A prediction about the results of an experiment, based on previous theory and findings concerning the phenomena that the experiment is designed to investigate. The hypothesis is formed before the experiment takes place.

A term used for the insights contributed by people with autism based on their own experience of the condition.

The overall score that a person achieves on a standardised test of verbal and non-verbal abilities, which indicates how well they perform in comparison to others of the same age.

The World Health Organisation's formal system for the classification and diagnosis of physical, psychiatric, mental health and developmental conditions. The current edition (ICD-10) reflects the older sub-type approach to diagnosing autism, whereas the next edition (ICD-11) due in 2018 will be more aligned with the DSM-5 approach.

The group in a controlled intervention evaluation study who receives the intervention. (See also Randomised Control Trial, Controlled Study.)

Procedures for supporting and improving the development, functioning and well-being of someone with autism, helping them to engage with others, thrive and fulfil their potential.

The characteristic rise and fall of speech, which plays a role in communication. People with autism may have difficulty interpreting intonation in speech, or may have unusual intonation themselves. (See also non-verbal communication.)

The phenomenon in which one person coordinates or shares their attention with another, in order to focus on the same object or event. Joint attention emerges in typically developing children by about 12 months of age. Children later receiving autism spectrum diagnoses often show poor joint attention skills.

A term sometimes used for the form of autism with profound social and communication difficulties often including little or no speech, markedly restricted and repetitive behaviour and interests, and intellectual disabilities.

A study which follows the same participants over a substantial period of time – usually several years.