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Sex on the Brain: A Conversation with Biological Psychologist Marc Breedlove

Timothy Beneke

Eastwood Bay Press, September 22, 2000.

In the fall of 1999, Cal psychologist Marc Breedlove and his team of researchers set up booths at a Bay Area street fair offering lottery tickets to anyone who would, (1) Allow their hands to be photographed on a Xerox machine, and, (2) Fill out an anonymous questionnaire that asked, among other things, the participant's age, sexual orientation and number of older brothers. Breedlove was operating from some intriguing hypotheses. On average, among men, the ring finger is significantly longer than the index finger, especially on the right hand, an apparent effect of the release of testosterone, a "masculine" hormone, in the womb. In women, the two fingers are, on average, almost the same in length. Building on previous research that suggested that lesbians are exposed to greater testosterone in the womb than straight women, Breedlove wanted to see if lesbians had index-to-ring-finger size ratios that were more like men's, which would count as further evidence that they had been exposed to more testosterone in the womb than straight women.

And that was precisely what he found. Results of the experiment, published in the leading science journal "Nature" were widely publicized, and although for a few days newspaper readers were busy looking at their fingers, Breedlove has made it clear that, due to considerable overlap between lesbians and straights, finger length measurements can in no way be used to identify gayness in women.

Breedlove also confirmed another intriguing fact: men who have more than one older brother are significantly more likely to be gay than men with no older brothers. Not only have researchers established that the more older brothers a man has, the more likely he is to be gay, but those rare men who have ten older brothers have a 50-50 chance of being gay. Researchers have struggled to explain this. Breedlove found that the more older brothers men have, the smaller are their index fingers in relation to their ring fingers, which suggests that they received higher than average amounts of prenatal testosterone.

Breedlove's research is part of a move toward greater biological understanding of the roots of human behavior that has blossomed in the last thirty years. Increasingly, certain forms of mental illness like schizophrenia, manic depression, and obsessive compulsiveness are understood less and less as a result of family trauma and more and more in terms of a poorly - or differently -- functioning brain. And proudly held personality traits look more and more to be strongly influenced by genes, as behavioral geneticists inform us that identical twins raised apart are far more alike than fraternal twins raised together. Today, middle aged psychology professors who once dismissed as reactionary the idea that intelligence is strongly influenced by genes now take such ideas for granted.

Many feminists, eager to liberate biological sex from the straightjacket of gender, so we all need no longer feel compelled to act or feel what our culture defines as "masculine" or "feminine" at any given time, have been reluctant to acknowledge any biological basis for gender difference. They point to the undeniably myriad ways cultures create gender differences, and argue that gender differences in behavior are a social construction. From the day they are born, men and women are treated differently, and learn to act differently.

More recently, ambiguous evidence that sexual orientation has biological roots has come to the fore, causing a mix of reactions from gays and lesbians. Some gay men and women simply do not wish to have their sexuality explained. Others, especially gay men, feel strongly that they were just born gay, and welcome biological evidence that supports this intuition. Some fear that biological explanations will be used against them; others hope that society will be more accepting of gays if they learn that they are "just born that way."

What seems clear is that our state of knowledge about the biology of gender differences and sexual orientation is in its infancy, and little can be said with great confidence. In recent years, two mystifications have clouded the public debate on the biological bases of gender and sexual orientation. First, polemicists insinuate that the truth of any scientific claim is somehow connected to the motives of researchers, or the political uses to which research findings may be put. Writers on gender, (this writer included) have in the past dismissed scientific claims and theories, not on their own terms, but because they are afraid of the uses to which they will be put. But the motives for research, and the potential political uses of research tell us nothing about the validity of research.

And second, when neuroanatomical differences between men and women (or gays and straights) are uncovered, the public is quick to believe that biology is the primary cause of difference in gender or sexuality. This fails to understand the neuroplasticity of the brain - the idea that human experience and behavior itself can alter the brain. It could be that the socially mediated different experiences and behaviors of men and women (or gays and straights) cause their brains to be different. Neuroplasticity, the notion that experience itself changes the brain, has yet to be integrated into most public discussions of these issues.

So what, from a scientific standpoint, can we confidently say about genetic and biological influences on the differences between men and women, gays and straights and, for that matter, the transgendered? To address these issues, I met with Marc Breedlove, a professor of biological psychology in the Cal Psychology Department and a leading researcher in these areas. Breedlove received his Ph.D. from UCLA in 1982 in physiological psychology and soon began teaching at Cal. He is the recipient of many awards for his research, the author of 80 scientific articles, and co-author of two textbooks.

At 46, Breedlove is a friendly, unassuming man who comes across as unusually thoughtful in his attempts to interpret scientific findings about gender and sexual orientation. We met for the interview at his office in the Cal Psychology Department.

Timothy Beneke: Since we're going to talk about the origins of sexual orientation, I want to start with a political point. My own view is that all sexuality is worth understanding and explaining. But clearly, it would be homophobic to view "homosexuality" as something "abnormal" or "deviant" and in need of explanation, and heterosexuality as the norm that does not need explaining.

Marc Breedlove: I agree completely. And in fact, we are equally trying to explain both. Gays and lesbians have historically been persecuted and are still persecuted, and we try to be very sensitive to that. If you ask most heterosexuals when they first had sexual feelings toward the opposite sex, and if they remember when they decided to have those feelings, they will tell you that they never made such a choice, it just turned out that way. And if you ask them if it had to do with how they were raised, or how they were formed in utero, most heterosexuals would find nothing threatening about the idea that something that happened in the womb could set off a chain of events that led to them at around 10 years of age to have these funny sexual feelings about the opposite sex. Heterosexuals are in the majority and they have not been persecuted as gays and lesbians have been, so they don't find these ideas threatening. Gays and lesbians are still persecuted, and have good reason to ask questions about the purpose of research about the origins of sexual orientation.

Beneke: So tell us why you did this research comparing ring fingers with index fingers among gays and straights.

Breedlove: I normally do experiments on animals, specifically rats and mice, and in all the cases I know of so far in mammals, we can make an animal's brain and behavior as masculine or feminine as we want, and we do that by manipulating testosterone. If I give the right amount of testosterone at the right time in life, I can make the animal's behavior as masculine as I like. Across a wide range of animal species, the story is that the more masculine the structure of the brain, the more masculine the behavior. And we can make the brain more masculine by administering masculine hormones. This holds true for mice, rats, hamsters, dogs, and monkeys where this has been done. Hormones do not account for all behaviors, but they are very important in sex differences among animals.

So what do I mean by masculine behavior? It can be many things. With human sexuality there is an overwhelming concern about the characteristics of the partner. That is very hard to get at when you work with a species that can't talk. So it is difficult to know about that. You can ask what odors rats find arousing and whether rats either prefer to mount or be mounted, but they don't care that much who their partner is. We also look at things like spatial learning ability; others look at things like preferences for sweets. And for all the differences where researchers find sex differences, testosterone has been able to account for almost all the differences. To give an example, in rhesus monkeys males yawn more than females. They yawn as a social signal to let others know not to mess with them, and that is completely explained by testosterone in adult males. If you take the testosterone away from males, they yawn less; if you give testosterone to females they yawn more.

Beneke: Could this behavior in monkeys be socially mediated? Could it be that the added testosterone affects social status, and the enhanced social status causes the female monkeys to yawn more?

Breedlove: Yes, it could be that the testosterone's effect is mediated by some social factor, or it could be a direct biological effect of the brain. But every sexual difference in behavior we see in mammals, when people ask if testosterone is responsible, it has turned out to be true.

Beneke: That is a remarkable fact.

Breedlove: Yes, natural selection in general does not usually cause a particular principle to be that widespread. The question I have is whether this relates to humans at all. To my mind it is still very much an open question. The question for humans is: do men and women behave differently because society trains them, or do these hormones that masculinize animal brains have similar effects on humans as well? In my heart of hearts I can't help but think that both factors are at work. But it has been remarkably difficult to show that hormones are having any effect on human behavior, because human behavior is so complicated. A frustration of my professional life is that I believe that there is a genetic and hormonal influence on gender differences between men and women, but I can't really prove it. It's not that humans are just like animals, but that just like in animals, hormones play an important role. It is obviously a smaller role in humans, and not nearly as powerful.

And even if hormones are having an influence on human behavior we know that cultural influences are going to be modulating that. Culture could easily modulate the effects of hormones so much that you could no longer trace its origins. So the application to humans is always in the back of my mind in doing research in animals.

And we have to keep in mind the ways testosterone could influence behavior. It could cause a person to look or behave in a certain way, which causes the culture to treat them differently, which causes a person to have different experiences, and to behave differently, which in turn alters the brain and causes more different behaviors in an endless spiral. If you have two people who are given different environments that elicit different behaviors, their brains will be different. This is called neuroplasticity, and the public at large has yet to grasp it. So whenever we find a brain difference between two groups of people, we have to ask if the brain difference caused them to be different, or if they were treated differently and behaved differently, which caused their brains to be different.

In fact, that is what happens with some gender differences in a very obvious sense. Extra testosterone is released in the womb, which causes males to develop genitals and secondary sex characteristics different from females, and when humans are born, everyone looks at the baby's genitals and establishes that they are male or female, and treats them differently. And that different treatment definitely has effects on the brain. In other words, one way that testosterone causes the brains of men to be different from the brains of women is by causing men to be born with a penis. That penis causes people to treat them differently, and having people treat them differently causes their brains to be different, so that maybe that is why they are more likely be engineers. So it is not a question of whether testosterone affects the brain at all. The question is: does testosterone affect the brain directly or only through social interactions?

No one really knows the answer. We have this mind that arose on the plains of Africa that was developed to help get food, and yet is capable of learning calculus and theorizing about the beginning of the cosmos. You put that powerful a problem solver in an organism and it starts coloring everything we do. I don't see it as impossible that we are so socially conditioned that the effects of testosterone have gotten erased altogether. But I don't really believe it.

Beneke: So tell us how all this fits in with your measures of finger lengths.

Breedlove: In May of 1999 I read an article that made a convincing case that finger lengths reflect exposure to early testosterone in the womb. They found that for men, on average, on the right hand, the ring finger is significantly longer than the index finger, and that for women, they are almost the same, with the ring finger still a little longer. And they found this difference in 2-year-old children. Everything I know about sex differences in the body suggests that any sex difference in two-year-old children is almost certainly due to the extra testosterone released in utero to the male.

So we have this hidden indicator of early testosterone exposure that appears stable across the lifespan. So there is an obvious question: Can you use this to gain any indication if early testosterone has any influence on who people are attracted to? The fact that males and females have different finger ratios doesn't help you much in terms of sexual preference because we already know that most men are exposed to more testosterone in early life than most women. So we can't use this hidden indicator to ask why heterosexuals are attracted to the opposite sex. But here we could compare straight and gay men and women.

So two undergraduates, Terrance Williams and Michelle Pepitone, and I set up a study. We looked at some undergraduates and quickly confirmed that in most men the index finger is considerably shorter than the ring finger and in women they are more likely to be the same. And we confirmed that this difference is stronger in the right hand. And we wound up giving away lottery tickets at several gay pride and other events to get people to Xerox their hands and fill out a questionnaire.

We found a consistent difference between straight and gay women in finger length ratios. It was a very strong finding -- gay women were much more likely, on the right hand, to have index-to-ring-finger ratios that were like men than straight women were. It was by no means a perfect correlation. There was substantial overlap, but the chances that what we found would happen randomly were less than one in fifty. That is a pretty strong finding. We could not find a way of explaining it away. We couldn't think of any plausible social influence causing lesbians to have this difference. Our conclusion was not that all lesbians had been exposed to more testosterone than straight women, but on average as a group, we had to conclude that some lesbians were getting more testosterone in utero.

And I want to be clear: there is no way to tell if someone is gay from this. It is a difference that shows up if you look at significant numbers of people. It's a little like height. Men on average are taller than women for biological reasons, but you could not determine a person's sex by height, because there is a lot of overlap. But if you take a sample of five men and five women at random, the mean height will be significantly higher for men. The differences in men and women in the finger ratios are more subtle than the differences for height. And the sexual orientation differences between straight and gay women is even more subtle. So you cannot use this to determine sexual orientation. On the other hand, there is a difference and it is hard to explain how these differences could have gotten there unless the lesbians on average got more exposure to testosterone.

Beneke: Can we also say that, because of the overlap in finger size ratios between gay and straight women, that testosterone cannot not totally explain the difference in sexual orientation between gay and straight women?

Breedlove: That's right, another take on our findings is that hormones cannot totally explain sexual orientation or there would have been no overlap between lesbians and straight women. With anything as complex and lovely as sexual orientation there are going to be a multitude of causes.

But we can imagine that the fact that some women got exposed to more testosterone than other women somehow starts a cascade of events to occur that draws on social influences to lead to lesbianism. What if a child early in life has behaviors that are more masculine than other girls, and what if the family picks up on that and treats them differently? This could have an influence.

Beneke: Or, it could be that in some direct way unmediated by social interaction having greater testosterone exposure in the womb causes some women to be gay.

Breedlove: Right, we don't really know. It is also possible that testosterone does something to the brain early in life and that, social influences notwithstanding, it influences the girl to become gay. But as someone who is aware of how much the brain is altered by experience and behavior, this is a less attractive hypothesis. I am sure that the sex differences we see between men and women are not in some simple way biologically determined. Culture is too strong. The way society treats boys and girls has a very strong effect. No one has found a society where boys and girls were treated the same.

Beneke: In your study, you looked at older brothers and sisters, and found some interesting things regarding gay men.

Breedlove: We did not find a difference between gay and straight men in ring-to-index-finger ratios, but we did find a more masculine ratio in men who had more than one older brother when compared to men who had no older brothers, which suggests that the more older brothers you have, the greater your testosterone exposure in the womb. This is especially interesting because there are a lot of data sets that look at men's sexual orientation and number of older brothers, and all of them show that gay men tend to have more older brothers than the rest of the population. For the rest of the population, the ratio is 106 brothers to 100 sisters, whether older or younger. In our survey, gay men had 140 older brothers for every 100 older sisters, but for younger brothers and sisters, for gays the figure is also is also 106 to 100, as with the rest of the population.

Beneke: So can we confidently say that gay men are more likely to have older brothers?

Breedlove: Yes, the research of Ray Blanchard is pretty strong on this. But keep in mind that, especially in a society that no longer has such big families, most gay men have no older brothers. And even among men with five older brothers, most are straight. This is only a statistical effect. And older sisters don't matter. But the more older brothers you have, the more likely you are to be gay. You can look at the Kinsey data, where Kinsey asked people how many siblings they had and what their ages were. As you go down each group, the more older brothers you had, the higher percentage were gay. This was something Kinsey didn't notice; you have to look at the data with this in mind.

Many gay men have no older brothers and most latter born men with older brothers are straight. And yet, for each older brother a man has, the probability that they will be gay goes up by a third. First born probability is low. You have to have about 10 older brothers to have a 50-50 chance of being gay, if you are a man.

Blanchard estimates that about 15% of the men who are gay in North America, are gay because they have older brothers. If their mother had had fewer boys before them, they would be straight today. 15% is a significant number. And think of it politically. Why on earth should people have hundreds of fewer legal rights and be unable to marry the person they fall in love with, just because their Mom had sons before them?

Beneke: So can we say with certainty that some gay men are gay because their mothers had boys before them?

Breedlove: Yes. There definitely are gay men in America today who are gay because their mothers had sons before them. The evidence is unshakable. The question is: why are they gay? Up until the time we did this study on finger lengths, the best argument was that it was due to social behavior. You grow up around all these older brothers, and who knows, they treat you mean, or they take up all the macho slots in terms of family ecosystems and the latter born try to find some avenue of expression, or some such hypothesis was presented.

But we looked at finger ratios and found that the more older brothers a man has, the more masculine is the ring-to-index-finger ratio -- in other words the smaller the index finger is in relation to the ring finger. It is hard to explain that as being socially conditioned. First, no one knew it was there. How having older brothers could cause your index finger to grow at a different rate than your ring finger, especially on your right and but not your left hand, is difficult to explain socially. It looks biological. And given that the finger ratios seem to be established before birth, it seems that there is something different in the prenatal development of latter born men that results in the difference in finger ratios we saw. And they are also more likely to be gay.

It is possible that these two facts -- that later born men with older brothers have more masculine finger ratios and are more likely to be gay - have nothing to do with each other. It is possible that they are totally separate, but I doubt it. Here's why: When we look at the finger ratio we see exactly the same pattern of effects on finger ratios that other people have reported on sexual orientation. Older sisters don't matter to sexual orientation and older sisters don't matter to finger ratio. Neither brothers or sisters influence the chance that a girl will become gay. And older brothers and older sisters had no influence on the finger ratio of women.

But here's a little pebble in my shoe. When we look at the birth order effect on finger ratios across all men, it is strong. When we divide up men in terms of gay and straight; among the straight men the birth order effect is not quite significant for finger ratios, but it is close. The sample we have for straight men is still somewhat small. As we get bigger samples we will have to see what we find.

What we can't explain is why most latter born men, who on average have this unusually masculine finger ratio, are straight. We just don't know. One thing is clear: if latter born males are getting greater exposure to testosterone, then Mom has do be the conduit for this process; there is no other way for the younger males growing in the womb to know the mother has given birth to other males. It has to be Mom enabling the release of more male hormones. If the finger ratios are getting established before birth, Mom is not only imparting but also remembering; she is not doing it through social interaction before birth. We don't know how it comes about. But Mom's body has to be remembering that she has had previous males to facilitate this. What is most likely is that she is somehow changing the amount of testosterone that the male fetus puts out. She is somehow causing the testes of the fetus to put out slightly more testosterone to make it slightly more likely that he will be gay. Where is the memory? How does it work? We will try to develop an animal model to see if we can understand this.

Beneke: Let's address a paradox. We have a stereotype of gay men as being "effeminate," and in fact there is research suggesting that a significant number of gay men describe themselves as being gender atypical and having been "sissies" as children. Yet your research suggests that the more older brothers you had, the more you were exposed to testosterone in the womb, and the more likely you were to be gay, which suggests gay men are more masculine, as measured by testosterone exposure. And there is research suggesting that gay men have more circulating testosterone, larger genitalia, and other evidence of more exposure to testosterone. How should we make sense of all this?

Breedlove: I'm sure there are many influences on human sexual orientation. So I'm also sure there are many avenues to heterosexuality or to homosexuality. It seems pretty clear that little boys who want to be girls, who, as Richard Green of UCLA pointed out, are often called "sissy boys," are much more likely to be gay in adulthood than are other boys. But most gay men don't report having had those feelings, and most gay men are quite happy being males. So I think it's possible that some men are gay because they were exposed to slightly less testosterone in utero, while other men are gay because they were exposed to slightly more, while yet other men are gay for reasons that have nothing to do with testosterone. No one knows which pathway is the most common, but our findings are more compatible with the notion that gay men, on average, see the same amount of early testosterone as straight men. But the latter born men, who are more likely to be gay, seem to have seen more early testosterone, which is consistent with the reports that gay men have larger genitalia than straights. Maybe that's because there are more latter born men among the gays.

The idea that gay men might be hypermasculine is also consistent with what is perhaps the most fundamental sex difference in sexual behavior: men are more likely to be interested in, for want of a better phrase, "casual sex", than are women. On this scale, gay men seem to be masculine, not feminine.

But if some, perhaps many, gay men are in fact hypermasculine, where does this idea that gay men have feminine behavior come from? Obviously, I don't know, but I'm sure culture plays a big role in guiding gender roles among both straights and gays. It's pretty clear that human societies have always included men who were primarily attracted to other men, but it's not at all clear that those men always displayed feminine behaviors. In classical Greece at least some men whom we would describe as gay were also what we would describe as jocks. The idea that gay men would have feminine mannerisms really came to the fore in Victorian England, among the so-called "dandies".

So I think it's time to wonder whether the effeminate behavior of at least some gay men is due to social learning. If a boy realizes, at about age 10 or so, that he is having sexual feelings about other boys or men, does he then turn to our culture for guidance about what he's supposed to feel and how he's supposed to behave? If so, then popular culture strongly pushes the message that gay men talk and move in feminine ways: the hack sitcom writer who wants to introduce a gay man does so, using only 5 seconds of screen time, by having him display such behavior. This theoretical boy we're discussing may emulate such behavior, especially in environments where it is safe to do so. And of course, once such behaviors are established in gay subcultures, they become self-regenerating, as these are ways of expressing solidarity and a sense of belonging amid the larger, mostly hostile, culture.

Having spent all this time talking about how effeminate behavior in some gay men may be the product of social learning, I want to emphasize that that would not, in any way, mean that there's anything wrong with gay men, or straight men, being effeminate. In general, I think many, perhaps most, of our society's troubles would be greatly alleviated if only men behaved more like women. Think what that would do to the problems of violent crime, rape, drug abuse, and child abandonment, not to mention road rage.

Beneke: Let's talk about the different play styles of young boys and girls. We can go to any day care center and see a difference in three and four-year-old boys and girls. Boys are more likely to be engaged in rough-and-tumble play and girls are more likely to be in the corner engaged in an imaginary social drama that is softer and gentler. The physical movements they prefer appear to be very different. This appears to hold cross-culturally so far as we know. In no known cultures do very young girls engage in rough-and-tumble play while boys act more gentle.

Breedlove: The cross-cultural consistency alone does not convince me that it isn't all socially mediated. There are some aspects of culture that are universal, but that does not mean it is biologically mandated. But cross-cultural consistency does invite the hypothesis that it is hormonally driven. And the hypothesis gets strengthened when you see that there are sex differences in rough-and-tumble play in rats, mice, monkeys and other animals, and that those sex differences are caused by testosterone. For example, in rats and monkeys you can cause a female to display more rough-and-tumble play as a juvenile if early in life you expose her to masculinizing hormones.

Beneke: It is tempting to say that three-year-olds have not lived long enough and internalized enough culture for social conditioning to explain something so basic as the pleasure they take in physical movement.

Breedlove: Yes, but it could still be a function of social conditioning. You have to consider that three-year-olds are much smarter than adults in how much they learn each day. They are learning incredibly fast and they could be learning the behavior differences.

Beneke: But you can generate a line of reasoning that says: kids that age engaging in spontaneous play are going to do what is pleasurable, and what is pleasurable in terms of muscle movements will be influenced by the brain.

Breedlove: In general I like theories that talk about the peripheral origins of a hormone influencing the brain. I like the idea that a hormone influences the brain so the body is different, and that a person using their body learns about differences and pursues a different line of activity than they would otherwise. And this has to leave an imprint on the brain.

But consider another possibility. Take two children who start out in every atom identically the same and give one the opportunity to undergo rough-and-tumble-play and deprive the other of that opportunity, and that will have to influence their brains. Bradley Cooke and I have done that experiment with rats. We put newly weaned rats either with two other males to play with, or put them in a cage by themselves, and let them grow up into adulthood. When we looked at the region of the brain that controls rough-and-tumble play, in adulthood, the animal in a cage by itself had a smaller brain region than the animal in a cage with two males.

Beneke: So it could be that parents treat kids differently and encourage rough-and-tumble-play in boys and discourage it in girls, and that explains the difference?

Breedlove: Right. There are three points. First, what the parents do matters. And one of the things parents do in influencing their children's play is that they are influencing the structure of their child's brain. That is not only not controversial, but is inescapable. Second, it is also possible that testosterone acts on the body and causes the individual to behave differently, and that causes the brain to develop differently. A third possibility is that testosterone goes directly to the brain and also changes things there, in a way that is unmediated by behavior. Maybe the reason boys love rough-and-tumble play is not because their muscles and bones are different, but because their brains are different.

All three could be true. It also appears that gender atypical children are more likely to arise in families that are not doing the gender policing quite as thoroughly. But we don't know enough to explain it through environmental factors.

Beneke: Let's talk about the famous "John Doe" case that provided a kind of horrible experiment about gender. Thirty five years ago, at the age of 8 months, two identical twin boys were circumcised, and in the process, one had his penis burned off by accident. The boy was sent to psychiatrist John Money at Johns Hopkins who decided to perform sex reassignment surgery and remake the boy's genitals as a girl's, give him hormones, and have his parents raise him as a girl.

"John Doe" was studied over the years, and something remarkable was reported that gave feminists heart. It was claimed that the boy adjusted fine as a girl and there were no problems. Feminists interpreted this as evidence that gender really is socially constructed and that biology was trivial. It gave reason to believe that there was no biological mandate at work forcing us into gendered straightjackets. You could just cut off an infant boy's testicles and penis and give him hormones, raise him as a girl, and it would work out fine. So therefore, the rest of us are free to be what we choose to be in terms of gender.

A recent book by John Colapinto informs us that in fact, what was done turned out to be a psychological debacle. The boy, now an adult, says that he never felt like a girl, and at adolescence, threw off his girl's clothes and insisted he was a boy. He feels deeply traumatized by the process.

Breedlove: Yes, in 1973, I was taking my very first psychology course and the very case you just mentioned was presented to us. He was supposed to have adjusted as a happy little girl. Had that been true, it would indeed have been a pretty powerful presentation.

William Reiner at Johns Hopkins is now studying a group of children who were born as boys with malformed genitalia and surgically reassigned as girls and raised as girls. The early evidence is not encouraging. As these sexually reassigned girls get older, one by one they say, "You know what? I'm not a girl. I'm a boy."

Beneke: It is beginning to look like you cannot just remove a boy's testicles early in life and give them hormones and treat them like a girl and expect it to work. There appears to be something in the brain that causes these kids to insist that they are boys.

Breedlove: First, my frustration with the John Doe case is that I think the media has swung in the opposite direction to making excessive claims about the importance of biology. All we really know about the case is that Money was wrong. The accident happened when "John Doe" was 8 months of age; the sex reassignment happened in stages. It is not at all clear how parents who have been treating a boy as a boy, suddenly start treating him like a girl. It is consistent with the idea that biology causes gender difference, but it is a lousy test case, book sales notwithstanding.

Beneke: What if pretty much all of the kids being studied now at Johns Hopkins turn out to insist they are boys at adolescence?

Breedlove: Reiner seems to be saying that a large number of them are saying that they are really boys. The problem is that they are having surgery on their genitalia and elsewhere. Their genitalia don't look like everyone else's. And this may create some problem as the kids see their genitalia being altered and forming. The problem is that we are getting reports on what is happening but Reiner has not written a scientific article about this, so we don't really know what is happening. It does count as some kind of evidence that testosterone early in life does something to the human brain to make people feel and act masculine. And normally it is boys who get this testosterone. But until we see the results published it is hard to draw definite conclusions.

Beneke: Let's talk about transsexuals, people who feel passionately that they were born in the wrong body. There is research that a part of the brain, the bed nucleus of the stria terinalis, central portion, or BSTc, is larger in men than in women. Dutch researchers found that in male-to-female transsexuals, the BSTc was of the size normally found in women. What can we make of this?

Breedlove: We don't really know what the BSTc does in humans, but it is fair to say that it is getting information about hormones, and it could well be playing a role in sexual behavior and involved in olfactory functions. But we don't really know what it does in any species. The Dutch researchers accomplished a lot in finding this. But they only studied 6 transsexuals and nearly all of them had been castrated before they died; and all had received estrogen. You can't rule out the possibility that the lack of testosterone caused by the castration in adulthood contributed to the brain difference. The differences in the brain could be the result of the transsexuality and not the cause of it. The other possibility is that those people were born with smaller BSTcs and that caused them to feel like they were women stuck in men's bodies. It will be a long time before we know for sure.

It is interesting to note that the brains of male-to-female transsexuals are different. For me they have to be; otherwise they would behave the same as other men. And for the public it is good to know that it is not just that these people chose to take on some veneer, but that their transsexuality is something grounded in the brain, just as the feeling non-transsexuals have of themselves as men or women is grounded in the brain.

Beneke: Let me look at your basic philosophy. A basic assumption in your work is that if two people behave in consistently different ways, there must be something different about their brains. For you there is no mysterious gap between consciousness and the brain; consciousness is thoroughly grounded in the brain.

Breedlove: I am an avowed materialist. I don't want to hear any talk about spirits or demons or ghosts causing people to do things. And this puts me at odds with our culture.

Beneke: But people may experience demons or spirits in their consciousness, even if they are caused by the brain.

Breedlove: Yes, but those are manifestations of things going on within your brain. They are not separate entities fiddling with your brain.

Beneke: Philosophers will tell us that brain "causes" mind or consciousness, but no one seems to have a clue as to what that really means.

Breedlove: The mind is a function and process that is being carried out by a physical entity called the brain. Exactly how it works is still a mystery.

Beneke: And yet we experience ourselves as having freedom. How do your reconcile free will with your materialism?

Breedlove: There is a reason why I don't talk much about free will. I love the old idea that if I were to pick up a rock and throw it, and if the rock were to suddenly become conscious half way in its trajectory, it would think to itself, "Oh, I think I'll go over there." I think asking people why they do things is a lousy way of finding out why, even if they are being completely honest. I think that psychological research makes it clear that people often aren't aware of the influences on their behavior.

Beneke: That is a hard insight to integrate into your life.

Breedlove: It's important not to integrate that into your life. I'm completely serious about this. An organism that has no experience of free will is an organism that will sit in the corner and do nothing. And evolution has never favored such organisms. I have no idea whether I have any free will or not, and I will die not knowing. But I know it is very important for me not to think about that too much. It is very important for me to continue to enjoy this feeling I have that I'm making decisions about what I do.

Beneke: When the writer Isaac Singer was asked if he believed in free will, he said, "Do I have a choice?"

Breedlove: Exactly! So my answer is that, intellectually, I don't think there is any such thing as free will. Yet I'm at my happiest when I feel that I have a free will and I'm happy to continue with what I suspect is a delusion. I encourage everyone to do likewise. If I could package that conviction in a bottle, it would be easy to sell.

Beneke: But isn't it the case that it is the scientific study of the behavior of matter that causes us to believe that everything is determined? And it is our experience, our subjective consciousness -- something very different from matter -- that tells us we have some free will. Our consciousness is something that cannot be studied scientifically; it can't really even be observed, because if we try to observe our consciousness, the observation, in a sense, becomes our consciousness.

Breedlove: Yes, we are left with a paradox, and one I don't expect anyone to solve any time soon.

(c) 2000 Timothy Beneke