Private Speech and Inner Speech in Typical and Atypical Development

Children often talk themselves through their activities: They produce private speech to regulate their thought and behaviour, which is internalised to form inner speech, or silent verbal thought. Private speech and inner speech can together be referred to as self-directed speech (SDS). SDS is thought to be an important aspect of human cognition. The first chapter of the present thesis explores the theoretical background of research on SDS, and brings the reader up-to-date with current debates in this research area. Chapter 2 consists of empirical work that used the observation of private speech in combination with the dual task paradigm to assess the extent to which the executive function of planning is reliant on SDS in typically developing 7- to 11-year-olds. Chapters 3 and 4 describe studies investigating the SDS of two groups of atypically developing children who show risk factors for SDS impairment—those with autism and those with specific language impairment. The research reported in Chapter 5 tests an important tenet of neoVygotskian theory—that the development of SDS development is domain-general—by looking at cross-task correlations between measures of private speech production in typically developing children. Other psychometric properties of private speech production (longitudinal stability and cross-context consistency) were also investigated. Chapter 6, the General Discussion, first summarises the main body of the thesis, and then goes on to discuss next steps for this research area, in terms of the methods used to study SDS, the issue of domain-general development, and the investigation of SDS in developmental disorders.