[Paleopsych] Edge:The Assortive Mating Theory: A Talk with Simon Baron-Cohen

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The Assortive Mating Theory: A Talk with Simon Baron-Cohen

[The sidelining of 20th century egalitarian dinosaurs continues.]

                           Edge 158-- April 6, 2005
                                (6,900 words)

    My thesis with regard to sex differences is quite moderate, in that I
     do not discount environmental factors; I'm just saying, don't forget
    about biology. To me that sounds very moderate. But for some people in
    the field of gender studies, even that is too extreme. They want it to
    be all environment and no biology. You can understand that politically
     that was an important position in the 1960s, in an effort to try to
    change society. But is it a true description, scientifically, of what
    goes on? It's time to distinguish politics and science, and just look
                               at the evidence.


    THE REALITY CLUB: Marc D. Hauser, Steven Pinker, Armand Leroi,
    Carole Hooven, Elizabeth Spelke respond to Simon Baron-Cohen [below}


    Simon Baron-Cohen is Professor of Developmental Psychopathology and
    Director of the Autism Research Centre at Cambridge University. In
    this Edge feature, he presents his new Assortative Mating Theory which
    connects his two fields of research: the characteristics of autism in
    terms of understanding what's going on in the brain and the causes of
    the condition; and understanding the differences between males and

    "My new theory is that it's not just a genetic condition," he says,
    "but it might be the result of two particular types of parents, who
    are both contributing genes. This might be controversially received.
    This is because there are a number of different theories out there --
    one of which is an environmental theory, such as autism being caused
    by vaccine damage -- the MMR vaccine (the measles, mumps, and rubella
    combination vaccine). Another environmental theory is that autism is
    due to toxic levels of mercury building up in the child's brain. But
    the genetic theory has a lot of evidence, and what we are now testing
    is that if two "systemizers" have a child, this will increase the risk
    of the child having autism. That's it in a nutshell.

    Baron-Cohen realizes that his theory might raise anxieties. "Just
    because it's potentially controversial," he says, "doesn't mean that
    we shouldn't investigate it. And there are ways that you can
    investigate it empirically."
    He also expects controversy. Given the continuing public discussing in
    the US about innate sex differences, he will, no doubt, be challenged
    when he says "It was interesting for me to discover that there's been
    a sleight of hand, mostly in the States, such that the word 'sex' has
    been replaced by the word 'gender'. Baron-Cohen believes that it's
    time "to distinguish politics and science, and just look at the
    evidence". Others will feel differently.


    SIMON BARON-COHEN is Professor of Developmental Psychopathology and
    Director of the Autism Research Centre at Cambridge University. He is
    also a Fellow of Trinity College, Cambridge. His books include
    Mindblindness; and The Essential Difference: The Truth about the Male
    and Female Brain.

    [14]SIMON BARON-COHEN's Edge Bio Page

    (SIMON BARON-COHEN:) I've been working on the question of autism,
    trying to understand what characterizes autism from a psychological
    perspective and ultimately aiming to understand what's going on in the
    brain and the causes of the condition. My new theory is that it's not
    just a genetic condition, but it might be the result of two particular
    types of parents, who are both contributing genes. This might be
    controversially received. This is because there are a number of
    different theories out there -- one of which is an environmental
    theory, such as autism being caused by vaccine damage -- the MMR
    vaccine (the measles, mumps, and rubella combination vaccine). Another
    environmental theory is that autism is due to toxic levels of mercury
    building up in the child's brain. But the genetic theory has a lot of
    evidence, and what we are now testing is that if two "systemizers"
    have a child, this will increase the risk of the child having autism.
    That's it in a nutshell.
    A systemizer is somebody whose style of thinking is predominantly in
    terms of understanding things according to rules or laws. You can
    think of lots of different kinds of systems: mathematical systems
    (algebra, computer programs), or mechanical systems (computers or
    cars); natural systems (weather, or rocks, geology); and social
    systems (businesses, or the military).
    In each case, when you systemize what you do, you try to understand
    the system in terms of the laws that govern the system. Economics
    would be an example of a system, where people are trying to predict a
    crash, or predict what's going to happen in terms of stock markets.
    They are trying to understand things according to laws or rules. The
    theory we are testing is that if you have a mother and a father who
    are both systemizers, the risk of the child having autism increases.
    Systemizing is expressed in behavior, so, for example, if your hobby
    is playing with computers, that's the behavior that you see. But
    obviously such activity reflects your interests, which is what's going
    on in your mind, not just in your behavior. The mind of a systemizer
    is drawn to understand systems. Steven Pinker has a nice phrase about
    spiders, that spiders are just programmed to spin webs. He uses that
    as an analogy for the way in which a typically developing child is
    programmed to learn language. These programs are not a hundred percent
    deterministic; you can intervene, you can change. There's obviously
    plasticity in the system. In the same way, systemizing isn't going to
    turn out to be a hundred percent genetic. There are few if any
    behavioral characteristics in humans that are one hundred percent
    genetic .
    There are five steps for testing this theory. First, we need to
    establish whether or not systemizing runs in families. Secondly, we
    need to find out if there are there any genes associated with
    systemizing. Thirdly, are the parents of children with autism
    systemizers, defined according to their cognition? Fourthly, do they
    both carry the genes for systemizing? Finally, when these gene
    combine, does this raise the risk of their child having autism?
    This theory will be controversial, and it might raise anxieties. But
    just because it's potentially controversial doesn't mean that we
    shouldn't investigate it. And there are ways that you can investigate
    it empirically.
    How would you investigate it? Well first thing is to look at families
    where there's already an autistic child, and look at the parent
    directly. We've already conducted some of those studies, and found
    that whereas in the general population systemizing is more common
    among males, in the case of parents of a child with autism, the mother
    of such a child is also very likely to be a systemizer, with
    male-typical interests.
    One example of how we test this is to give them a task where you have
    to analyze a visual pattern as quickly as you can to find a component
    part. In the general population males are quicker at this kind of
    analytic task, but in the case of parents of children with autism, the
    mothers are just as fast as typical males. The mothers are showing a
    typical male profile, and that's counter-intuitive since you would
    expect them to be showing a more typical female profile. That's just
    one clue that this theory is worth exploring.
    A second clue is that we've looked at the rates of engineering in both
    fathers and the grandfathers of children with autism. Engineering is
    an occupation where you have to be a good systemizer, for example,
    understanding mechanical systems. We found that fathers of children
    with autism are over-represented in the field of engineering. And what
    was interesting was that we found exactly that same pattern in the
    grandparents too.
    You start with the child with autism; he or she is the end result of
    this experiment of nature. And you work backwards to see if there were
    there clues in the previous generation -- or previous two generations.
    This new theory is called "the assortative mating theory", The clue
    that both sides of the family are contributing similar genes is that
    in our study of occupations, grandfathers on the maternal and the
    paternal sides were both more likely to be working in the field of
    engineering. So the strong systemizing wasn't coming down just one
    side of the family. It's called assortative mating because it
    describes the idea that two individuals might end up in a union
    because of having similar characteristics. They're selecting each
    other on the basis of having similar characteristics.
    The assortative mating theory connects with the field of sex
    differences -- my other big area of interest . I've been trying to
    understand the differences between males and females. It was
    interesting for me to discover that there's been a sleight of hand,
    mostly in the States, such that the word 'sex' has been replaced by
    the word 'gender'.
    This has happened in a very subtle way over the last century, so that
    in the States, nobody talks about sex differences; they talk about
    gender differences. Whenever you want to refer to somebody's sex you
    refer to their gender. I call it a sleight of hand, because actually
    'sex' is the older word. Your sex is either male or female, and in
    biology your sex is defined by whether you have 2 X chromosomes or an
    X and Y chromosome. There's been a subtle shift into talking about
    gender, to whitewash the word sex.
    Why has this happened? Presumably, because your sex is determined by
    your chromosomes. And in the States the ideology is that we shouldn't
    be determined by anything; we should be able to be anything we choose.
    The blank slate. Gender refers to how you think of yourself: as
    masculine, or feminine, It's much more subjective, and is commonly
    believed to be culturally constructed. Italian male gender behavior is
    expressed differently from English male gender behavior. This gives
    the impression that people's gender behaviour can change as they
    change culture, even if their biological sex is fixed.
    Talking about gender is therefore much more optimistic than talking
    about sex. It's the rags to riches idea -- you can become anything.
    But I've been very interested to go back to the original notion of
    sex, as a biological characteristic, and to ask if there are there any
    essential differences between males and females in the mind. And to
    understand that if there are psychological differences, what are the
    biological mechanisms that give rise to these? Are they genes, are
    they hormones?
    In our own work, we have been focused very much on fetal testosterone
    -- the hormone that the fetus is producing in the womb, to see whether
    that has any effect on later behavior.We had a perfectly good word,
    which was sex. But it's become almost a profane word in the U.S. I
    recently wrote a journal article on sex differences in the mind.
    Everywhere I'd written the word sex, the copy editor changed it to the
    word gender. A systematic change had been introduced, and I asked that
    the original word be used. The editors asked me to give them a good
    reason, because they explained in the States the preferred word is
    gender. I had to explain, a person's gender is different to their sex.
    It's a distinction that seems to have got lost. It's hard to know
    whether it was deliberate, or whether it just happened without anybody
    Back to hormones. We've been conducting laboratory studies on the
    amniotic fluid in the womb -- the fetus is effectively swimming in
    this amniotic fluid. We analyze how much testosterone, the so-called
    male hormone, is in the amniotic fluid. It's not actually a male
    hormone, because both sexes produce it, it's just that males produce a
    lot more than females. That's because it comes from the testes.
    Females also produce it in the adrenal glands. And even within the
    boys, or within the girls, you see individual differences in how much
    is produced.
    The question is, does this translate into anything psychological if
    you follow up those children? We measured the amniotic fluid
    testosterone, then waited until the baby was born, and then looked at
    the baby's at 12 months old, 18 months old, two years old. It's a
    longitudinal prospective study.
    What we found is that the higher the baby's level of fetal
    testosterone, the less eye contact the child makes at 12 months old.
    And also the slower they are to develop language at 18 months old. To
    me these are really fascinating results, because we're looking at
    something biological, in this case a hormone which presumably is
    influencing brain development to produce these quite marked
    differences in behavior. We always knew that girls talked earlier than
    boys -- that there is sex difference in language development -- and we
    also knew that there's huge variability at 18 months: some kids have
    no words at all, and other kids have huge vocabularies, about 600
    words. No one's really been able to explain this variability. Why
    should one kid be almost mute and another kid be very verbal?
    People have identified some factors, such as that first-born children
    talk earlier than later-born children. Obviously there are
    environmental factors that are relevant. Presumably that's because
    first-born children get much more attention from their parents. But
    over and above your birth order, it looks like hormones also explain
    some of the variability. We've now followed up these kids into school,
    they're four years old, and we're still finding that the prenatal
    hormone production levels are influencing behavior in middle
    childhood. This is just one example of why we shouldn't ignore biology
    in explaining differences in how the mind works.
    I don't argue it's all biology. But for a long time social behavior
    and language development were seen as purely environmental or learned
    experience. These hormone studies suggest hormones are also part of
    the explanation. We also know from medical conditions that if, for
    example, for genetic reasons you have an overproduction of
    testosterone, this condition can change your behavior. So if you look
    at girls with a condition called Congenital Adrenal Hyperplasia (CAH),
    where they are producing too much testosterone for genetic reasons,
    they look like tomboys. Their interests are very male-typical
    interests; they like playing with little toy cars, they like building
    tree houses, and they perform very quickly on spatial tests, unlike
    typical girls.
    The evidence for my assertions comes from experiments. And in all of
    these areas I'm not interested in beliefs without evidence.
    One experiment we conducted here in Cambridge was at the local
    maternity hospital. Essentially we wanted to find out whether sex
    differences that you observe later in life could be traced back to
    birth, to see if such differences are present at birth. In this
    experiment we looked at just over one hundred newborn babies, 24 hours
    old, which was the youngest we could see them, and we presented each
    baby with a human face to look at, and then a mechanical mobile
    suspended above the crib. Each baby got to see both objects.
    Obviously these objects are different in interesting ways, because the
    human face is alive, and it can express emotion, it's a natural
    object. The mechanical mobile is man-made, it's not alive, and
    obviously it doesn't have emotions. We tried to make the two objects
    equivalent in some important ways. One is that they were both the same
    size; another was that they were a similar colour, in order to try and
    control features that might be grabbing the child's attention. But
    effectively what we did was film how long each baby looked at each of
    these two objects.
    We asked the mothers not to tell us the sex of their babies, so that
    we could remain blind to whether this was a boy or a girl. And for the
    most part that was possible. Sometimes it was possible to guess that
    this was a boy or a girl, because there would be cards around the bed
    saying, "Congratulations, it's a boy." That potentially could have
    undermined the experiment, although we then gave the videotapes to a
    panel of judges to simply measure how long the baby looked at the face
    or the mobile. By the time the judges were looking at these videotapes
    they didn't have any of these potential clues to the sex of the baby,
    because all you could see was the eyes of the baby.
    The results of the experiment were that we found more boys than girls
    looked longer at the mechanical mobile. And more girls than boys
    looked longer at the human face. Given that it was a sex difference
    that emerged at birth, it means that you can't attribute the
    difference to experience or culture. Twenty-four hours old. Now you
    might say, well, they're not exactly new-born, it would have been
    better to get them at 24 minutes old -- or even younger. But obviously
    we had to respect the wishes of the parents and the doctors to let the
    baby relax after the trauma of being born. And let the parents get to
    know their baby. So strictly speaking, it might have been one day of
    social experience. But nonetheless, this difference is emerging so
    early that suggests it's at least partly biological.
    The results were published in 2001 in a scientific journal and the
    experiment hasn't yet been replicated, and obviously in science what
    is needed is independent replication. I'll be interested in other labs
    to attempt to do this. As far as I know there hasn't been any attempt.
    This may be because it's quite hard work.
    To test a hundred babies, you have to hang around hospitals waiting
    for babies to be born. That sounds pretty straight-forward, because
    babies are being born every day. In a city like Cambridge there are
    about five new babies born a day. For some reason babies tend to be
    born in the middle of the night, about two or three o'clock in the
    morning. You have to have a very dedicated research team who are
    willing to wait. In Cambridge, mothers only stay in hospital for one
    day. Maybe one night. Then they are sent home, in order to vacate the
    bed for another expectant mother. In terms of your window of
    opportunity for testing babies, you therefore have to be there at the
    right time. We had two very hard-working master's students who
    approached mothers to ask for parental consent -- maybe that was
    easier in a city like Cambridge, because parents know that in a
    university town, research is going on.
    The test is not invasive -- the baby just has to lie on their back and
    look up. They were presented with each object for only one minute,
    because babies tend to get very restless very quickly. It's a
    difficult experiment to conduct, because babies spend most of their
    time sleeping, or feeding, or crying. You have to wait until they're
    not doing any of those three things. When they're awake and calm, you
    have a couple of minutes to present the stimuli.
    The camera is well-hidden off to one side. Babies can't see very far
    -- the depth of vision of a newborn baby is only between 15 and 20
    centimeters. So it is unlikely that the presence of the camera itself
    affected how the baby responded.
    I was expecting the experiment to be received more controversially,
    because as far as I know it is one of the first demonstrations of a
    sex difference in the mind at birth. In fact it was published without
    any fuss. It may be simply that the climate has now changed, and that
    people are much willing to accept that there are sex differences in
    the mind, and that these might even be partly biological. If that's
    true, then this is good news for scientists who are interested in how
    the mind works.
    My thesis with regard to sex differences is quite moderate, in that I
    do not discount environmental factors; I'm just saying, don't forget
    about biology. To me that sounds very moderate. But for some people in
    the field of gender studies, even that is too extreme. They want it to
    be all environment and no biology. You can understand that politically
    that was an important position in the 1960s, in an effort to try to
    change society. But is it a true description, scientifically, of what
    goes on? It's time to distinguish politics and science, and just look
    at the evidence.

The responses:

    [20]MARC D. HAUSER
    Psychologist, Harvard University; Author, Wild Minds.

    It is hard to imagine anyone living today disagreeing with
    Baron-Cohen's starting premise that there are biological differences
    between the sexes. Even the staunchest cultural relativists have to
    acknowledge that there are differences in the sex chromosomes and
    hormonal titers that lead directly to differences in our anatomy.

    Recent work on imprinted genes a class that fails to follow the
    classic Mendelian patterns of inheritance shows that maternal
    contributions are often in complete conflict with paternal
    contributions. For example, with some imprinted genes, the maternal
    copy is quiet and the paternal copy is expressed, causing the fetus to
    extract more from its mother than she would like; these genes often
    cause pregnancy complications such as gestational diabetes. Studies of
    the brain using neuroimaging reveal sex differences in structure and
    function, and work with patient populations reveal differences in
    vulnerability to mental disorder. And closer to home, there are
    massive sex differences in the incidence of autism, with studies
    reporting an 8:1 bias in favor of males.

    Where the debate gets interesting is when one attempts to explain how
    tightly the biology constrains our thoughts, preferences and actions.
    Baron-Cohen's assortative mating hypothesis is an attempt to grapple
    with this issue. Much of the evidence hinges on the early appearance
    of sex-specific signatures of mental function. Early signatures are a
    tell-tale sign of an innate capacity peaking through, but they are not
    definitive. One needs to rule out that the experience obtained is
    insufficient for a learning mechanism to create the capacity.

    And here is where Baron-Cohen's observation that newborn boys like to
    look at mobiles and little girls at faces is fantastic, and just the
    right kind of start into a serious research program on the biology of
    sex differences; these results fit nicely with other data showing that
    for spontaneously generated paintings by young children, little girls
    almost always draw one or more people into the scene, whereas little
    boys rarely do, using their canvas as a vehicle for vehicles, from
    rocket ships to more mundane cars and bicycles.

    But now comes the hard work.

    What is it about the male genome that sets up a preference for the
    mechanical or physical whereas the girl genome leans toward faces and
    the social? How quickly, and with what kind of experience, can these
    initial biases be exaggerated? Why did these differences evolve? In
    the language of Darwin, what selected for this kind of preference? Was
    it our division of labor, with males focused on hunting and therefore
    technology, while females focused on gathering and the schmoozing that
    goes on during this kind of activity?

    One clue that these are evolved sex differences comes from recent work
    looking at the incidence of innovation among primates. Across all the
    primates, including our closest relatives the chimpanzees, males are
    far more likely than females to take the lead in innovation, and much
    of the creativity lands in the domain of tool technology. In contrast,
    for most primate societies, females are for more engaged in the
    intricacies of social life than are males, largely because females
    tend to stay in their natal groups for life whereas males emigrate
    out. If there is a bias toward male folk physics and female folk
    psychology, there may be traces way back to our primate ancestors.

    How are data like Baron-Cohen's reconciled with the fact that for
    imprinted genes, maternally active copies appear to be largely
    expressed in the rational frontal lobes whereas the paternally active
    copies appear to be largely expressed in the emotional limbic lobes?
    Are there in utero battles that arise over the concentration of
    testosterone circulating during development, with paternally active
    genes pushing hard for increased testosterone to push growth and
    toughness? Are maternal copies pushing in a different direction,
    attempting to regulate the physiology in such a way that their
    offspring are social specialists?

    What makes work like this so very difficult, especially in terms of
    selling it to the public, is that more often than we would like to
    admit, reported sex differences either crumble in the face of follow
    up work, or for those differences that have been reported and
    replicated, claims regarding biological underpinnings have fallen prey
    to more experientially-based accounts. One only need think back to gay
    genes and gay brains, and the sad fate of those results. Thus,
    although I am sympathetic to Baron-Cohen's research project and find
    it odd that anyone would consider this work controversial, there is an
    obligation to get the story right here that far exceeds the demands in
    other areas.

    Psychologist, Harvard University; Author, The Blank Slate.

    I find Simon Baron-Cohen's work admirable in several ways. The
    systematizer-empathizer dimension is an interesting new way to capture
    some of the variation between male-typical and female-typical
    cognitive styles. It cuts across motivation and aptitude (which are
    often difficult to distinguish) and might subsume some of the
    long-noted sex differences that have been stated in cruder form, such
    as orientation to objects versus people. I also am intrigued by the
    studies of the effects of fetal testosterone, a valuable new way to
    learn about which psychological sex differences might be consequences
    of the biological programs that build our brains.

    Baron-Cohen wonders why sex is so often referred to these days as
    "gender." Part of it is a new prissiness -- many people today are as
    squeamish about sexual dimorphism as the Victorians were about sex.
    But part of it is a limitation of the English language. The word "sex"
    refers ambiguously to copulation and to sexual dimorphism, and it's
    often important not to confuse them! The linguistic term "gender"
    literally means "kind," as in the cognates "genus," "generic," and
    "genre." Languages often subdivide their nouns into kinds for purposes
    of inflection, such as human/nonhuman, animate/inanimate,
    long/flat/round, vowel-final/consonant-final, and male/female. Many
    Indo-European languages have a gender distinction in their nouns that
    aligns with a masculine/feminine distinction in their pronouns, and so
    "gender" was pressed into service as a way to refer to the difference
    between men and women. Some academics want "gender" to refer
    specifically to socially defined rather than biologically determined
    patterns of sex-typical behavior, but this guideline, like most
    top-down prescriptions about lexical semantics, is rarely obeyed. The
    basic problem is that we have three concepts to convey -- intercourse,
    dimorphism, and social roles -- and at best two words with which to
    convey them.

    I was amused to read that "It may be simply that the climate has now
    changed, and that people are much willing to accept that there are sex
    differences in the mind, and that these might even be partly
    biological." Was this interview conducted before the event that is
    coming to be known as "1/14"?

    [ED. NOTE: The interview took place at Trinity College on 3/12.]

    Biologist, Imperial College; Author, Mutants.

    I take the premise of Simon Baron-Cohen's project -- that there are
    innate sexual differences in behaviour and aptitudes -- for granted.
    As Olivia Judson recently pointed out in a New York Times piece about
    "1/14", it "s hard for a zoologist to suppose otherwise.

    I am not, however, wholly convinced by his argument that autistic
    children -- nearly always boys -- are, in effect, hypermales.
    Baron-Cohen has shown that, relative to girls, boys are good at
    systematising and poor at empathising, and that autistic boys are
    exceptionally so. This fascinating result then raises a question,
    namely, why should these two, seemingly unrelated, attributes should
    trade-off with each other?

    Baron-Cohen's answer seems to be: foetal testosterone. Perhaps
    autistic boys were exposed to unusually high levels of testosterone in
    the womb, so developing the systematising part of their brains, and
    repressing the empathising part. It's an exaggeration of a normal
    process. This strikes me as perfectly plausible, but it also entails a
    number of peculiar, if testable, consequences.
    Testosterone is a hormone and, as such, affects the entire brain and
    body of the foetus. This means that one should expect autistic boys to
    be hypermales not just with respect to systematising and empathising
    -- but in all possible ways.
    Are autistic boys, then, exceptionally aggressive at play? When they
    grow up, are they invariably heterosexual? Do they look exceptionally
    masculine -- that is, are they morphometrically hypermale? And what of
    those rare autistic girls? If they, too, are hypermale due to heavy
    doses of foetal testosterone, should this not be reflected in their
    behaviours, their sexual orientations, their bodies?
    The motivation for these questions is that we do know something about
    the consequences of high foetal testosterone -- witness the Spotted
    hyena. In all mammals, the placenta produces a lot of testosterone.
    This testosterone is, however, broken down into oestrogen by an enzyme
    called Aromatase. Spotted hyenas foetuses have naturally low levels of
    Aromatase, and so are exposed to extraordinarily high levels of
    placental testosterone. The result of this is that females are born
    with large penis-like clitorises that they can jaunt erect in
    dominance displays, fused vaginas and very nasty tempers.
    Now, clearly we can't ask Spotted hyenas to systematise and empathise.
    But we can ask their human equivalents. Loss-of-function Aromatase
    mutations are occasionally found in humans. Like the hyenas, girls
    homozygous for such mutations are born with masculinised genitalia.
    Nothing, I think, is known about their temperaments or talents. Are
    they autistic? Better yet, are their brothers homozygous for the same
    mutations, autistic as well? If Baron-Cohen is right, they should be.
    Of course, even if the hypermale theory of autism is wrong,
    Baron-Cohen's proposed mechanism of assortative mating among
    systematisers could still be right. But let us hope not. Surveying my
    colleagues it seems to me that the reproductive success of gifted
    female scientists is poor enough as it is.

    Lecturer in Anthropology, Harvard University.

    Simon Baron-Cohen's Assortative Mating Theory of Autism is ambitious,
    and demonstrates the usefulness of innovative, "big picture" thinking
    in getting a handle on seemingly intractable problems. The ideas seem
    to fit together nicely to present a clear picture of the etiology of
    autism. The flip-side of big-picture thinking, however, is that the
    authenticity of the full picture relies on the validity of each
    sub-theory; and in this case, the big-picture is painted with a series
    of appealing, yet tentative strokes. Baron-Cohen acknowledges that the
    underlying theories need to be tested, and he presents five
    sub-theories, in the form of testable hypotheses, which focus
    primarily on the relationship between genetics and systemizing.
    His main idea is as follows: people process the world using a
    cognitive style that falls somewhere along the spectrum of systemizing
    (more masculine) to empathizing (more feminine). In systemizing,
    information is processed with attention to rules and laws, and in
    empathizing, processing is biased toward social cues. As autism can be
    characterized by the combination of two extremes -- a lack of
    attention to social cues and a focus on laws and rules -- then it
    follows that, should there be genes for systematizing, two systemizers
    have a higher chance of producing an autistic child. It further
    follows that, should systemizing be a predominantly masculine trait,
    the agent that masculinizes the brain, prenatal testosterone, may be
    also play a central role in both systemizing and autism.
    A wealth of evidence, including Baron-Cohen's own research, links the
    effects of early testosterone to later masculine behavior in humans
    and non-human animals. Some of the most robust research has examined
    the effects of Congenital Adrenal Hyperplasia (CAH), in which too much
    testosterone is produced by the adrenal gland prenatally. Females with
    this condition (whose hormonal levels are normalized at birth) are
    somewhat masculinized--e.g., they engage in relatively high levels of
    rough and tumble play and perform in the male-typical range on spatial
    tests (higher than normal females). If early testosterone increases
    systematic processing and masculine behavior, then it follows that CAH
    boys should also show increased performance on tests of spatial
    ability; but among males, the relationship between perinatal
    testosterone and later spatial performance is equivocal at best.
    Indeed, there is evidence to suggest that excess testosterone in utero
    actually hampers male spatial ability.
    A big-picture, evolutionary analysis of the Assortative Mating theory
    reveals somewhat of a paradox between conventional notions of
    masculinity, and the newer notions of "cognitive masculinity."
    Testosterone can be thought of as promoting behaviors that are
    traditionally masculine, preparing males physically and
    psychologically to bias energetic investment toward mating effort. In
    adult males, high testosterone levels are associated with
    status-seeking behaviors and the pursuit of mating opportunities. In
    men, confidence and social dominance (which would require a relatively
    high social facility) are predicted by high testosterone. The case of
    the classic nerdy scientist conjures up images of the stereotype of
    the low testosterone, but in the current context "cognitively
    masculine," man -- a scrawny male who, although he may be successful
    in the world of technology, is a miserable failure socially and
    The paradox of the two notions of masculinity raises questions about
    the role of testosterone in shaping psychological traits, such as
    status-seeking behavior and spatial ability, in utero and in
    adulthood. With my colleagues Chris Chabris, Peter Ellison and Steve
    Kosslyn, I've investigated the role of testosterone in solving spatial
    problems. We have found that although high testosterone males
    outperformed low-testosterone males on mental rotation tests, the high
    performers gained their advantage not because they were better at
    internally transforming objects, but, as the evidence suggested,
    because they were more confident in their decisions about the
    similarity of objects. Perhaps the paradox can be at least partially
    resolved by furthering our understanding of testosterone's role in
    affecting performance on cognitive tests.
    These findings on individual differences in mental rotation
    performance, along with a relative lack of robust findings on the
    effects of perinatal testosterone, remind us that picture of how
    testosterone affects cognition is still far from complete. While
    evidence strongly suggests that early and late sex differences in
    testosterone levels play a central role in shaping traits that are
    clearly related to mating effort, such as dominance, sexual, and
    competitive behaviors, we should not take for granted that
    testosterone affects cognitive ability directly. More research should
    examine the extent to which the relationship between testosterone and
    cognitive performance is actually modulated by a third variable,
    having to do with dispositional factors such as confidence and
    competitiveness, that are more closely associated with mating effort.

    Psychologist, Harvard University.

    We humans seem to have an abiding need to reduce the richness,
    variety, and complexity of our mental lives to categories. In past
    times, we divided ourselves into the introverts and the extroverts,
    the field-dependent and the field-independent, the visualizers and the
    verbalizers. With the advent of neuroscience came the chance to divide
    our brains into categories as well. That supremely intricate and
    elusive organ became the left brain and the right brain, the grey
    matter and the white matter, the male brain and the female brain.
    Simon Baron-Cohen builds on the last distinction and offers us a new
    pair of categories by which to sort ourselves: we are systematizers or
    The categories of the past have a quaint look about them, because none
    of them has proved very satisfying. Binary categories don't buy us
    much, because humans are both more and less variable than they
    suggest. Two categories are far too few to pigeonhole a species whose
    members can grow from newborn infants to seal-hunters, cathedral
    builders, or capoeira dancers. Yet two categories are also one too
    many. In the right circumstances, all of us become introverted or
    extroverted, swayed by others or steadfast to our principles, visually
    imaginative or verbose. Global categories tend to obscure the
    commonalities in human experience and the common capacities, hopes,
    and failings that define us as a species.
    Is there a male brain, and is systematizing its job description?
    Baron-Cohen asks us to distinguish politics from science and consider
    the evidence. The evidence for an inborn, male predisposition for
    systematizing comes from a single experiment on newborn infants,
    tested with a single person and object. The person was the report's
    first author, who surely knew the experimental hypotheses and who, we
    now learn, may have known the sex of the infants whose attention she
    elicited. The experiment provides no evidence that the basis of
    infants' preference, if real, had anything to do with the categorical
    distinction between the displays. Would infants show the same
    preferences for other face/object pairs? Would they maintain this
    preference if low-level properties of the two displays, such as their
    speed of motion, were equated? One need not object to Baron-Cohen's
    politics to be less than persuaded by his data.
    More important, Baron-Cohen fails to consider the extensive evidence
    that has accumulated, over the last thirty years, on infants'
    developing understanding of object mechanics. Hundreds of
    well-controlled experiments reveal no male advantage for perceiving
    objects or learning about mechanical systems. In most studies, male
    and female infants are found to discover the same things at the same
    times. Both males and females come to see the complete shapes of
    partly hidden objects under the same conditions and at the same ages.
    They figure out how objects support one another, through the same
    series of steps. They reach for objects by extrapolating their
    motions, with equal accuracy. They make the same errors when they
    search for hidden objects, and they get over those errors at the same
    time. Sometimes female infants have an edge: In experiments by Laura
    Kotovsky and Renee Baillargeon, for example, females start to learn
    about the relation between force and acceleration (the harder a
    stationary object is hit, the further it goes) a month earlier than
    males do. Males catch up, however: by 6 1/2 months, you can't tell
    them apart.
    Whatever the newborn infants in Baron-Cohen's experiment were doing,
    the male and female participants in three decades of infant research
    have followed a common path, engaging with objects and people. Infants
    don't choose whether to systematize or empathize; they do both, and so
    do we all. Baron-Cohen's categories may seem as quaint as left and
    right brains by the time his newborn subjects are old enough to read
    about them.


   13. http://www.edge.org/3rd_culture/bios/brockman.html
   14. http://www.edge.org/3rd_culture/bios/baroncohen.html
   20. http://www.edge.org/3rd_culture/bios/hauser.html
   21. http://www.edge.org/3rd_culture/bios/pinker.html
   22. http://www.edge.org/3rd_culture/bios/leroi.html
   23. http://www.edge.org/3rd_culture/bios/hooven.html
   24. http://www.edge.org/3rd_culture/bios/spelke.html

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