The diagnostic criteria for autism have been refined and made more objective since Kanner first described the syndrome, so there is now reasonable consistency in how this diagnosis is applied. However, many children do not meet these criteria, yet show some of the features of autism. Where language development is impaired, such children tend to be classed as cases of developmental dysphasia (or specific language impairment) whereas those who learn to talk at the normal age may be diagnosed as having Asperger's syndrome. It is argued that rather than thinking in terms of rigid diagnostic categories, we should recognise that the core syndrome of autism shades into other milder forms of disorder in which language or non-verbal behaviour may be disproportionately impaired.