Final Report Summary - NEURODEVELOPMENT (A neurodevelopmental approach to human language processing)
Our research has shown that adults process different aspects of the speech signal by independently operating subroutines. Parallel processing helps adult listeners, for example, to recognize mispronounced words such as 'shigarette' as a variant of 'cigarette'. Some subroutines of speech processing tolerate this variation while others do not. After having established parallel operating subroutines in adults, we followed their development in early ontogeny. Our findings reveal individual developmental trajectories for different aspects of speech processing. For example, infants focus on speech sound details three months after birth, but are more tolerant to subtle speech variation six months after birth. Nine months after birth, infants show evidence for both precise and rough speech processing strategies. Thus, the parallel architecture that characterizes adult speech processing appears to be established already at the end of the first year of life. Sequential shaping of separate subsystems and parallel processing nine months after birth also became evident for the processing of prosody-relevant and phoneme-relevant aspects of speech. Our results make it clear (i) that cognitive development obeys fine-grained trajectories within infancy; (ii) that after sequential shaping of independent aspects of the complex speech processing stream, parallel processing is established at the end of infancy; and (iii) that combined infant data from several age groups are essentially needed four understanding this rapid development in early language acquisition.