New Theories of Autism: Hyper-Systemizing and Assortative Mating

Simon Baron-Cohen, PhD, MPhil


December 29, 2005

In This Article

The Assortative Mating of High Systemizers

The evidence for systemizing being part of the phenotype for ASC includes the following: fathers and grandfathers of children with ASC are twice as likely to work in the engineering field (a clear example of a systemizing occupation) compared with men in the general population.[37] Thus, these fathers and grandfathers may have a higher-than-average SM (level 4). Students in the natural sciences (engineering, mathematics, physics) have more relatives with autism than do students in the humanities.[38] Mathematicians have a higher rate of AS compared with the general population, and so do their siblings.[39]

The evidence that autism could be the genetic result of having 2 high systemizers as parents (assortative mating) includes the following:

  • Both mothers and fathers of children with AS have been found to be strong in systemizing on the Embedded Figures Test[21];

  • Both mothers and fathers of children with autism or AS have higher rates of systemizing occupations among their fathers[37]; and

  • Both mothers and fathers of children with autism show hyper-masculinized patterns of brain activity during a systemizing task[40];

Whether the current high rates of ASC simply reflect better recognition, growth of services, and widening of diagnostic categories to include AS, or also reflect the likelihood that 2 high-systemizers will have children, is a question for future research.

The core of ASC comprises both a social deficit and what Kanner astutely observed as, and aptly named, "need for sameness."[4] According to the hyper-systemizing theory, ASC results from a normative SM (the function of which is to serve as a change-predicting mechanism) being set too high. This theory explains why people with autism prefer no change, or appear "change-resistant." It also explains their preference for systems that change in highly lawful or predictable ways (such as mathematics, repetition, objects that spin, routine, music, machines, collections). Finally, it also explains why they become disabled when faced with systems characterized by "complex" or less lawful change (such as social behavior, conversation, people's emotions, or fiction), since these cannot be easily systemized.

Although ASCs are disabling in the social world, hyper-systemizing can result in abilities in areas that are systemizable. For many people with ASC, hyper-systemizing never moves beyond phase 1, the massive collection of facts and observations (eg, lists of trains and their departure times, watching the spin-cycle of a washing machine), or phases 2 and 3, massive repetition of behavior (eg, spinning a plate or the wheels of a toy car). But for those who go beyond phase 3 to identify a law or a pattern in the data (phases 4 and 5), this can constitute original insight. In this sense, it is likely that the genes for increased systemizing have made remarkable contributions to human history.[41,42,43]


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