Autism is a pervasive developmental disorder characterised by restricted and repetitive behaviour and impaired social interaction and communication.


  • 1% of children
  • .1% worldwide
  • Diagnoses have increased since the 1980s due to diagnostic changes, but actual prevalence may not have increased, or may have always been this high


  • Markedly impaired social interaction and communication
    • Impairment in non-verbal behaviours (looking at eyes)
    • Delay or failure to develop verbal language
    • Impaired ability to initiate or sustain a conversation
    • Poor social skills; e.g. white lies
  • Restricted and stereotyped behaviour and interests
    • Encompassing preoccupation with a few specific interests (e.g. minesweeper)
    • Inflexible adherence to routines
    • Hand-flapping, rocking, etc

Autism Experiments

Eye-Gaze Tracking

Klin et al 2002 played movies to a mix of autistic and non-autistic individuals and tracked their eye-gaze. They found that healthy individuals tracked social aspects of the scene, whilst autistic individuals tracked non-social aspects.




Baron-Cohen et al, 1985, came up with the hypothesis that autistic individuals cannot represent the mental states of other people. They used an experiment involving hidden knowledge to show this:


Healthy children and Down's children both suggest that Sally will look for the ball in the basket (85% of them), whereas autistic children suggest Sally will look for the ball in the box (80% of them).

Weak Central Coherence Hypothesis

The Weak Central Coherence Theory suggests that a cognitive style that can perceive parts but not the whole.