observations — that multilingual kids may exhibit social empathy sooner than children who grow up speaking only one language, which makes developmental sense. The theory of mind — understanding that what’s in your head is not the same as what’s in other people’s heads — does not emerge in children until they’re about 3 years old. Prior to that, they assume that if, say, they know a secret you probably do too. There’s a kind of primal narcissism in this — a belief that their worldview is the universal one. Once they learn that’s not the case, self-centeredness falls away — at least a little — and the long process of true socialization begins. There’s nothing that accelerates the acquisition of that kind of other-awareness like the realization that even the very words you use to label the things in your world — dog, tree, banana — are not the same ones everyone uses. Preliminary imaging work suggests that the roots of this behavior may even be visible in the brain. Some studies, for example, have shown a thickening of the cortex in two brain regions — most importantly the left inferior parietal, which helps code for language and gesturing. Bialystok is not entirely sold on these studies, since she would expect the greatest differences to be in the frontal lobes, where higher functions such as planning, decisionmaking and other aspects of what’s known as executive control take place. Some of her own work has found an increase in white matter — the fatty sheathing that insulates nerves and improves their ability to communicate — in the frontal regions of bilinguals, suggesting denser signaling and complexity of functions in these areas. “Structural differences are where the new science is really unfolding,” she says. “That work will reveal a lot.” In one study, bilinguals experienced the onset of age-related dementia 4.1 years later than monolinguals, and full-blown Alzheimer’s 5.1 years later. “One school of thought says that any cognitive reserve — education, multilingualism, even playing Sudoku puzzles — strengthens the brain and helps it resist disease,” says Bialystok. “The other says that the brains of multilinguals experience the same level of disease as those of monolinguals, but they cope with it better. They function at a higher level than they would otherwise be able to function.”

In another 2013 study, this one from the University of Kentucky, bilingual and monolingual people in the 60- to 68-year-old age group underwent brain scans while performing a cognitive task that required them to switch back and forth among several different ideas. Both groups performed the task accurately, but bilinguals were faster as well as more metabolically economical in executing the cognitive mission, using less energy in the frontal cortex than the monolinguals.

The very fact that something as simple as working with puzzles or having once got a good education can improve brain function does prove that multilingualism is not the only path to staying cognitively healthy in your dotage. And plenty of monolinguals do perfectly well at acquiring empathy and social skills early in life. Still, there are roughly 6,500 spoken languages in the world. There must be a reason our brains come factory-loaded to learn more than just one.

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