When are speech sounds learned and why is this important for children to be heard?

Children’s communication development is a remarkable achievement that enables children to realise their right to receive information and express their views freely (United Nations, 1989). Until recently, limited information has been available about communication expectations for children, especially in languages other than English. In this chapter, we draw together and elaborate on three large-scale reviews of children’s consonant and intelligibility development across more than 30 languages encompassing data from thousands of children worldwide. Understanding the developmental trajectory of children’s communication enables us to recognise when children have difficulties, which can lead to children’s voices being misinterpreted or silenced. Our analysis concludes that across the world, almost all 4- to 5-year-old children are intelligible to family members, friends, and strangers, have acquired most consonants within their ambient language, and can produce consonants correctly more than 90% of the time. By understanding children’s developmental trajectory for communication, parents, educators, and health professionals can advocate for and make timely referrals to communication specialists (e.g. speech-language pathologists) who can support the development of communication, improve participation of children, and reduce inequalities (SDG 10), including the impact of communication difficulties on literacy, numeracy, socialisation, behaviour, and inclusion.