Language processing supporting cognitive performance: an investigation of children’s and adults’ inner speech using behavioral, electrophysiological and optical methods

Inner speech has been implicated in Vygotsky´s theory of cognitive development. Converging evidence suggests that language skills as well as self-directed speech, in particular inner speech, is important for cognitive functions. However, the role of self-directed speech (including inner speech) in the relation between language skills and cognition have remained unclear. Despite a growing body of studies on the neural substrate of inner and overt speech, evidences of the neural differences between inner and overt speech have remained diffuse. The present dissertation aimed at filling the gap by investigating inner speech and its process of internalization with behavioral and neuroscientific methods. One study addressed the role of self-directed speech in the interplay between language skills and cognition by using the Tower of London task in children. Two studies addressed the neural correlates of the differences between inner and overt speech in adults and children during a picture-naming task by simultaneously applying the electroencephalography and functional near-infrared spectroscopy. The results of the first study confirmed that the internalization of speech is related to children´s cognition although it cannot explain the relation between language skills and problem-solving. The second study showed that inner speech is not overt speech without articulation, even more it is that prior phonological processes are downregulated. Moreover, the study showed that the brain differentiates between inner and overt speech even when no linguistic and motoric process is necessary. The results of the third study showed less differences between inner and overt speech in children indicating that inner speech is not yet adult-like. Even more it seems that inner speech represents linguistically the same like overt speech in the children´s brain.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Universität Leipzig

Year

2020

Author dc:creator

• Stephan, Franziska

• inner speech
• problem-solving
• Vygotsky
• electroencephalography
• near-infrared spectroscopy