In essence, autism affects the way a person interacts socially. Autism may appear from birth or from infancy, and causes difficulty in developing normal social relationships, and in normal communication.

It must be stressed that autism is a condition with a wide-ranging degree of severity. Two individuals with autism may share the characteristic triad of impairments (as discussed below), yet differ in overall level of functioning. This is due to factors such as additional mental handicaps, language ability, age, etc. Because of this varying range of abilities, the condition is often referred to as the Autistic Spectrum Disorder (ASD), Individuals on the higher end of the spectrum are relatively able, and are said to have Asperger Syndrome.

What are the characteristics of ASD?

Individuals with ASD look no different from other people, leading to autism being sometimes called the "invisible disability". However, understanding of their unique condition will prevent unfair judgement of their behaviour.

Lorna Wing’s "Autistic Spectrum Disorders: an aid to diagnosis", lists the following essential features.

(It is necessary to note that ALL the following three key types of behaviour must be present, before a diagnosis of autism can be made.)

The Triad of Impairments: -

1. Impairment of social interaction
   …difficulty in relating to others
2. Impairment of social communication
   …poor use and understanding of language
3. Impairment of imagination
   …inability to play imaginatively with toys or interact socially due to lack of intuition and common sense
   [NB: ‘common sense’ refers to a set of background assumptions held by all members of a community. Individuals with ASD generally do not share in this and thus tend to understand things very literally.]

In addition, frequent engagement in
4. Repetitive stereotyped activities