EDITOR—Lloyd and Brodie propose that the ability of an 18 month old child to recognise television images may be a useful milestone in the assessment of development.1 Their data derive from the examination of two conditions only: Down's syndrome and normality. To extend the concept to include learning disabilities in general, language disorders, and autism is not necessarily valid.

The authors found that their milestone had a high degree of specificity (96%): very few normal children were unable to recognise television images. …