The empathizing–systemizing (E–S) theory suggests that people may be classified on the basis of their scores along two dimensions: empathizing (E) and systemizing (S). It measures a person's strength of interest in empathy (the ability to identify and understand the thoughts and feelings of others and to respond to these with appropriate emotions); and a person's strength of interest in systems (in terms of the drive to analyse or construct them).
According to the originator of the hypothesis, Simon Baron-Cohen, the E-S theory has been tested using the Empathy Quotient (EQ) and Systemizing Quotient (SQ), developed by him and colleagues, and generates five different 'brain types' depending on the presence or absence of discrepancies between their scores on E or S. E-S profiles show reliable sex differences in the general population (more females showing the profile E>S and more males showing the profile S>E). Baron-Cohen and associates say the E-S theory is a better predictor of who chooses STEM (Science, Technology, Engineering and Mathematics) subjects than gender is. The E-S theory has been extended into the 'Extreme Male Brain' (EMB) theory of autism and Asperger syndrome, which are associated in the E-S theory with below-average empathy and average or above-average systemizing.
Baron-Cohen's studies and theory have been questioned on multiple grounds. The overrepresentation of engineers could depend on a sampling bias, and analyses of autism have not found that autism clustered preferentially around areas rich in IT industry.
E-S theory was developed by psychologist Simon Baron-Cohen as a major reconceptualization of cognitive sex differences in the general population and in an effort to understand why the cognitive difficulties in autism appeared to lie in domains in which he says on average females outperformed males and why cognitive strengths in autism appeared to lie in domains in which on average males outperformed females.
He had previously proposed the mind-blindness theory in 1985, which argued that children with autism are delayed in their development of a theory of mind, that is, the ability to understand the thoughts and feelings of themselves or others. Baron-Cohen says a strength of this theory lies in its power to explain one of the core features of autism (the social and communication difficulties), but a limitation of the mindblindness theory is that it ignored the other main domain in autism (unusually narrow interests and highly repetitive behaviors, also called 'resistance to change or need for sameness'). To address this, Baron-Cohen put forward the E-S theory.
According to Baron-Cohen, females on average score higher on measures of empathy and males on average score higher on measures of systemizing. This has been found using the child and adolescent versions of the Empathy Quotient (EQ) and the Systemizing Quotient (SQ), which are completed by parents about their child/adolescent, and on the self-report version of the EQ and SQ in adults.
Baron-Cohen and associates say that similar sex differences on average have been found using performance tests of empathy such as facial emotion recognition tasks and on performance tests of systemizing such as measures of mechanical reasoning or 'intuitive physics'.
While experience and socialization contribute to the observed sex differences in empathy and systemizing, Baron-Cohen and colleagues suggest that biology also plays a role. A candidate biological factor influencing E and S is fetal testosterone (FT). FT levels are positively correlated with scores on the Systemizing Quotient and are negatively correlated with scores on the Empathy Quotient A new field of research has emerged to investigate the role of testosterone levels in autism. Correlational research demonstrated that elevated rates of testosterone were associated with higher rates of autistic traits, lower rates of eye contact, and higher rates of other medical conditions. Furthermore, experimental studies showed that altering testosterone levels influences the maze performance in rats, having implications for human studies. The fetal testosterone theories posit that the level of testosterone in the womb influences the development of sexually dimorphic brain structures, resulting in sex differences and autistic traits in individuals.
Evolutionary explanations for sex differences
There are several evolutionary psychology explanations for this gender difference, according to Baron-Cohen. For example, better empathizing may improve care of children. Better empathy may also improve women's social network which may help in various ways with the caring of children. On the other hand, systemizing may help males become good hunters and increase their social status by improving spatial navigation and the making and use of tools.
Baron-Cohen argues that sex differences are not only due to socialization.
Extreme male brain theory of autism
Baron-Cohen's work in systemizing-empathisizing led him to investigate whether higher levels of fetal testosterone explain the increased prevalence of autism spectrum disorders among males in his theory is known as the "extreme male brain" theory of autism. A review of his book The Essential Difference (ISBN 978-0-7139-9671-5) published in Nature in 2003 summarizes his proposals as: "the male brain is programmed to systemize and the female brain to empathize ... Asperger's syndrome represents the extreme male brain".
Baron-Cohen and colleagues extended the E-S theory into the extreme male brain theory of autism, which hypothesizes that autism shows an extreme of the typical male profile. This theory divides people into five groups:
- Type E, whose empathy is at a significantly higher level than their systemizing (E>S).
- Type S, whose systemizing at a significantly higher level than their empathy (S>E).
- Type B (for balanced), whose empathy is at the same level as their systemizing (E=S).
- Extreme Type E, whose empathy is above average but whose systemizing is below average (E>>S).
- Extreme Type S, whose systemizing is above average but whose empathy is below average (S>>E).
Baron-Cohen says that tests of the E-S model show that twice as many females than males are Type E and twice as many males than females are Type S. 65% of people with autism spectrum conditions are Extreme Type S. The concept of the Extreme Type E brain has been proposed; however, little research has been conducted on this brain profile.
Apart from the research using EQ and SQ, several other similar tests also have found female and male differences and that people with autism or Asperger syndrome on average score similarly to but more extremely than the average male. For example, the brain differences model provides a broad overview of sex differences that are represented in individuals with autism, including brain structures and hormone levels.
Some, but not all studies, have found that brain regions that are different in average size between males and females also differ similarly between people who have autism and those who do not have autism.
Baron-Cohen's research on relatives of people with Asperger syndrome and autism found that their fathers and grandfathers are twice as likely to be engineers as the general population. Natural science students have more relatives with autism than humanities students. Another similar finding by Baron-Cohen in California has been referred to as the Silicon Valley phenomenon, where a large portion of the population works in technical fields, and he says autism prevalence rates are ten times higher than the average of the US population. These data suggest that genetics and the environment play a role in autism prevalence, and children with technically minded parents are therefore more likely to be diagnosed with autism.
Baron-Cohen's studies have been questioned. The overrepresentation of engineers could depend on a sampling bias, and a 2010 analysis of autism diagnoses in California did not find that autism clustered preferentially around areas rich in IT industry. Instead, it found that clusters tended to occur in areas where parents were older and educated to a higher level than were parents in surrounding areas.
Another possibility has been proposed that spins the perspective of the extreme male brain. Social theorists have been investigating the concept that females have protective factors against autism by having a more developed language repertoire and more empathy skills. Female children speak earlier and use language more than their male counterparts, and the lack of this skill translates into many symptoms of autism, offering another explanation for the discrepancy in prevalence.
Development of brain structures
The fetal testosterone theory hypothesizes that higher levels of testosterone in the amniotic fluid of mothers pushes brain development towards improved ability to see patterns and analyze complex systems while diminishing communication and empathy, emphasizing "male" traits over "female", or in E-S theory terminology, emphasizing "systemizing" over "empathizing".This theory states that fetal testosterone influences the development of certain structures in the brain, and that these changes relate to behavioral traits seen in those with autism. Males generally have higher levels of fetal testosterone contributing to their brain developing in that particular way. The extreme male brain theory (EMB), put forward by Baron-Cohen  suggests that autistic brains show an exaggeration of the features associated with male brains. These are mainly size and connectivity with males generally having a larger brain with more white matter, leading to increased connectivity in each hemisphere. This is seen in an exaggerated form in the brains of those with ASD. Another feature of male brains is having a smaller corpus callosum in at least some regions leading to decreased inter-hemispheric connectivity. This is also seen in those with ASD. Individuals with ASD were found to have widesperead interconnectivity abnormalities in specific brain regions. This could explain the different results on empathy tests between men and women  as well as the deficiencies in empathy seen in ASD as empathy requires several brain regions to be activated which need information from many different areas of the brain. A further example of how brain structure can influence ASD is looking at cases where the corpus callosum does not fully develop (agenesis of corpus callosum). It was found that autism is commonly diagnosed in children where the corpus callosum does not fully develop (45% of children with agenesis of the corpus callosum). A further example of brain structures relating to ASD is that children with ASD tend to have a larger amygdala, this is another example of being an extreme version of the male brain which generally has a larger amygdala. These brain differences have all been shown to have an influence on social cognition and communication. High levels of fetal testosterone have also been shown to be related to behavior associated with autism, such as eye contact. Studies examining the relationship between prenatal testosterone levels and autistic traits found that high levels correlated with traits such as decreased eye contact. These were present in both sexes. This suggests that fetal testosterone (fT) is the cause of sex differences in the brain and that there is a link between fT levels and ASD. In general females with autism have a higher rate of medical conditions which are related to high androgen levels and both males and females with autism have higher than average androgen levels. Males have higher fT levels naturally meaning that there is less of a change required in the hormone levels to reach a point high enough to cause the developmental changes seen in autism. This is a possible cause for the male prevalence seen in autism.
Imprinted brain theory
The imprinted brain theory is a somewhat similar although not identical theory. It argues that autism and psychosis are contrasting disorders on a number of variables. This is argued to be due to imbalanced genomic imprinting. According to the imprinted brain theory there could be a mismatch and more severe problems when extreme genomic imprinting occurs in the opposite sex, which would explain why female autism (and male psychosis) is often particularly severe, which is a problem for the "extreme male brain" theory which predicts the opposite.
Cognitive versus affective empathy
Empathy can been subdivided into two major components:
- cognitive empathy (also termed 'mentalizing'), the ability to understand another's mental state;
- affective or emotional empathy, the ability to emotionally respond to another's mental states. Affective empathy can be subdivided into personal distress (self-centered feelings of discomfort and anxiety in response to another's suffering) and empathic concern (sympathy towards others that are suffering).
Studies found that individuals with autism spectrum disorder (ASD) self-report lower levels of empathic concern, show less or absent comforting responses toward someone who is suffering, and report equal or higher levels of personal distress compared to controls. The combination of reduced empathic concern and increased personal distress may lead to the overall reduction of empathy in ASD.
Studies also suggest that individuals with ASD may have impaired theory of mind, involving the ability to understand the perspectives of others. The terms cognitive empathy and theory of mind are often used synonymously, but due to a lack of studies comparing theory of mind with types of empathy, it is unclear whether these are equivalent. Notably, many reports on the empathic deﬁcits of individuals with Asperger syndrome are actually based on impairments in theory of mind.
Baron-Cohen argued that psychopathy is associated with intact cognitive empathy but reduced affective empathy while ASD is associated with both reduced cognitive and affective empathy.
The theory has been criticized on multiple grounds. Some research in systemizing and empathizing in early life indicates that boys and girls develop in similar ways, casting considerable doubt on the theory of sex differences in these areas. A cognitive style that more naturally opposes empathizing is Machiavellianism, which emphasizes self-interest and which has been shown to be strongly correlated with competitiveness; evolutionary theory predicts that males will be more competitive than females. In contrast, research has generally shown a weak negative correlation between empathizing and systemizing.
Another criticism is that original EQ and SQ, which form most of the research basis behind the notions of empathizing and systemizing, both clearly measure more than one factor, and that sex differences exist on only some of the factors.
As a basis for his theory, Baron-Cohen cites a study done on newborn infants in which baby boys looked longer at an object and baby girls looked longer at a person. However, a review of studies done with very young children found no consistent differences between boys and girls.
Critics say that because his work has focused on higher-functioning individuals with autism spectrum disorders, his work requires independent replication with broader samples. A Nature article published in 2011 says, "Some critics are also rankled by Baron-Cohen's history of headline-grabbing theories—particularly one that autism is an 'extreme male' brain state. They worry that his theory about technically minded parents may be giving the public wrong ideas, including the impression that autism is linked to being a 'geek'."
Time magazine said Baron-Cohen "most dramatically wandered into fraught territory in 2003, when he published the book The Essential Difference, which called autism a manifestation of an extreme 'male brain'--one that's 'predominantly hard-wired for understanding and building systems,' as opposed to a 'female brain,' one that's 'predominantly hard-wired for empathy'--and ended up on the wrong side of the debate on science and sex differences." A book review published in the journal Nature, wrote:
"The idea that males are more interested in systemizing than females merits serious consideration ... It is unquestionably a novel and fascinating idea that seems likely to generate a rich empirical body of literature as its properties are tested. The second part of the theory—that females are more empathic than males—is more problematic."
Isabelle Rapin ... finds Dr. Baron-Cohen's theory "provocative" but adds that "it does not account for some of the many neurological features of the disorder, like the motor symptoms [such as repetitive movements and clumsiness], the sleep problems or the seizures." Others worry that the term "extreme male brain" could be misinterpreted. Males are commonly associated with "qualities such as aggression," says Helen Tager-Flusberg ... "What's dangerous is that's the inference people will make: Oh, these are extreme males."
Phenomenology and the Cognitive Sciences characterized The Essential Difference as "very disappointing" with a "superficial notion of intelligence", concluding that Baron-Cohen's major claims about mind-blindness and systemizing–empathizing are "at best, dubious". The Spectator says that "The emphasis on the ultra-maleness approach is no doubt attributable to the fact that Baron-Cohen works mainly with higher functioning autism and Asperger's syndrome."
- Baron-Cohen, S, Knickmeyer, R, & Belmonte, M (2005) Sex differences in the brain: implications for explaining autism. Science, 310, 819-823.
- Billington, J, Baron-Cohen, S, & Wheelwright, S, (2007) Cognitive style predicts entry into physical sciences and humanities: Questionnaire and performance tests of empathy and systemizing. Learning and Individual Differences, 17, 260-268.
- Simon Baron-Cohen (2009). "Autism: The Empathizing–Systemizing (E-S) Theory". Annals of the New York Academy of Sciences (New York Academy of Sciences) 1156 (The Year in Cognitive Neuroscience 2009): 68–80. doi:10.1111/j.1749-6632.2009.04467.x. PMID 19338503. Retrieved July 29, 2013.
- Nash A, Grossi G (2007). "Picking Barbie™'s brain: inherent sex differences in scientific ability?" (PDF). J Interdiscip Fem Thought 2 (1): 5.
- Andrew J, Cooke M, Muncer SJ (2008). "The relationship between empathy and Machiavellianism: an alternative to empathizing–systemizing theory". Pers Individ Dif 44 (5): 1203–11. doi:10.1016/j.paid.2007.11.014.
- Christopher Jarrold, David A. Routh (September 1998). "Is There Really a Link Between Engineering and Autism?". Autism 2 (3): 281–289. doi:10.1177/1362361398023006.
- Van Meter, K. C. et al. (2010) Geographic distribution of autism in California: a retrospective birth cohort analysis. Autism Res. 3, 19-29 easy to understand article
- Baron-Cohen S (2002). "The extreme male brain theory of autism". Trends Cogn Sci 6 (6): 248–254. doi:10.1016/S1364-6613(02)01904-6. PMID 12039606.
- Baron-Cohen S (2008). "Autism, hypersystemizing, and truth" (PDF). Q J Exp Psychol 61 (1): 64–75. doi:10.1080/17470210701508749. PMID 18038339. Retrieved 2009-06-09.
- Auyeung, B, Baron-Cohen, S, Wheelwright, S, Allison, C, Samarwickrema, N, Satcher, M, & Atkinson, M (2009) The Children’s Empathy Quotient and Systemizing Quotient: sex differences in typical development and in autism spectrum conditions. Journal of Autism and Developmental Disorders, 39, 1509-1521.
- Baron-Cohen, S, & Wheelwright, S, (2004) The Empathy Quotient (EQ). An investigation of adults with Asperger Syndrome or High Functioning Autism, and normal sex differences. Journal of Autism and Developmental Disorders, 34, 163-175.
- Golan, O, Baron-Cohen, S, & Hill, J, J, (2006) The Cambridge Mindreading (CAM) Face-Voice Battery: testing complex emotion recognition in adults with and without Asperger Syndrome. Journal of Autism and Developmental Disorders, 36, 169-183.
- Lawson J, Baron-Cohen S, Wheelwright S (2004). "Empathising and systemising in adults with and without Asperger Syndrome". J Autism Dev Disord 34 (3): 301–10. doi:10.1023/B:JADD.0000029552.42724.1b. PMID 15264498.
- Baron-Cohen, S., Lombardo, M. V., Auyeung, B., Ashwin, E., Chakrabarti, B., & Knickmeyer, R. (2011). "Why are autism spectrum conditions more prevalent in males?". PLoS Biology 9 (6). doi:10.1371/journal.pbio.1001081.
- Auyeung, B, Baron-Cohen, S, Chapman, E, Knickmeyer, R, Taylor, K & Hackett, G, (2006) Foetal testosterone and the Child Systemizing Quotient (SQ-C). European Journal of Endocrinology, 155, 123-130.
- Chapman, E, Baron-Cohen, S, Auyeung, B, Knickmeyer, R, Taylor, K & Hackett, G (2006) Foetal testosterone and empathy: evidence from the Empathy Quotient (EQ) and the ‘Reading the Mind in the Eyes’ Test’. Social Neuroscience, 1, 135-148.
- Knickmeyer, R, Baron-Cohen, S, Raggatt, P & Taylor, K (2006) Foetal testosterone and empathy. Hormones & Behaviour, 49, 282-292.
- Krieser, N. (2011) ASD in females: are we overstating the sex discrepancy in diagnosis. (Unpublished doctoral dissertation). Virginia Tech, Blacksburg, VA.
- Ingudomnukul, E., Baron-Cohen, S., Wheelwright, S., & Knickmeyer, R. (2007) Elevated rates of testosterone-related disorders in women with autism spectrum conditions. Hormones and Behavior, 51(5), 597-604. doi:10.1016/j.yhbeh.2007.02.001
- Knickmeyer, R. C., Baron-Cohen, S., Auyeung, B., & Ashwin, E. (2008) How to test the extreme male brain theory of autism in terms of foetal androgens? Journal of autism and developmental disorders, 38, 995-996.
- Baron-Cohen, S. (2005) Testing the extreme male brain (emb) theory of autism: let the data speak for themselves. Cognitive Neuropsychiatry , 10(1), 77-81.
- The Oxford Handbook of Evolutionary Psychology, Edited by Robin Dunbar and Louise Barret, Oxford University Press, 2007, Chapter 16 The evolution of empathizing and systemizing: assortative mating of two strong systemizers and the cause of autism, Simon Baron-Cohen.
- Baron-Cohen, Simon (2012-11-09). "Are geeky couples more likely to have kids with autism?". Scientific American. Retrieved 2013-12-28.
- Benenson JF (2003). "Sex on the brain". Nature 424 (6945): 132–133. doi:10.1038/424132b.
- Simon Baron-Cohen, Empathizing, systemizing, and the extreme male brain theory of autism. In: Ivanka Savic, editor, Sex Differences in the Human Brain, Their Underpinnings and Implications. Academic Press. 2010
- Simon Baron-Cohen, Sally Wheelwright, Carol Stott, Patrick Bolton, Ian Goodyer (July 1997). "Is There a Link between Engineering and Autism?". Autism 1 (1): 101–109. doi:10.1177/1362361397011010.
- Baron-Cohen, S. (2012, November). Autism and the technical mind. Scientific american, 307(5), 72-75.
- Luders, E., Toga, A.W., Thompson, P.M. (2014) Why size matters: Differences in brain volume account for apparent sex differences in callosal anatomy. The sexual dimorphism of the corpus callosum. NeuroImage, 84, 820-824
- Bruner, E., De La Cuetara, J. M., Colom, R., Martin-Loeches, M. (2012) Gender based differences in the shape of the human corpus callosum are associated with allometric variations. Journal of Anatomy, 220, 417-421
- Baron-Cohen, S., Knickmeyer, R. C., Belmonte, M. K. (2005) Sex differences in the brain: Implication for explaining autism, Science 310, 819-823.
- Fazier, T. W., Harden, A, Y. (2009) A Meta-Analysis of the Corpus Callosum in Autism, Biological Psychiatry, 66:10, 935-941.
- Anderson, J. S., T. Jason Druzgal, T. J., Alyson Froehlich, A., DuBray, M. B., Lange, N., Alexander, A. L.,Tracy Abildskov, T., Nielsen, J. A., Cariello, A. N., Cooperrider J. R., Bigler, E. D., Lainhart, J. E. (2011) Decreased Interhemispheric Functional Connectivity in Autism, Cerebral Cortex, 21 (5), 1134-1146
- Teatero, M. L., and Netley, C. (2013) A Criticall Review of the research on the extreme Male Brain Theory and digit Ratio (2D:4D). Journal of Autism and Developmental Disorders, 43, 11, 2664-2676.
- Lau, Y. C., Hinkley, L. B. N., Bukshpun, P., Strominger, Z. A., Wakahiro, M. L. J., Baron-Cohen, S., Allison, C., Auyeung, B., Jeremy, R, J., Nagarajan, S. S., Sherr, E. H., Marco, E. J. (2012) Autism traits in individuals with agenesis of the corpus callosum. J. Autism Dev. Disord. 42, 2312-2322
- Barnea-Goraly, N., Fazier, T. W., Piacenza, L., Minshew, N. J., Keshavan, M. S., Reiss, A. L., Hardan, A. Y., (2014) A preliminary longitudinal volumetric MRI study of amygdala and hippocampal volumes in autism, Progress in Neuro-Psychopharmacology and biological Psychiatry, 48:3, 124-128.
- Baron-Cohen, S., Lombardo, M. V., Auyeung, B., Ashwin, E., Chakrabarti, B., Knickmeyer, R. (2011) Why Are Autism Spectrum Conditions More Prevalent in Males? PLoS Biology, 9, 6.
- Auyeung, B., Ahluwalia, J., Thomson, L., Taylor, K., Hackett, G., O’Donnell, K. J., and Baron-Cohen, S. (2012) Prenatal versus postnatal sex steroid hormone effects on autistic traits in children at 18 to 24 months of age. Molecular Autism 3:17
- Lai, M. C., Lombardo, M.V., Suckling, J., Ruigrok,A. N. V., Chakrabarti, B., Ecker, C., Deoni, S. C. L., Craig, M. C., Murphy, D. G. M., Bullmore, E. T., and Baron-Cohen, S. (2013) Biological sex affects the neurobiology of autism. BRAIN: A Journal of Neurology, 1362799-2815.
- Badcock, C.; Crespi, B. (2008). "Battle of the sexes may set the brain". Nature 454 (7208): 1054–1055. doi:10.1038/4541054a. PMID 18756240.
- Ilaria Minio-Paluello, Michael V. Lombardo, Bhismadev Chakrabarti, Sally Wheelwright, Simon Baron-Cohen (2009). "Response to Smith's Letter to the Editor 'Emotional Empathy in Autism Spectrum Conditions: Weak, Intact, or Heightened?'" (PDF). J Autism Dev Disord 39 (12): 1749. doi:10.1007/s10803-009-0800-x.
- Lamm C., Batson C.D., Decety J. (2007). "The neural basis of human empathy: Effects of perspective-taking and cognitive appraisal". Journal of Cognitive Neuroscience 19 (1): 42–58. doi:10.1162/jocn.2007.19.1.42. PMID 17214562.
- Rogers K, Dziobek I, Hassenstab J, Wolf OT, Convit A (Apr 2007). "Who cares? Revisiting empathy in Asperger syndrome" (PDF). J Autism Dev Disord 37 (4): 709–15. doi:10.1007/s10803-006-0197-8. PMID 16906462.
- Gillberg, C. L. (1992). The Emanuel Miller Memorial Lecture 1991. Autism and autistic-like conditions: subclasses among disorders of empathy. Journal of Child Psychology and Psychiatry, and Allied Disciplines, 33(5), 813–842.
- Roeyers, H., Buysse, A., Ponnet, K., & Pichal, B. (2001). Advancing advanced mind-reading tests: empathic accuracy in adults with a pervasive developmental disorder. Journal of Child Psychology and Psychiatry, and Allied Disciplines, 42(2), 271–278.
- Baron-Cohen, Simon (2011). Zero Degrees of Empathy: A New Theory of Human Cruelty. Penguin UK. Retrieved August 8, 2013.
- Elizabeth S. Spelke (2005). "Sex Differences in Intrinsic Aptitude for Mathematics and Science? A Critical Review" (PDF). American Psychologist 60 (9): 950–958. doi:10.1037/0003-066X.60.9.950. PMID 16366817.
- Alice S. Carter, David O. Black, Sonia Tewani, Christine E. Connolly, Mary Beth Kadlec, Helen Tager-Flusberg (2007). "Sex Differences in Toddlers with Autism Spectrum Disorders" (PDF). J Autism Dev Disord 37 (1): 86–97. doi:10.1007/s10803-006-0331-7.
- Buchen L (November 2011). "Scientists and autism: When geeks meet". Nature 479 (7371): 25–7. doi:10.1038/479025a. PMID 22051657.
- Warner, Judith (2011-08-29). "Autism's lone wolf". Time. Retrieved 2013-12-28.
- McGough, Robert (16 July 2003). "Is the autistic brain too masculine?". Wall Street Journal. p. B1.
- Levy, Neil (2004). "Book review: Understanding blindness". Phenomenology and the cognitive sciences 3 (3): 315–24. doi:10.1023/B:PHEN.0000049328.20506.a1. (subscription required (. ))
- Lawson-Tancred, Hugh (2003-06-14). "What little boys and girls are made of". p. 67. Retrieved 2013-12-29.
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- Online version of the EQ test
- Baron-Cohen, Simon — The Male Condition The New-York Times, 8 August 2005
- Baron-Cohen, Simon — They just can't help it The Guardian, 17 April 2003
- Kunzig, Robert — Autism: What's Sex Got to Do with It? Psychology Today, 1 January 2004