Autism is defined as an abnormal absorption in self-centred subjective mental activity (as in day-dreams and hallucinations). Autism is a mental condition usually present from childhood. It is characterized by complete self-absorption and reduced ability to respond to or communicate with the outside world.

Autism may be interpreted as "mind blindedness". It is actually an impairment of central coherence. Central coherence describes that characteristic of normal human information processing which tends to draw together diverse bits of information to construct higher level meaning in context. In autistic children, there appears to be a specific imbalance in information-processing, especially in the filtering and prioritization of data at both perceptual and cognitive levels.

Autism can occur in ranges from "severely affected" to "mildly affected". Autism is a developmental diagnosis, i.e., it is apparent only as and when the child suffers delay in normal development.