Fraternal twins are, by definition, dichorioinic, diamniotic (DCDA) pregnancies - that is, they have **two separate and independent fetal placental circulations**. The two don't share. What quantitative evidence is there of increased in-utero testosterone exposure in the female fetus? What quantitative evidence is there of increased estrogen exposure in the male fetus? C. M. Mullaly, MD
94
Wow, this being published is problematic. I read the actual study. It is loaded with conjecture which they try to justify with bad statistics. First, there is no discussion of baseline data on normal testosterone levels over the course of a normal singleton female pregnancy. So we have no baseline. Second, there was no testing of testosterone levels during twin pregnancies of either same sex or mixed sex pregnancies. So, no concrete data. The high end of testosterone levels in a twin same sex female pregnancy may be within the range we see in some mixed sex pregnancies. We just don't know! What about timing of hormone spikes over the course of a pregnancy? What about maternal hormone levels? What about twins in one amniotic sack vs two? This data set was trying to predict social outcomes...of pregnancies in NORWAY...from 1967-1978!! What social and societal expectations existed for mothers and girls from that time...in NORWAY. The study attempted to control for some of those effects but that is not really possible. I was born in 1965. I assure you that the environment and expectations of girls from my generation are highly different from those born in the last 20 years let alone today. In my grandmother's family all resources were poured into her brother. She got to college because an outside adult saw her potential and paid her way. This kind of disparity used to be common and would be magnified by the financial stress of a twin pregnancy. Twin girls would get even treatment
78
@kathleen twins in one amniotic sack would have to be of the same sex, so this does not apply here
11
@kathleen
Monoamniotic twins, that is, twins who share a placenta and are in one amniotic sack, are identical, therefore they are either both male, or both female.
I don't think the actual levels of testosterone need to be established for the purpose of this study. The authors just examined the numbers of twins and their educational achievement.
9
Muscle rules, so said a philosophy teacher to me years ago. Those who have muscle rule those who don't. Thus, it's a man's world. And that view is validated no matter where you look around our world today. For good or ill, muscle rules.
11
"Also, a person’s biology alone does not determine a life course. Family, environment and personality shape it, too."
There's the big disclaimer buried at the end. Nurture or Nature or Culture? How was that accounted for in the study? Doesn't look like it was. Conclusion, read into it what you will and take it with a grain of salt, especially if you're like me, the female twin, whose life and personality doesn't at all resemble the national averages of Norway's twins.
13
@Nancy
When it comes to Nature vs Nurture.
It's always both.
17
So reading these comments I find it very scary that NY Times readers who likely consider themselves to be intelligent and well educated can’t differentiate between a large scientific study and “anecdotal “ evidence. Your experience as part of a male-female twin set or knowing one or two of these sets of twins is just anecdotal evidence and doesn’t account for a whole lot. It’s no different than insisting that cigarette smoking isn’t bad for your health as your grandmother smoked and lived to 98, or that you never wear a seat belt and are still alive and well.
31
@Greenie
Actually they seem to simply be pointing to legitimate questions that were not properly asked. The idea that simply because a male twin died that this did not effect how the surviving female was raised is weird. A child who has a dead twin acting out and the most logical conclusion must be exposure in the womb to testosterone? Really?
20
I'll have to read the journal article. How could they jump to the testosterone conclusion without controlling for how the twins were raised? Seems equally or more plausible that the girls were raised with different expectations than their brothers. I know I sure was! My brother was raised with expectations that he would be the breadwinner, me with expectations that I be a great wife and mother (with a career that I could fit around those two goals). I was encouraged to do well in school, but career was not the focus. While my experience was blatant, this more subtle differential treatment is common. I'm a big believer in the importance of nature in the nature v. nurture debate, but this seems like a pretty far out conclusion from this study!
20
Oh jeesh. Sometimes research is really weird and strange and focused on the ridiculous. A boy and girl twin are fraternal which basically means they are a brother and sister born at the same time. No different than having a younger or older brother near your age. We well know siblings have great affects on each other ; in utero or not. I have a twin brother and I did better in school, graduated college, great career, 2 good husbands, many great boyfriends, 2 fabulous children. I am fit trim energetic. My twin? Lousy student, no college, fell apart in business, terrible physical shape, opioid addict.
These studies prove nothing.
9
This is interesting. Obviously humans are not cattle but in cattle, the female twin of a male calf is generally known as a "free-martin". They will be infertile and not of any commercial use as a female calf. Given this, female calves born as twins to male calves are generally not kept in a herd as probably 90% of them will be so affected. So probably not surprising that human female twins of males are impacted by this.
The only cautionary tale I can see here is that as in-vitro fertilization has upped the chances of having fraternal twins, we should probably err on the side of caution and try to only implant same sex embryos if implanting more than one in a human female.
10
Pre-natal testosterone effect seems highly conjectural and ignores gender-based upbringings. Personally, as the male half of a boy-girl twin, my sister was never a tomboy. We were both precocious for music, but she was encouraged and supported, while, as the boy, my musical interests were only tolerated and I was pushed to science. She always got higher grades but we both got graduate degrees. She eventually became a successful university music professor, I ended up in science and engineering and eventually made more money than her, but that’s the nature of our elected fields. Other than my sister’s choice not to marry or have children (her students were her kids), I see little correlation between our experience and the conclusions of this paper.
12
@Jerry Martin -- your experience is one data point. And indeed, your sister's "choice not to marry or have children" is entirely consistent with the article's findings. And the article does not ignore gender-based upbringings; in fact, it is a discussion of how biology and culture interact. The focus is on a recent large study, but it refers to many others, including animal studies, that show a clear influence of testosterone, produced by the male fetus, on the development of a female fraternal twin. It's not conjecture.
13
You are trying to use anecdotal “evidence “ to support your viewpoint. That’s no different than arguing that cigarette smoking can’t be harmful as your grandmother smoked and lived to 98! The referenced studies use large data sets; not 2 kids from one family. And btw, your sister not choosing to marry or have her own children does in fact fit the results of the study. Just sayin......
15
This article is probably oversimplified. I would like to know more about the women whose twin brothers died early, for example, in terms of their expression of typically "male" behaviors like aggression. If it was lower in these females, then exposure to testosterone in utero is only one factor affecting the achievements of these women.
Perhaps we need to know more about females whose male twin died in utero or very shortly after birth, so that socialization would play less of a factor.
6
@Barbara I agree with you on this point especially. I fall into the category of "females whose male twin died in utero or very shortly after birth". Although I was first taken by this article (who doesn't want scientific insight into the whys of their personalities and life path) I see some of its flaws upon second reading and reading of the critical comments. In the end though, even a better study of this group for comparison will never really answer the nature verses nurture debate, though a little more well researched conjecture is always interesting.
5
@Barbara
Having a twin die is not a neutral data point. It may effect the nurturing/ attitude of parents. Or it may indicate a problem in the womb unrelated to testosterone. After all, why did the twin die? Illness? Lack of nutrients? Stress? I'm unimpressed.
4
Is there no ill in the world that does not affect women disproportionately. Why not write about those, NYT, if they exist?
15
Am I the only one who thought that this article was about a woman who had “twin brothers” rather than a woman with a twin brother?
44
@Lisa
My daughter had twin brothers. She had her own twin brother, and also a set of older twin brothers.
5
@Lisa Nope. I thought the same thing because of the headline. I am a woman who has a brother who is a twin, but not my twin. Would've been clearer, if clunkier, if it had been something like "women who are half of a boy-girl twins".
9
The headline writer really threw me here:
"Women With Twin Brothers Are More Likely to Face Penalties at School and Work"
I was wondering what consequence could arise from having two brothers that are twins.
How about "Women with a male twin..."?
64
As the female half of a girl/boy set of twins my experience has been the opposite of the article - I excelled academically, have been successful in my career, married, had children and definitely skewed towards the more ‘girly’ On the traditional spectrum of gender roles. I am close friends with two other women who are also the girl half of boy/girl fraternal twins and they too share a similar experience in the Eastern U.S. - perhaps this study should investigate whether it is biology or the social experience in Norway that contributed to the results.m
18
@Robin Rabbit
Agreed. I was looking for greater evidence that testosterone was the actual differentiating factor. Perhaps it was in the study but the article didn't flesh it out.
4
There have been other studies in other countries which have had similar results (Finland is one I believe -not sure why this area of the world is interested in boy/girl twins). This does explain some things about my personality to me although none of it extreme. It may also explain my polysistic ovaries which might be related to the elevated testosterone - a friend also the same kind of twin had this condition and of course this is related to the fertility issue. My life has been perhaps more unsettled as a result but it has been a great ride so far and it came along with a great brother
9
No, scientists Do Not say that everyone lies on a spectrum of testosterone levels. There is at least a 10 fold difference in mean levels among adult men and women, higher in adolescents. It might be PC to pretend that there is a spectrum, but this article is supposed to be about science, not the social justice wars.
13
The study concludes that it must be testosterone exposure in the womb, since they saw the same results with girls whose male twin died early in life. But growing up as a girl who knows their twin brother died early is a strong environmental factor that cannot be discounted. That girl's experience is different from a girl growing up with no twin at all.
9
@nowadays — They compared those girls to girls whose female twin died early in life.
5
What a weird study to undertake. Seems to me that the more self-assured and strong a woman is, the more most people (men and women) want to take her down. I've experienced that my whole life.
15
@atb I agree. We like docile women. I have no idea what that is. I wear the pants.
3
"The study, published in PNAS, was of 728,842 people, including 13,800 twins — everyone born in Norway from 1967 to 1978 — in addition to records about their family, education and work."
Perhaps the claims of this study has more to do with Norway than with twin boys.
13
Here's a little anecdote I hope you'll enjoy: I was a member of the Abraham Lincoln High School (Brooklyn) class of 1958. Our student government president was Robert Holtzman. Vice-president (as chosen by the student body or some part thereof, never knew) was his twin sisten Elizabeth Holtzman. I don't want to paint myself as a big feminist pioneer but even then my clear understanding was that Elizabeth was the superior candidate for student government. I'll think that's all I'll say for now.
11
@Rodgerlodger -- this anecdote nicely illustrates some of the main points of the article, such as the importance of cultural bias and responses to behavior. Elizabeth Holtzman might well have been a stronger candidate than her brother, but in 1958, she nevertheless came in second to him in the student government vote. Not mentioned in this article but in related research is the fact that prenatal exposure to testosterone is associated with a higher incidence of lesbian orientation among female fraternal twins, also consistent with Elizabeth Holtzman's experience. Dealing with gay or trans identity in a less than tolerant society might contribute to behavioral issues leading to higher dropout rates, etc, referenced in the article (clearly *not* Elizabeth Holtzman's experience).
6
In cattle, the female twin of a bull calf is referred to as a freemartin. They are almost always infertile.
16
I wasn't a twin, but grew up in a rural neighborhood where all available playmates were male. I became a tomboy, athletic, adventurous, until puberty kicked in. By then, I was socially inept around girls, but got along fine with guys. Continued to do outdoorsy, loner sports in my 20 & 30's, (since most team sports didn't accept F players.)
I've done fine when self-employed, & not fine working with *women* colleagues, which has impacted my success & income considerably. Their usual complaint is I'm "demanding & rude", but no one can ever give an example of this behavior on the job when managers ask for one--it's just a feeling I apparently give women. (One colleague once yelled at me in the middle of a crowded lobby: "I hate the way you walk, and the way you talk!")
Take a look at the work of the linguist Deborah Tannen & how she differentiates play with boys in groups, vs girls in very small groups. With the girls, being different is unforgivable. If you are perceived as "thinking you are better than us"--whether you do think that--or they simply assume you do), you are toast.
If you do well in that career, they'll be certain you think you are better. You'll be ostracized from then on.
And God help you if you try to advance in a workplace dominated by women.
So my guess is it's not a slightly higher rate of testosterone handicapping these female twins, it's that they don't act quite as other women think they should act. With real world consequences.
67
There's enough unfounded supposition and implicit bias and gender assumptions in this article to make an evolutionary psychologist blush! You can do better than this NYT.
30
Knowing two sets of boy-girl twins well, I maintain that our experience is the exact opposite. The girl was the "leader" from early childhood all the way through school and beyond, the more academically successful, and more adventurous member of the tandem. And in both cases, the boy (today a man) is a gentle soul, a kind and courteous gentleman. So maybe there's a case, if anecdotal and not statistical, for the opposite of the study's conclusion: that the girl's estrogen had a calming and sweetening influence on her male twin...
15
@American Mom
American Mom, I am the daughter of a fraternal twin (with a brother) I have a twin brother, and I am the mother of fraternal twin girls. Neither my father nor my uncle went to college but were moderately successful. I went to college and my twin brother did not. And he is not "sweet". One of my twin girls went to UCLA on a scholarship and her equally bright twin sister is in school now, having taken 10 years off to be a park ranger at Yosemite. I don't know how old my grandmother was when her twin boys were born, but my mother was 37 when she had us and I was 35 when I had mine. All were natural pregnancies, I also have an older daughter and an younger son. This is one of the few instances where girl/boy twins have been studied as a group. We are usually left out. I am not sure how much I agree with the findings, but I am glad to see us being studied.
5
I went to the paper provided by the link in the article.
The primary endpoints of the study are statistically significant and support the conclusions. There are two exceptions,the point estimates are in the direction supporting the conclusions, but not the confidence intervals. It is likely due to the small numbers rather than a lack of association.
Pending validation in other datasets (Danish birth registry and Icelandic data are two datasets that come to mind) that data is highly suggestive, provides an insight to the world of human behavior and could very well be correct. It may be important information for parents, educators, and pediatricians to be aware of.
Among the dissenting comments, I found comments from two women whose experience agree with the paper's thesis.
The interpretation may be controversial, but this study has statistical merit.
11
This study, along with our experience with transgender kids, further demonstrates that male and female characteristics and preferences have a strong biological component and aren't just the result of societal expectations.
13
@J. Waddell
No it doesn't. At best it demonstrates, some component which is totally and completely different than strong.
4
It would be interesting to figure out if women born to younger mothers (when in utero testosterone levels much higher) experience similar development of masculine traits. Assuming the T-levels are comparable to women with male twins it would be information that's relevant to a larger percentage of the female population and would eliminate one unique environmental factor (being raised with a male twin you are competing with for attention, etc) that could singlehandedly cause the problem.
6
Something not taken into account is that most likely the male twin got more attention, more accolades, more reinforcement while growing up. The girl was likely more often overlooked and pushed into the background.
42
Here we go with the pseudo science of most epidemiology. Sounds like half baked associations at best, or just looking for headlines for the next grant. So did they compare this so-called twin phenomenon against girls with non-twin brothers vs. girls with sisters? To assert that certain specific social behavior is derived from in utero hormone exposure is dubious to absurd. Homo Sapiens Sapiens is unique. We are not governed primarily by biological instinct but by social relations. Obviously girls with brothers are going play differently than girls with sisters. That has more to do with patriarchal social expectations and license than hormones. Then this, 'gee wiz' why don't they perform better later in life? Perhaps the social license they had as girls with brothers doesn't conform to the models of docility for women on the job and in marriage? Perhaps this has nothing to do with hormones but with the nature of social oppression of women? Statistics are not science.
26
Way to take a very simple result and tell a very complicated and speculative story about it.
16
Great now we get to blame ‘baby men’ as yet another reason for why women are not successful. And no surprise that girl babies are selfless saints who completely allow the male twin to evolve as destined. I’m starting to believe that these scientists are seeking to prove we are but a rib off Adam. So what exactly is the aim of their study? Abort the unsuccessful female fetus instead of allowing it to live an ‘unproductive’ life? Reduce testosterone so both the boy and girl can be equally unproductive?
Perhaps before funding such studies, one needs to ask whether there is clarity in the question being researched. And I thought Norway had a good school system. Suddenly STEM in the good old USA seems wonderful.
2
Men do not have all these advantages in society overall; it's just that men have been in the workforce longer, so they're better at it.
Outside of work, men are, by a large miargin in every one of these categories: more likely to be killed (either murdered or in war), or by suicide, imprisoned, depressed, homeless, etc. And at work, men are, by a large margin also willing to work outside and in difficult and dangerous circumstances. How is all of this male privilege?
And far more men then women also strive for the power and money that CEO's have but come up short; they can blame men for that -like all feminists do- or realize that it's their lack of IQ or family-status or other things outside their control. Men don't have it so easy.
7
Just how does a female fetus in utero get exposed to a higher level of testosterone due to the presence of her twin brothers? Does their testosterone actually affect the physiology of the mother who is carrying their future sister? Without this relationship being established in the story, we can't very well draw a line to the supposed effects.
1
@Brian So, upon second reading, it appears the study is about fraternal twins with a girl and a boy together in utero- not identical twins who must be same-sex. My bad. I just wish the article had spelled this out early on. The kids in the photo look like identicals- two girls, two boys.
2
Hormone scientist: Be careful not to draw simplistic conclusions about the effect of hormones on behavior
Article: *draws simplistic conclusions about the effect of hormones on behavior*
32
"The researchers said the effects were because the women were naturally exposed to their brothers’ testosterone in the womb."
And I suppose an ensuing study will claim that men with older twin sisters are more effeminate...
Both male and female fetuses are exposed to high levels of their mother’s’ estrogen. It is the testosterone produced by a male fetus’s testes that causes sexual differentiation.
18
@Nancy
Actually its androgen that produces differentiation.
1
I'm all those things as a twin sister
3
Of course...blame the guy...sexism in the womb
3
@K.Walker Hey neighbor! Nobody is blaming the twin! Intuitively, I would have predicted the sister to do better than average as she would might have an advantage with navigating male networks over her sisters who lack a close male peer.
I get the knee jerk sensitivity...not everything is the fault of white men or baby boys....
4
As the grandpa of two, identical twin three-year-old boys, I think I see a potential solution to the persistent problem of gender discrimination: We need more twin brothers in this world.
To hell with gender stereotypes. Full speed ahead. Sibling coconspirators bringing down the old system; establishing a wiser, better-informed, more equitable system in its place. My grandfatherly heart swells with pride at the very thought.
Bring on the granddaughters. Move over boys, you've got company.
Gramps
6
Attention copy editors:
"Women with twin brothers" is the plural of "a woman with twin brothers." That describes 3 siblings, two male, one female. What you mean is "Women with a twin brother."
68
@Robert, You are addreessing a null set. The NYT no longer has a dedicated copy editing department. Speaking as an ad hoc copy editor for friends I see the lack of precision this causes quite often on the website.
13
@Robert
Yes! I thought the article was about women who grew up with twin brothers, i.e. two siblings. Needs a correction.
14
@Robert I also read it your way at first. I thought, wow that's a really specific study!
11
I am the female half with a twin brother born in the 50's. Some of what the article says fits and for years my husband has opined that testosterone in utero may have had some effect on my personality...driven, and the most successful academically & financially, in my family. I used to be protective of my twin brother who was very quiet & shy. If he was picked on, I defended him and at one point punched & kicked a bully to defend him.
I was always encouraged academically by my parents and teachers. So I suspect cultural differences have something to do with some of the statistics in Norway...in many cultures males get more attention and encouragement than females, even if not overtly and that would have a huge impact on the female's success.
I married in my 30's and never wanted children, instead focusing on my professional career. Testosterone may have something to do with aggression in females but I suspect how the culture directs it, is more important.
9
@JoKor
Ditto JoKor...I too was born in the 50's, in Wisconsin and have a twin brother. Although the oldest, I was always the more dominant and headstrong at home and at school. I've stumbled upon similar research in the past and it's always sparked some glimmer of recognition in my own story. How the exposure to higher levels of testosterone in utero in our case manifests in later life certainly depends on lots of extraneous variables. However, this experience in an of itself can help explain a lot! I look forward to more research outcomes in this area.
6
This is a bizarre conclusion. Twins are at a disadvantage because they are usually born premature. They may tax their parents finances, energy, time and resources and so on because there are two of them. There are many other factors that may explain these outcomes.
The study should have compared these outcomes btn siblings and not btn groups of girls with twin boys and boys with twin boys. It is highly likely when looking at individual sets of twins we would see similar outcomes btn the siblings suggesting that any differences found in among groups would be based on other factors.
The researchers compared women with male twins against women with female twins, so the added burden of having two children was compensated for. They also looked at cases where the twin died in early childhood, to isolate the effect of testosterone away from growing up with a male twin. It was a well designed study on a large population published in a reputable peer-reviewed journal.
22
This may be true, but what about girls with higher levels of testosterone without a twin? Or men with lower testosterone levels? As this is something that varies from person to person, the real issue is not about testosterone levels but about gender roles. If there is a greater tolerance of a variety of behaviors in both genders, we have a more equitable society. This is about the need for cultural change.
28
Anecdotally speaking from personal experience, this is nonsense.
9
@RobReg
It would be a challenge to know this from personal experience. Only by aggregating data, would it be possible to see this. I was surprised by the result but I’d like to know the magnitude of the association and statistical significance.
8
Once, just once I'd like to see an article written that women fail on their own accord and are not subject to some biological or social function of a man. We're not the ones who ate the apple and after all we gave up a rib for them. Jeez.
5
@Kurt Pickard Geez Louise! Nobody is blaming the baby boy. It's hormones.
Don't bring up the apple! We're still sensitive to the 2000 years of temptrous trope we've had to deal with....
We do appreciate all the spider killing you've done for us over the years!
5
Again, biology is your destiny, cisgender women and men.
2
@JY What does that mean? Also, what is "cisgender"? I'm a woman, born female. I am the female gender. It doesn't need any other prefix or label. There are two genders- male and female. You can feel like whatever you want to feel, dress however you like, identify however you like, but that doesn't negate reality.
13
This article is wildly speculative, extrapolating sweeping conclusions from limited findings with some mumbled fine print.
This research paper did NOT look at testosterone. It did NOT look at parenting techniques. It does not give us any idea how testosterone or parenting or socialization affects the outcomes of girls. At best the paper suggests that future studies on those questions could be fruitful.
The New York Times should be held to a higher standard of science journalism than this. This article is essentially clickbait.
114
I am not automatically jumping on the bandwagon. Twins are a greater financial, physical and emotional burden on singletons and until recently any "extra" anything went to the boy. My own aunt is a female twin raised in the 50's and despite being the better student could not go to college since the money obviously went to educate the boy.
The only control is females with a dead twin brother but that would be a small sample introduce a whole host of environmental variables.
18
Agree with you, however the article did mention a study where they looked at girls whose twin brothers had died young and they found the same results. My question is, if the main study cited compares girls with twin brothers to girls with twin sisters, did they omit girls with identical twin sisters from the control group? Seems to me that the experience of growing up with an identical twin must be different from having a fraternal twin, even if both are female.
6
@Allright,
These are people born in Norway "a few decades ago". That is after the oil boom's full effect of economic plentitude for virtually everyone (c.1980). Norway has been a nearly unique society for about 4 decades now, being both wealthy and egalitarian. Had your aunt been born in Norway in 1982 she would have had a free ride to college and a lot of other benefits.
Knowing what I do about Norway I am always a little doubting about applying their admittedly well meant population studies to the wider and meaner world.
3
They were also less likely to graduate from school, marry and have children.
Why are these considered negatives?
17
@Robert Roth. I get what you mean, but education is positively correlated with a lot of things people want - long-term financial stability (despite student loans), more career choices, better health, much lower divorce rate, and a number of positive predictors for your children (their future education level, for one). And marriage is I guess standing in as a marker for having stable, long-term relationships, which while not a goal for everyone, is something that most people seem to want. If you are both educated and married, you are doubling up on your financial advantages and also have a better chance of your marriage working out and being beneficial. For having children, that's obviously a personal choice and I don't know the numbers on the numbers of people who want children vs. who have them. In a way these are just metrics our society uses, but they are also all rewarded by society in sometimes very material ways.
5
We should be looking at why girls do better in school than boys. Is it because schools are designed around the characteristics found more in young girls than in young boys? If that is true shouldn't we be looking at ways to design a school system that encourages learning and growth for both boys and girls?
6
I'm a female with a twin brother. I'm also a social scientist with not only a doctorate, postdoctoral fellowships, and an another advanced degree. I had a successful professional career, as did my twin, and we were the exceptions in the family. This article is speculative; and a short paragraph is given to the power of socialization but, maybe especially for those of us raised in the mid-twentieth century, gender socialization was a powerful norm. Testosterone levels fluctuate across one's life. We have no evidence testosterone during fetal development affects behavior. An absurd article.
23
@Teresa You could not be more wrong. There have been thousands of studies on the effects of prenatal testosterone exposure, and it has been firmly established for decades that testosterone during development is responsible for the growth of male genitalia and the expression of male behavior, both in childhood and adulthood. Expose a fetal female to testosterone (or more accurately its metabolite dihydrotestosterone) and she will not only exhibit male-like behavior as a child and adult, her genitals may also be masculinized. Conversely, a male fetus with the rare condition Androgen Insensitivity Syndrome does not react to his own internally-produced testosterone, and he is born with female genitalia and and displays female-typical behavior in childhood and adulthood.
Perhaps that is the difference between social scientists and real ones - the latter base their claims on careful experimentation rather than the dictates of trendy gender politics.
8
@Teresa — From the article:
”In humans, amniotic testosterone levels are positively related to rates of male-typical play behaviors in both male and female children (4), and chromosomal females with genetic abnormalities that increase prenatal androgen exposure similarly exhibit male-typical behaviors across the lifespan (5).”
Yes, it's complicated, but I wouldn't say there is no evidence of such an effect.
6
@JBR
1) Androgen is what creates the differentiation
2) definitions of "male"/ "female" behavior are notoriously sexist and old-fashioned. Researchers assumed females were into weddings and not into sex, careers or masturbation (the latter even though the Kinsey report told them this wasn't true). When studies revealed one behavior they assumed all even when they study didn't show it, or contradicted it.
4) How we define aggression, ambition , risk-taking is fundamentally sexist. For example, nobody considers wanting a child a risk-taking venture yet it is far more risky than many traditional male hobbies that are seen as signs of male "risk taking". We don't see coaching a kid's sports team as "nurturing" either.
2
Did the writer consider that a woman who is a sister of twin boys could have been born before the twins, thereby not being exposed to the same conditions in the womb as a woman born after? Seems this important distinction wasn’t made.
2
It seems to be an assumption here that the female child is younger than the male twins - how else would she be exposed to testosterone in utero?
I notice this oddity because my daughter has younger male twin brothers, and there's been no effect like those described in this report.
3
The study is looking at fraternal twins where one is a boy and one is a girl.
7
The headline should read "Women with A Twin Brother Are More Likely to Face Penalties at School and Work."
"Women with Twin Brothers" are either older or younger than the twin brothers, or are triplets/quads.
I spent half the article trying to figure out how a girl with older/younger twin brothers could be impacted by uterine testosterone!
54
The article is very poorly edited. NYT, hire better or more (are they overworked?) editors!!
16
Sam I Am—Thank you so much for this comment. I was confused as well, and comments here from other readers suggest they were also bewildered. Your headline is perfect; I hope the NY Times editors will make this correction—in the headline and in the first sentence of the story (i.e., the lead or lede), which now reads, "Women with twin brothers do worse in school and make less money than those with twin sisters, a large new study has found." (The headline writer likely drew on this sentence to write the puzzling headline.) The fact that the study is about "women with a male twin" is not plainly stated until the eight paragraph of the story, by which point I expect a number of readers may have given up in confusion. Thank you again—and here's to clarity in writing and editing!
11
@Sam I Am Yes, the headline is imprecise, and the whole article is riddled with unclear and incorrect language. I can only imagine what it looked like before it was "edited"!
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The article misses a few important things that need explanation. The mother is supposed to have higher levels of testosterone in the womb -- is this something natural to the woman, does it make for a higher likelihood of male foetuses, or does the doubling of males in utero produce more testosterone in the womb? Did it matter whether the female child was born before or after the male twins?
@John Crowley The biological sex of the baby is determined by the sperm, which will provide either an X chromosome (baby will be biologically female) or a Y chromosome (baby will be biologically male).
"the women wound up earning 9 percent less. They were also less likely to graduate from school, marry and have children.
The researchers said the effects were because the women were naturally exposed to their brothers’ testosterone in the womb"
But wait, are we supposed to believe that biology matters?
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This entire article is skewed toward a hormonal theory buried in grand social generalizations. Who says testosterone is the villain in this scenario? The word 'might' is in the text but buried under the article's bias. Fact is, the twin brothers will attract more attention to themselves from parents, grand-parents, neighbors, etc. This alone will account for less props offered to the sister, and might affect her future performances. Dr. Mehta's dismissive caution is key-- but only mentioned in the middle of the article.
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Testosterone and estrogen are not antagonists. It's misleading to to suggest they are. Testosterone may be a counter productive influence in today's more rational society. To view testosterone as a competitive force is anthropomorphic. It's also to view biology as essentially male. School and workplace are not constants nor are they natural environments and therefore, using them as reference points in a study that pits hormones against each other is bad science and male biased.
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The sample size is too small to matter.
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Oh give me a clone!
Of my very own,
With the Y chromosome
changed for X...!
( Isaac Asimov )
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My sister and I were sitting together when I read the headline, and we both said “What???” We are women with twin brothers, but we are not twins. Please clarify your opening. We did not realize you are talking about sets of twins until the second paragraph; therefore, this article does not apply to us.
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I've never felt this compelled to comment on an article that seems so absurd. I am male, whose identitical twin brother died at birth. I also have two younger sisters, both of which are successful in their fields. Are you saying if my twin was alive that my sisters would be negatively impacted emotionally, financially, and behaviorally?! I for one would do anything to ensure that my twin would be standing here today alive. I think the pain of death more than compensates for any negative effect my brother would have had on my sisters, which would be 0 in any case. Absurd.
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@ConcernedVoter You misread the article. The study was of male-female twin pairs compared to female-female twin pairs. It has nothing to do with girls who had older male twin siblings.
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What about the hormonic exposure of the boy to the girl's?
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The article is not clear at first in explaining the situation they investigated. I thought at first it referred to the situation in my family, where my two daughters were followed by brothers who are twins. Thus, my daughters are girls who have twin brothers. But after reading much further, I realized it means girls who are one of a pair of twins where the other is a boy.
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I am a female and have a male twin brother. I have a successful career, am married and have children. I get the concept of sample size but I wonder if this study misses causation for correlation. There are innumerable nurture factors that can negatively impact twins. I see it myself now that I (a girl/boy twin) have girl/boy twins. I wonder if this study gives sufficient weight to those nurture factors which may be prevalent across the board.
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Okay, so let's take the writer's premise that testosterone is a toxic hormone which hurts girls and women throughout life. One "remedy," we are told, is that, "The findings could inform parents, doctors and teachers about ways to support these children, the scientists said."
How about using these finding to support BOYS, who are more affected by testosterone and do more poorly in school?
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@A Doctor
Boys tend to proceed to do fine in the workplace, whereas girls that have twin brothers, as stated in the article, tend to make less money in their jobs etc. They may initially do poorly in school, but school is primarily a simple preparation for work, and boys seem prepared.
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@Sam
"Boys tend to proceed to do fine in the workplace"
You need to check your assumptions here. The number of working age men who are out of work or struggling to hold a job is huge.
2
@Teal. There's not much of an unemployment gap by gender in the US (there is an employment gap that favors men, but that doesn't account for people who selectively choose not to work as could be the case for some mothers). However, there is a gap in how men and women are treated in the workforce, how easily they can move up the ladder, and there's an overall persistent wage gap, although it can vary by sector. I think the point was, though, that women are often viewed negatively when they portray traits that are viewed positively in men, such as risk-taking, assertiveness. These are the very traits that also predict greater success in many work environments, and lead to promotions and the like. Women also often take on extra work that is not rewarded or even recognized but that needs to get done in order for things to function - I see this happen in my field all the time. Of course it's not always the case and individual experiences vary, but it's the situation overall.
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Thanks to all for breaking down the data!! I am always suspicious of studies that find a biological basis for gender behavioral differences. Generally you can find a flaw in the study design or interpretation that we will look back on in 10 years with embarrassment. For now, I remain curious but am not convinced of the testosterone theory.
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This study does not lead to meaningful conclusions. Take:
"In the Norway study, the effects on girls’ educational achievement — perhaps because of more disruptive behavior and less focus in the classroom — probably drove the long-term economic effects, the researchers said."
Does that sound like good science?
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@Teal — The research found that about half of the differences in long-term economic effects (employment, earnings) were linked to the differences in education level. That is a meaningful conclusion and part of a scientific argument.
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I found this summary quite frustrating because it took so long to explain the evidence why this is not an effect of socialization, and the strength of the result is unclear. We finally learn females with male twins were compared to females whose male twins were lost quite early in life. However, with p-value-driven statistics it’s trivial to fail to reject the null model (here, adverse effects of male twin) if your sample (females with male twins who died early) is small. So I went to the paper (because insomnia/procrastination) and saw very wide confidence intervals for the latter group, frequently overlapping zero. What was impressive, however, was that they all trended in the same direction as the original sample. (I didn’t bother to check if the surviving v non-surviving groups were separated completely, or if one contained the former; I hope the latter.) But it seems another proper control in this case would be females who lost a non-twin brother or a female twin sibling in the same period—perhaps there’s something deleterious about early deaths that also changes the survivor’s prospects. I couldn’t see such a comparison anywhere in the paper, although I didn’t scour it.
Tl, dr: I hope journalists can help readers think through scientific results more clearly and carefully. My non-scientist relatives often get the impression there’s not much scientific progress when seemingly conflicting papers are given comparable, uncritical attention in the news.
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@Scientist
Thanks for the helpful comments. As a twin brother to a twin sister this discussion did not ring true to me at all. The statistical comparisons mentioned in the article seemed weak at best and contrived at worst.
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@Scientist — In the figures, every "opposite sex effect" is a comparison of female–male pairs to female–female pairs. The "co-twin death" effect is comparing females who lost a male twin to females who lost a female twin.
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@Scientist
I concur. By the middle of the article, my head began to hurt from shear frustration. Actually, it started after reading the second paragraph "The researchers said the effects were because the women were naturally exposed to their brothers’ testosterone in the womb." I thought the entire article was all over the place with the smattering of disjointed details not flowing very smoothly and with little continuity.
10
I am the female half of twins, born in 1949, and have always wondered if in utero exposure to testosterone might be an explanation for aggression that I have always had. I used to actually fight kids that picked on my brother when we were kids, but the opposite was never true. Unfortunately, I also grew up knowing that I was equal if not superior to any man, which did not jive with the times, and that is another lifelong fight I have struggled with. There have been many fights and examples.
I did very well in school, much better than my twin brother, but was not encouraged to reach higher, and went to a Catholic High School, where there was little encouragement for anything for girls. I did have some college, but have always been and worked as an artist since I was 18. I married, and have two wonderful sons, have been divorced for a long time. I was to make a living, not well off by any standards, but content now.
I think this research is very true and have always believed that this could absolutely be the reason for much of my behavior, beliefs and struggles, as I have always been aware of the differences between myself and other women.
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It feels nice not to fall into a category or study. I'm male, with a twin sister, she is married, and has a son. She has always had a successful career as a scientist. She makes more than her husband, although salary shouldn't be used to determine success. Me: I have had huge fluctuations in my career as a designer, and I'm not married.
18
I agree with Nick. There seems to be an assumption in this article that the childhood behavior of girls with twin brothers has something to do with exposure to testosterone in utero, but there is no discussion of the obvious: some parents may treat their young daughters differently than they treat their young sons, and the difference in how babies are treated has a dramatic effect on a their emotional and psychological development. As a girl gets older and realizes that her twin brother is treated differently by her parents and society, and has advantages she doesn't have, it has to have a huge effect on her development and self esteem.
Besides all this, do fetal boys really have significantly more testosterone than fetal girls? It's an honest question. The author admits that the level of testosterone in utero hasn't been measured. I'm not a doctor, but infants don't have high sex hormone levels, period, so I find this hypothesis a little suspect.
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The mother produces testosterone in utero when there is a male fetus.
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@A
A little testosterone has a profound effect. There are different testosterone levels in utero of the male embryo. This is what causes induction of male genitalia, in part.
This study makes perfect sense to me. And it demonstrates the valuable inferences scientists can make using statistical methods.
9
@A Parents treat their boys much better than their girls. A very sad and unjust practice where both models are pathetic. I had to choose my own judgement over their's. I was never able to bond with either one.
This article misses an important detail of the paper. My first thought when I read about this study was that the authors were ignoring the alternative hypothesis that female twins fare poorly because of socialization that favors their twin brothers (e.g. parents devote more attention/resources to the male twin, teachers grade the female twin more harshly in comparison to the male if they take classes together).
However, the authors attempted to control for socialization by analyzing a subset of their data in which the male twins died early in life (shockingly, around 10% of twin pairs). Some results were similar, others weren't statistically significant. The authors claim that the effect sizes are similar even in the set of subjects with a dead twin, but looking at the data it is clear that there is also greater variance.
Nonetheless, it is premature to claim that testosterone is the explanation for these data. Testosterone is not the only maternal compound that influences development in utero. For example, zinc and cortisol exert many effects on prenatal development (some of which may be sex-specific). These and other molecules are influenced by diet, so an alternative hypothesis would be that mothers who know they are pregnant with opposite-sex twins alter their diets somehow (perhaps they consume more protein because they want their baby boys to be strong). A future study should measure prenatal and adolescent hormone levels in male-female vs female-female twin pairs.
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@Nick This study looked at twin pairs in a time period when most parents did not elect to know the sex of their children.
9
@Nick — That's good thinking, but the alternative hypothesis is still pretty weak.
This methods for study are not described well enough to tell for sure, but it seems exploratory. That is, you start off with the idea that greater testosterone exposure in utero will matter, and then you look for differences between women with female and male twins. Even with a big sample size, with multiple comparisons you may well find differences just by chance. This work should be replicated by another study looking at the same differences before the findings are given much weight.
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@John Williams
That's the point of the large sample size -- to make it much less likely that the result is from chance. Generally as sample size increases, effects from randomness decrease.
4
@John Williams
John Williams provides a very good explanation of why exploratory studies may provide findings that later fail under replication attempts. The large sample size is not enough protection when the number of possible comparisons which can be made is also very large. Studies such as this one are for useful for generating hypotheses for further study; not for providing definitive conclusions.
7
@AN — You should be able to quantify that assertion.
Aren't there also studies that show that women who are female-female twins have a higher rate of developing eating disorders than women who are part of a female-male twin pair? In that case, the higher estrogen exposure seems to trigger something biological.
It does seems to be the case that you can't win, as a woman, if your society is already sexist. If you act more like a man, you are punished for not being warm and likable enough at school and at work. If you double-up on your female gender hormones before birth by having a female twin, you are more likely to develop an eating disorder and body dysphoria.
Can we please stop telling women to just "lean in" -- and work instead on fixing systematic sexism in society as a whole?
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