In this chapter, we provide an overview of past and current research on developmental phonetics. We situate our work within the body of literature on child language phonetics and phonology, which describes speech production patterns, often in the context of other aspects (e.g. phonological, lexical) of the child’s larger linguistic system. Research on phonetic development poses unique challenges, in particular concerning the modelling of the child’s constantly evolving linguistic abilities, which take place in the context of other aspects of the child’s development. We discuss areas of interaction between phonology and other aspects of children’s linguistic behaviours, including how issues affecting speech articulation may influence the emergence of phonological processes, covert contrasts in production, and individual patterns of lexical selection and avoidance. Throughout this discussion, we review methodological approaches to developmental phonetics, from traditional, corpus-based investigations to more recent developments in instrumental studies of child speech, and discuss their contributions to our understanding of phonetic and phonological development in child language.

The observation and measurement of the movement of the organs of the vocal tract during speech is relevant for the understanding of phonetic phenomena, from descriptions of under-documented languages and cross-linguistic comparison of speech sound production, to investigations of factors impacting speech motor planning, and to testing models of the relationship between the vocal tract and acoustics. This chapter describes the most commonly used methods for measuring or recording the position and movements of the organs that make up the vocal tract during speech. Techniques discussed in this chapter include direct vocal tract imaging (e.g. magnetic resonance imaging (MRI), laryngoscopy, ultrasound imaging), articulatory point tracking (e.g. X-ray microbeam tracking (XRMB), electromagnetic articulography (EMA), Velotrace), and indirect measures of articulator movement (e.g. electroglottography (EGG), airflow and air pressure measures, static palatography and electropalatography (EPG)). These methods vary in a number of respects. This chapter discusses advantages and drawbacks of each method described, as well as factors relevant to researchers during the planning stages of a study.