Prevalence of around 0.9%, but more in males than females. Polygenic (high heritability). Wing (1988) characterised Autism as a triad of impairments: social deficit, communicative deficit, and repetitive and stereotyped behaviours.
Theory of mind account: Baron-Cohen, Leslie & Frith (1985) found that ASD children were pretty bad at a variant of Wimmer and Perner's false belief task (80% failed), compared with 4 year old children and mental age-matched children with Down's syndrome (86% passed). Precursors to theory of mind are observable in infants (Onishi & Baillargeon, 2005) and toddlers. There is an absence of theory of mind in children autism.
Happe et al (2006): maybe there is no core deficit - symptoms of ASD can be pretty unrelated to each other, with poor correlations between different symptoms. Twin data suggests the various symptoms are coded by different genes.
Not all children who show atypical markers go on to develop ASD (Elsabbagh & Johnson, 2010). Risk of ASD is associated with the way the brain responds to dynamic stimuli.
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