The Research Focus "Language: Birth and Decay" is concerned with how the sounds of speech are acquired by infants and young children in first language acquisition, how such acquisition stabilizes in healthy individuals, and how such patterns may dissolve following the onset of brain lesions. Spoken language is a defining human behaviour, and it is the very basis of our interaction with the environment as well as of our identity as individuals. For this reason, it is important to understand both how this faculty emerges during child development and the highly damaging effect that speech disorders have on so many aspects of life. Error patterns when language is learnt and when it unravels in speech disorders also provide a unique window to the mind, and are of prime importance for our emerging understanding of how linguistic diversity arises, how languages change, and how physiology and cognition interact to form the sound patterns of human language. Yet speech acquisition and disorders remain poorly understood because they are usually investigated separately from basic research on speech production and perception in healthy individuals. One of the Research Focus’ principal objectives is to overcome this divide by inviting leading scientists from different disciplinary backgrounds to consider how to develop unified models of child speech acquisition, of the mature speech production and perception system, and of speech disorders. The involved researchers intend to lay the foundations for a comprehensive research program in which modern experimental phonetic thinking hooks up with neurobiological and clinical reasoning, while embracing linguistic diversity.