The empathizing–systemizing (E-S) theory classifies people on the basis of their scores along two dimensions: empathizing (E) and systemizing (S). It measures a person's strength of interest in empathy (defined as the drive to identify a person's thoughts and feelings and to respond to these with an appropriate emotion); and a person's strength of interest in systems (defined as the drive to analyse or construct a system). A system in turn is defined as anything that follows rules, key classes of systems including mechanical systems, natural systems, abstract systems, and collectible systems. Rules in turn are defined as repeating, lawful patterns.
The E-S theory has been tested using the Empathy Quotient (EQ) and Systemizing Quotient (SQ), and generates 5 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). The E-S theory is a better predictor of who goes into STEM (Science, Technology, Engineering and Mathematics) subjects than is gender. The E-S theory has been extended into the 'Extreme Male Brain' (EMB) theory of autism who show deficits and delays in cognitive empathy (also called 'theory of mind') alongside intact or superior systemizing.
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 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. 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.
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.
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'. People with autism and Asperger syndrome show significantly lower scores on these same measures of empathy and either intact or even significantly higher scores on these measures of systemizing.
Fetal testosterone 
Whilst experience and socialization contribute to the observed sex differences in empathy and systemizing, biology is also suggested to play a role and a candidate biological factor influencing E and S is fetal testosterone (FT) (PLOS Biology, 2011). 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. Overall, 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. For example, better empathizing may improve care of children. Better empathy may also improve women's social network which may help in various way 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.
Research on one-day-old babies has found that boys look longer at a mechanical mobile while girls look longer at a face. This, as well as the effects of fetal testosterone on later behavior, is argued to be evidence against the sex differences being only due to socialization.
The extreme male brain theory of autism 
The E-S theory was extended 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).
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.
Research on relatives of people with Asperger syndrome and autism has 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 in California has been referred to as the “Silicon Valley phenomenon”, where a large portion of the population works in technical fields, and autism prevalence rates are ten times higher than the average of the US population. These correlational 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.
However, these 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.
Asperger syndrome is found more often in mathematicians and their siblings than in the general population. Both mothers and fathers of children with Asperger syndrome tend to score high on systemizing. Both mothers and fathers of children with autism or Asperger syndrome often have father who worked in systemizing occupations. Both mothers and fathers of children with autism have a strongly masculine pattern of brain activity when doing systemizing activity.
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.
The extreme male brain theory explores the biological and social explanations for sex differences in autism.
Assortative mating 
Diagnosed autism has greatly increased. This may be due to factors such as better awareness or changed criteria for diagnosis. Another possibility is that reduced barriers between people have increased assortative mating, including for high systemizers, which would increase the likelihood of a child developing autism.
Cognitive versus affective empathy 
Empathy can been subdivided into two major components:
- cognitive empathy (also termed 'theory of mind' or 'mentalizing') defined as the drive to identify another's mental states;
- affective empathy, defined as the drive to respond with an appropriate emotion to another's mental states.
Whilst numerous studies have reported difficulties in cognitive empathy in autism and Asperger syndrome, affective empathy may be intact in people with these diagnoses. That is, individuals with autism have difficulties ascertaining others' thoughts and feelings, but experience empathy when they are aware of others' states of mind.
Baron-Cohen argued that autistic persons and psychopaths are mirror opposites. Psychopaths show intact cognitive empathy but impaired affective empathy whilst people with autism show impaired cognitive empathy but intact affective empathy. He argues that this is why psychopaths can go on to commit acts of cruelty and why acts of cruelty are uncommon in autism. People with autism struggle to understand other people's motives, intentions and behaviour and tend to avoid relationships, finding them confusing, but rarely hurt others. In contrast, psychopaths tend to manipulate others by using their intact cognitive empathy and often hurt others.
The theory has inevitably become involved in the debate over the origin of cognitive and behavioural sex differences. One contrasting view is that all such sex differences can be explained purely in terms of nurture and upbringing. The E-S theory in contrast does not discount the importance of nurture and experience but argues that over and above such environmental influences, biology also plays a role. And the theory only makes claims about group differences on average. That means that an individual male or female may not be typical for their sex. The E-S theory argues it does not stereotype since the implication of the theory is that one cannot prejudge an individual based on their sex, in the absence of knowing their E-S 'brain type'.
The theory has also been criticized on 4 grounds about the link to autism:
- It is argued that people with autism do have empathy because they can be caring towards others in distress. This criticism is based on a misunderstanding of the E-S theory because the theory argues that affective empathy is intact in autism and it is only cognitive empathy that is impaired in autism.
- It is argued that the idea that people with autism are intact or superior in systemizing does not always hold, on the grounds that they may not always show strengths in subjects such as mathematics. Again, this is a misunderstanding of the E-S theory because the theory does not suggest intact or superior strengths in understanding all or every system. The E-S theory simply holds that the size of the discrepancy between E and S (S>>E) is on average greater in autism than in others in the population. In addition, since the nature of systemizing is that one focuses on a specific system, one person with autism may thus develop a strong narrow focus on a highly specific mathematical system such as Pi, or taking apart and reassembling a mechanical system such as a bicycle. Another may focus on just on compiling elaborate taxonomic lists to determine the sequence of their DVDs on a bookshelf, or on memorizing railway timetables. These differences only hold on average, since an individual person with autism may not be typical for their diagnostic group.
- Whilst strong systemizing may characterize 'obsessions' in Asperger syndrome, it may not apply to classic autism who may have additional learning difficulties. Testing systemizing in the latter subgroup is more challenging but Baron-Cohen has suggested that the extreme repetitive behaviour seen even in those with autism and learning difficulties (such as spending hours bouncing on a trampoline, or repeating phrases with exact intonation, or scrutinizing spinning wheels on a toy car, or lining up coloured bricks in exact sequences and becoming distressed if anyone disrupts these) reflects their strong interest in repeating patterns (or lawful regularities) which define a system.
- People with autism may not match the description of being 'extreme males' because they are not more aggressive or more physically masculine than others. Again, this misunderstands the 'extreme male brain' theory which does not argue that people with autism show an extreme of all male traits (such as height, aggression, visuospatial skills, or muscularity) but only on E-S measures: below average cognitive empathy and intact or above average systemizing.
To date there are still too few studies of women with Asperger syndrome (AS) but a recent cognitive study confirms this profile. Women with AS show elevated levels of a precursor of testosterone (androstenedione) and show a different protein profile in relation to sex hormones.
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.
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|Look up systemize in Wiktionary, the free dictionary.|
- EQ SQ website
- 'They just can't help it', Simon Baron-Cohen, The Guardian (April 17, 2003)
- 'Autism: What's Sex got to do With it?', Robert Kunzig, Psychology Today (January/February 2004)