Unclear speech: recognition and significance of unintelligible speech in preschool children.

Clarity of speech normally improves throughout the first few years of life, with acquisition of complete intelligibility by 4 years of age. Delayed emergence of intelligibility, or frankly unintelligible speech, often signify the presence of a major disturbance of language, overall cognitive development, or hearing. Norms are provided for the ages by which a child should be 50%, 75%, and 100% intelligible to strangers, and a new technique for screening intelligibility of speech is described. Data validating this technique are presented, and the developmental implications of unintelligible speech are reported. The importance of screening for intelligibility of speech is emphasized, in light of the findings presented.