professor at stanford university. he lived and worked as barbara intel he changed his sex to mail in 1997. -- until he changed his sex to male. i am pleased to have everyone here. i begin this conversation with my colleague eric. what are we going to talk about? eric: we are going to speak about gender identity and the biology of the brain. i like this topic in particular because it shows how great science can be. as we understand the biology of our own gender identity better and become more comfortable with ourselves, we become more empathic to somebody else's gender identity. we can understand if all of a sudden at age 10 a person says, "i'm in the wrong body." we really can sympathize with them and see what is going on. this is not only an interesting topic -- it is an unbelievably timely topic. and you and i first began talking about this six months ago, it was not on the radar screen. we were ahead of our time. but now you can take up an issue of the new york times or vanity fair without having a discussion on gender identity. charlie: 17 million people watched the diane sawyer interview. >> when we begin to speak about the biological underpinnings, we want to distinguish two different concepts -- anatomical sex and gender identity. anatomical sex is somebody who parts from sexual identity and reproduction. gender identity is a more complex image. let's begin with anatomical sex. that is determined by our genes. genes are asian chromosomes -- ancient chromosomes, and we have 23 pairs of chromosomes. we get one half from our mother and the other from our father. 23 of these are called otis holmes -- mona soames -- mono somes. the difference is quite profound -- men are xy and women are xx . chromosomes are quite different from autosomes. let's begin with the y chromosome and see how that determines the sex of the m ale. there is an undifferentiated gonad that can go in either direction -- testes or ovaries. if there is a y chromosome there , that has a region called the sex determining region, that contains the gene that activates the differentiation of the undifferentiated gonad into the testes. if the y changes not there, you have the female gonad developed. those have profound consequences. let's look at the mail differentiation first. the testes develop within the first seven weeks in utero. the testes release a massive amount of testosterone comparable to the level you have during puberty. that is it -- that is responsible for giving you the male body form. as well as having actions on heavy aspects of your being. if you have x x, you have development of the ovaries. they secrete estrogen and progesterone, and it gives you the female body form changes in the brain. clearly these are extremely important changes. that is the easy part. this is the anatomical part. the more subtle and elaborate part is gender identity. that is why we have put together this group of people to talk about that. we have been with us. he is a long-term colleague at a major scientist. -- and a major scientist. he is a member of the national academy of times -- of science, and he is a transgender person. he made a decision in his 40's to undergo a bodily change. he can tell us what it was like before when he fell he was in the wrong body, and how he feels now. interestingly enough, since people knew him as a scientist before he had to change, they can describe what they debt -- what it was like interacting with him as a woman and that was a man. he is one of the pioneers in the united states of pediatric inter-chronology -- endocrinology to help people make a decision to go on whether they are in the right body. he has implemented a procedure in the united states to postpone puberty so people can think through what they want to do and make a decision in a thoughtful fashion. the reason he wants to delay puberty is once it forms, it is a more erratic procedure. we have catherine black with us again. she is interested in how sex is represented in the brain. she has found amazingly that in the male mouse, this representation of the female and in the female this representation of the mail. this is not a completely novel idea. freud suggested we are all bisexual. one aspect of sexuality matures but the other remains. there are men the female components and women male components, even an adult life. we have melissa with us, who is interested in how kids differ -- boys and girls -- in the games they play and how they interact with each other. she is interested in how hormonal levels play in to the games children get involved with. we have janet. she is interested in seeing the differences between cognitive capabilities between men and women -- in computer science mathematics, and engineering. her data party much suggests that there is fertile difference between them. as i have gotten to know her better, i think that is incorrect. i have come to the conclusion that women -- men are superior in mathematics and engineering. [laughter] i think we are in for a fantastic debate. charlie: let me begin with ben. what led up to your decision and the impact it has had on your life? ben: i think my experience is probably typical for other transgendered people. i think i was only four or five years old when i first started to have strong feelings and felt more like a boy. i felt like a boy, i played with little boys, i preferred boys toys. i remember wishing it could be in the cub scouts and boy scouts. every halloween i would dress up as an army man or football player. it all seemed normal to me. but as i got into my early teen years, i did start to feel more uncomfortable with this. i did not feel i should have breasts. i didn't feel comfortable at all wearing dresses, makeup, jewelry. it became increasingly uncomfortable when i got in the high school. i started to be teased more by kids. i had a lot of confusion about my gender, and i felt very ashamed. i never spoke with friends or family about it at all. i felt very ashamed and confused. don't forget these were the days before the internet, so there was not a lot of information about this. once i got into my 20's, i was doing well. i was doing medical training and research training. but i was increasingly uncomfortable and i started to think about suicide. i never attempted, but i felt it -- thought about it a lot. this is a picture of me back when i was barbara. i think i was 30 at that point and a bridesmaid at my little sister's wedding. i can still remember vividly the agony that i felt, the discomfort putting on that dress and wearing makeup. i still remember that. but i did complete my training and begin a job at stanford when i was 40. about two years into that, i actually developed breast cancer. i was very confused about my gender identity, but i didn't like to have breasts. when the doctor said he wanted -- needed to do it mastectomy, i said, while you are there please take off the other breast. [laughter] ben: he was quite horrified by this. since this cancer runs in my family, he did not agree to remove the other breast. i cannot tell you how therapeutic that was. i felt so relieved to have those breasts removed. that was a very different response that my mom had when she had her mastectomy. after her surgery, the doctor started talking to me about regis -- reconstructing the breasts. i was horrified. there's no way you are putting those back on me. it occurred to me that there was something different about my gender. about a year later, i was reading the "san francisco chronicle" when i read an article about the life of james green an openly female-male transgender person in the bay area. i recognized for the first time in my life that there were other people who experienced the same sort of gender confusion. i went to see a sex change pioneer at stanford, and he ran a gender clinic, after he evaluated me they told me they thought i was transgender and offer me the possibility of changing micex. -- my sex. within weeks, i decided to change sex. i had already had the upper surgery. i did not want lower surgery. all that was needed was testosterone. you can see the effects it has out on me. [laughter] ben: it's powerful. one of the most surprising things about the testosterone is that it actually became harder for me to cry. male to female's reports that it now becomes easier for them to cry, so that was perhaps surprising. i think the main experience i had was that i felt, after i changed sex, it's hard to described the intense relief i felt, it was like in a way to being lifted off my back. i have never had another suicidal thoughts. as i had been a scientist at stanford for years i was worried that changing micex would alter my career. i have to say that everybody was immediately supportive and i am fortunate to have my career continue and have lots of wonderful students. the other thing i would like to say is, i think the other surprise after changing micex was that i found that living as a man has changed the pete -- the way people react to me. i will tell you a story about an experience that happened after i changed sex. i was invited to give a seminar about my research at m.i.t.. one of my friends told me that after i gave the cinemark, one of his colleagues was talking to him about it, -- the seminar, i was told i look better than barbara. [laughter] ben: we have all lived life as both genders. i think in general, i think we would all say that society -- with a man, it is assumed he is competent until proven otherwise, but with a woman, it is considered incompetent before proved otherwise. i have devoted part of my time to try to help women in their careers. charlie: let me turn to norman. this story may be typical for someone who is questioning. what does this say about gender identity? norman: i wish we knew more charlie. we certainly know more when we see it. i want to show you a very powerful example of identical twins who, in this case, one of the male twins and we have proven that these twins are identical and born male, but one of them at age three started to say everything about being a girl. in fact, if there was any issue that came up, she turned it into an issue of gender. she did some of those things that we consider hallmarks, like preferring to wear female underwear and pajamas, etc. by the age of seven, the family decided -- with the help of the counselor -- to change her name to a female name and have the child assume a female role. here is twin sister with twin brother at the age of just about nine to 10 years of age. they were in fourth grade. what i want to find out is if i switch all the attachments to them -- the earrings, the clothing, the hairstyles, the shoes, you could basically switch one for the other. kids with their clothes on our virtually interchangeable pre-puberty. there -- their home on levels are basically interchangeable. -- hormonal levels are interchangeable. here they are at age 14. because it is so difficult to live in a gender different from her biological sex when you have the toxic effect of your genetically or madrid and puberty -- hormone-derision puberty, that would make twin sister look exactly like twin brother. you can see that she still looks almost like a nine or 10-year-old and there is a good reason for it -- she has had her puberty suppressed. this next slide shows the level of human hormones across lifespan. the blue line's mail -- the blue line is male. during fetal life, the level of testosterone in a fetus rises to the level close to the full adult range. then it falls. then there is another blip-up right after birth. a kind of second puberty. then things go dormant. in fact, if they didn't go dormant, we would have a bunch of pubertal looking fifth-graders running around because everything is suppressed. when we think about possible causes of transgender would it be possible that this would be one of the contributing factors? norman: it is certainly possible. we still don't know what that second bump is right after birth -- watch role it plays, or whether boys warm without testes show any differences as a result of that. the problem is, when we want to look at a hormone, we have to get it out and measure it. well, you can't get it out of the brain. sometimes it is of the level of hormone that is important, but the affinity of the receptor. it is very difficult to measure such things. >> it is a very fascinating biology problem to see the underpinning of transgender identity. as you point out, it is so important, because kids who are in the wrong sex -- a suicide attempt is serious. charlie: it is one of the highest. >> in the pubertal process, this whole system we awakens. -- reawakens. the system in euro comes back. cash in you back. -- the system in utero comes back. these differences produce the body of the male and female associated with purity. we have been able to block the release of the hormone from the hypothalamus to the pituitary. once you do that so far upstream, everything downstream goes down to zero. we have a record of this medication being completely successful in shutting them down until the appropriate time. also, the fact that it is completely reversible. look at how revealing this is. the twin sister of firms a female identity, and the pubertal block was for two years. two years to get pressure of cash to get counseling without the pressure of body change. take a look at what would happen to her if she had not been given this blockade -- she would look exactly like twin brother. she is in early puberty for a 14-year-old -- he is an early puberty, but so would she have been, because they are identical. she began estrogen. while at the same time having her mail hormones blocked. with that, our patients don't need breast surgery when they feminized, because it is so effective. she is now entering junior year of high school, as is her brother. she is fabulous. this past october, the dutch reported a follow-up of patients -- 55 of whom puberty was blocked. the dutch group all had surgery at 18, at which point was gender dysphoria. their total uncomfortableness with their gender disappeared. they found that the kids treated this way functioned as well as or better. the dutch gave me the protocol in 2006, and we started using it in boston children's hospital. at the time, we were the only major medical center to do so. now over 40 programs are doing it. it is now becoming the standard of care. ♪ ♪ charlie: let me turn to catherine and talk about whether this is wired. catherine: we have just heard from dan and norman -- -- ben and norman -- humans have very early and strong senses of their gender identity. in animals, as in humans, males and females display clear differences in behaviors. mostly but not exclusively related to sexual and social behaviors. for example, males and females have very distinct sexual and aggressive displays, and we have seen in the previous episode that females are usually maternal, and males are attacking the cubs. how are these differences established and maintained? the basic mechanism cannot be studied experimentally in humans, so instead my laboratory is using the mouse as a model system. mice display clear differences in gender specific behaviors. the mechanisms by which the brain is controlled in the mouse can be studied using the powerful tools of molecular neuroscience and genetics. sex typical behaviors, particularly sexual, aggressive, and parental behavior, are extremely maintained across different animal species, so the brain control of those behaviors is also very maintained across animals. in contrast, the signals that trigger these behaviors are usually extremely specific of a given species. for example, in the species of birds called the american flicker, there is only one sign that matters to trigger gender specific behavior. that is the black mustache on the male. if you remove the black mustache from the male, then the other males will attempt to copulate with the male without the mustache, because they will assume it is female. similarly, if you paint the mustache on the female, the males will attack that mustache. if i have a mustache, i may mail -- i am a male, if i don't, i am a female. we use olfactory tools called pheromones, and humans are particularly sensitive to visual and auditory cues, a fact that has been exploited successfully by the pornography industry. once we know the signals that trigger gender specific behavior, now we can look into the brain. how is the brain processing the signals and establishing these gender specific behaviors? as we have heard, young males have a very important release of testosterone, and this release has been shown to be absolutely essential to masculinize the brain. in contrast, females do not have release of testosterone, so in males, the interpretation is that testosterone is essential to establish and maintain the very specific set of circuits underlying male specific behavior, and females organize their brain in a different way. to control female specific behavior. in our lab, we have performed a number of genetic experiments that have shown that the situation is a little bit more complex. the experiment we did is actually very simple. we look at mutants four -- for pheromone detection, which is indicated by this little crosshair on the structure of the brain. this is insensitive to sex -specific pheromone all -- pheromonal jews. we found something -- pheromone al cues. this is interesting -- the female is mounting the mail, which is a very male specific sexual display. the female is displaying a male-typical behavior. so now if we look at the male this male is now retrieving an infant and bringing it to a nest that this male had been to beforehand. as you can see, this male is displaying a female specific behavior. what have we learned from this? what we learn is that the brain of male and females contains different behavior circuits. in animals, the mail behavior circuit is suppressed by the terminal system. the female specific circuit is normally repressed. but in the minute that we observed, what is happening is the repression of the opposite sex behavior circuit -- it no longer exists, and therefore the female is now able to display male specific behavior and female specific behavior. specifically, the male is able to display female specific behavior and male specific behavior. >> it really i think provides a way we can begin exploring a transgender identity, if we have the circuits -- you can see how slight tilts for more region to another can contribute to wanting to be another gender. >> i think this is profound. >> what this shows us is that the brain of males and females are largely similar. a specific armento -- hormonal and gender regulation leads to the prominent, but not exclusive display of behavior of a given sex. animals occasionally need to display the behavior of another sex. males are occasionally able to display parental behavior, and in many species, female are displaying male behavior as a sign of dominance. the brain has actually been shown to be bisexual and fish many years ago and reptiles recently -- and now in my stash -- in mice -- so this is totally relevant to gender identity in humans. charlie: let's turn to melissa. melissa;: i study the role of testosterone in human gender development. we study genetic conditions that cause people to have either higher or level lowers of testosterone -- higher or lower levels of testosterone. it is suggested that testosterone in humans also influences gender development including gender identity. to start, it is useful to put this into context. to expand our understanding of the dimensions of gender related behavior. we have talked about anatomical sex and gender identity but also people have sexual orientation. this is separate to gender identity. this refers to our erotic interests in males and females or in some people neither. finally there is a third class of behavior called gender role behaviors. these are the other characteristics that differ on average for males and females. among these, some are bigger than others. some of the biggest are seen in childhood toy and activity preferences. the next image shows the sex difference in height. we are all familiar with this -- males have to be taller than females, but there is overlap. the males are the blue distribution and the females are the orange distribution. they overlap. the next image shows gender differences in play are similar in size to the sex difference in height. and finally, we see the gender difference in identifying with the male gender. we can see that this gender difference is even bigger. and there is almost no overlap between males and females. but there are some people who are in the other distribution. these include the people who want to change their gender. how does this come to be? we have talked about these sex differences in testosterone some of which occur very early in life. this corresponds to a. of very rapid brain development -- a period of rapid brain development. the next image shows data about women who had very high levels of testosterone before birth. about 2% of women who have low testosterone before birth and adulthood decide to live as men. you might say that's not very many -- only 2%, but that is still far more than those who were not exposed. the next image shows men in this case x y individuals, who were actually ask females, because their cells -- xy females. because their cells can't respond, they look like girls at birth and are raised as girls. and that adulthood, 99 first -- 99.9% want to live as women. >> what we already know in the vast majority of cases is what causes a desire to change sex, but here we find one concrete biological explanation for mx -- a cause mechanism. this is clearly a biological factor. probably with time will be able to identify a significant number of other ones. melissa: yes, and also, going back to the toys children like to play with, when i began this work, people thought the different interests between girls and boys were socially determined, but it turns out these are also altered by testosterone exposure. the next slide shows the toy choices in boys and girls in general versus those exposed to prenatal testosterone. boys spent most of their time playing with vehicles, shown by blue, and girls play with dolls, shown by orange. those exposed to prenatal testosterone are in between. these are different common sense of gender identity -- the influence of gender identity affects childhood play. it could be there are social factors. but finally, this is not just testosterone acting on the brain before birth, but also children who have had high levels of testosterone engaged in different behaviors. this has a feedback effect on their brain development. this becomes an increasing mechanism, where their behavior is increasingly masculinized as they go through life. charlie: thank you. janet, talk about cognitive performance and ability. janet: in our culture, we have lots of stereotypes in gender differences and abilities. people believe that boys and men are better at math, and girls and women are better at verbal skills and boys are better at spatial performance. those are the stereotypes. what is the real data show? once again, we are looking at distributions for male and female performance -- blue for males and orange for females. what you see is that the most recent data shows actually that girls are tied with boys in mathematical performance. many find this surprising, but i have data from millions of people showing this. in regards to verbal performance, you can see that there is a female advantage, but it is tiny. you can hardly see it. these are very subtle, slight differences. for spatial performance, the difference is a little larger, favoring males. i will show you one particular kind of spatial performance which involves the ability to rotate three dimensional objects in your mind and think about how they might look. other kinds of spatial performance don't show this large a gender difference. you need this kind of spatial ability if you want to be an engineer or an architect, or if you want to use matt -- a map to navigate new york city. it is important for some things, but not everything. we get this gender difference from spatial performance in the absence of a special curriculum in the schools. -- spatial curriculum in the schools. as we teach kids math skills we don't teach them spatial skills. these are completely trainable. some school districts are getting the message and are starting to institute these programs. if we want to foster something like getting women into areas like engineering, where they are very underrepresented him a instituting special curriculum might do a lot to help. i also want to emphasize the importance of cultural context. this is the percentage of phd's awarded to women in the u.s. by decade, beginning in the 1890's. it turns out -- i didn't know this -- it turns out that even in the 1890's, 11% of the phd's in math were going to women. you can see it inches up a little bit into the 1930's, and in the percentage plummets in the 1950's. only 5% of the phd's are going to women. it has been inching up ever since, so that actually today 31% of phd's in mathematics are going to women. why did it plummet in the 1950's? those are the 1950's, right? men came home from the war, women were delighted, they moved to the suburbs and had lots of babies. there is not a single biological force that causes women to be good enough to be a phd in math -- it has more to do with culture. it is findings like these that i've shown you from verbal and math performances that i've let me to propose what i call the principle of gender similarities, which is that males and females are quite similar on most psychological variables. you saw it for math and verbal performance, which are stereotypes to show gender differences. of course this has applications for women in science, technology, engineering, and math careers. this graph shows essentially what the gender similarities hypothesis is. again, we have the overlapping distributions for males and females. females are shown in orange and males in blue. you can see this huge overlap areas -- this huge overlap or males and females are similar. let me go to psychological disorders, because for some we get lopsided gender ratios. on the left part of this graph, you can see two disorders were many more men than women are affected. those are our call is a man autism. the blue r is a preponderance of males. that is not to say we don't have our call -- female alcoholics or girls with autism, but it is mostly males. on the right, we can see depression and anorexia. here we have a preponderance of women shown in orange. we do have these lopsided gender ratios. we wonder why. i am most familiar on gender differences in depression. we can see the difference is not present in childhood, but it begins to emerge between 13 and 15 years of age, as you can see the orange bar is going up there. and then it widens between 15 and 18 years of age. gender differences in depression emerge in adolescence. it is a two to one ratio -- we are going to crack this question -- we need to understand why the gender difference emerges in adolescence. it could be genes -- we have a few that have been identified that have to do with depression it could be pubertal hormones it may have to do with other factors, such as the media's emphasis on the hyper skinny models. and as girls go through puberty, their bodies get farther away from skinny models. boys have advantage because they are having -- adding muscle and that is how the models look, so that may be a factor. we also know there is sexual harassment in schools, and that may also contribute to this gender difference. ♪ sçkw?c?coó charlie: we are back to this idea of how society is responding. we know from vanity fair and time magazine -- the biggest selling time magazine cover story that year, with the exception of the pope. ben: it is unfortunate that society often considers transsexuality to be a mental illness or in a moral choice. -- and immoral choice. because of this, transsexual people are often denied human rights and are subject to violence. in many states transgender people can get fired just for being transgender. as we have heard today on this program, the brain has innate circuits that determine gender identity. being transgender is not a choice that i made, but it is how i was born. i should mention something i haven't brought out yet, that there is a broad spectrum of transgender people -- some of them may not identify as male or female, but some of us have the innate need to change sex. 40% of us attempt suicide. charlie: what should parents do? >> i think the first thing parents ought to do is sit down and take a deep breath. [laughter] norman: ok? and realize that the prepubertal child is in a state of exploration. there is no accident that both boys and girls go to the boy toys or the girl toys in kindergarten. this is not gender identity and expression, by and large -- this is almost always a gender role-play which is normal for children. of children who are fairly persistent in their cross gender play, but are prepubertal only about 20% will go on to be transgender. 80% are not going to be transgender. what i would say to parents is that if your child is getting closer to be pretty, or worse, is already in puberty, and they're showing the skin of behavior, particularly underwear wearing and saying i am the wrong gender, buying breasts -- binding breasts, etc., that you need to get help for that child past. -- you need to get help for that child fast. because a child who holds onto the belief that they are in the wrong body feels like pinocchio becoming a donkey. they may very well take their life. charlie: over the series, you and i found a range of things that we traced to the brain and understood that what was taking place within the brain was large and in some cases small -- where do you put this in terms of understanding what is going on? >> we are in the very early stages. number one, there is a biology. but our understanding is very modest. we talked about this before -- many times charlie and the -- charlie and me ask how long it will take before we can improve this in the brain. we have made a lot of progress, but we are a long way in understanding the brain. >> gender identity is so essential to who we are. i think we have a duty to provide some type of explanation. it is important to understand that it is not all black and white. ben: we have to remember that differences are not disorders. i am proud to be transgender. the real question is why does society persist in insisting that male brains are better brains? as we have heard tonight, that is definitely not the case. >> one thing that will be interesting to see is, as you function in a way you are comfortable with has increased your creativity? bemnn: i think it released a lot of mental energy that was devoted to confusion and feeling suicidal. i would say yes, i have felt so much happier and productive. charlie: 40% of people undergo anatomical change. -- norman: 40% of people undergo anatomical change. insurance companies are waking up to the idea that this is a medical condition, that it is entitled to be billable for surgical and medical aspects of their care. it will change everything because up until now people had to save all that up to have the surgery. it starts from the top down. first you have to not make it a mental illness, you have to define it as a physical problem, which it is but what freed up seeing gay people as not having a sidetrack it -- having a psychiatric illness? it was removing it from the diagnosis of social and mental illnesses. charlie: thank you to be very much for coming. -- thank each of you very much for coming. there is an interest in this and also in the conversation that is taking place. when this subject was introduced in terms of a television program, i remember someone came up to me and identified themselves as transgender. but they said that the fact it is getting so much attention made all the difference in their life. they felt not so isolated and not so different. they felt like they had been identified -- they had an appreciation of where they stood and what their options were. so what are we doing next time? >> we will continue to discuss child development. what are the consequences of growing up under difficult circumstances? how does it affect the cognitive development of children? and as it passed on from generation to generation? we will learn a lot more next time. charlie: thank you. thank all of you. we will see you next time. ♪ ♪ announcer: "brilliant ideas," powered by hyundai motors. ♪ narrator: the contemporary art world is vibrant and booming as never before. it's a 21st century phenomenon, a global industry in its own right. "brilliant ideas" looks at the artists at the heart of this they have a unique power to astonish, provoke, and shock. to push boundaries, ask new questions, and see the world afresh. in this episode, mariko mori. ♪