Autism is diagnosed when a child or adult has abnormalities in a “triad” of behavioural domains: social development, communication, and repetitive behaviour/obsessive interests.^1,2 Autism can occur at any point on the IQ continuum, and IQ is a strong predictor of outcome.³ Autism is also invariably accompanied by language delay (no single words before 2 years old). Asperger syndrome (AS)⁴ is a subgroup on the autistic spectrum. People with AS share many of the same features as are seen in autism, but with no history of language delay and with an IQ in the average range or above. In this editorial, the main cognitive theories of autism are summarised. These are then followed by a summary of the key neurobiological findings.

AUTISM: COGNITIVE ASPECTS

The mind blindness theory of autism⁵ proposed that in autism spectrum conditions there are deficits in the normal process of empathy, relative to mental age. These deficits can occur by degrees. The term “empathising” encompasses a range of other terms: “theory of mind”, “mind reading”, “empathy”, and taking the “intentional stance”.⁶ Empathy involves two major elements: (1) the ability to attribute mental states to oneself and others, as a natural way to make sense of agents,^7–9 and (2) having an emotional reaction that is appropriate to the other person’s mental state (such as sympathy).

Since the first test of mind blindness in children with autism,¹⁰ there have been more than 30 experimental tests. The vast majority of these have revealed profound impairments in the development of their empathising ability. These are reviewed elsewhere.^5,11 Some children and adults with AS only show their empathising deficits on age appropriate adult tests.^12–14 This deficit in their empathising is thought to underlie …