20th International Congress on Acoustics 2010, ICA 2010 - Incorporating the 2010 Annual Conference of the Australian Acoustical Society, Sydney, Australia, 23 - 27 August 2010, vol.5, pp.3709-3718
To understand the now well-established auditory-visual nature of speech perception, it is necessary to understand how it develops. We know that young infants perceive speech auditory-visually by the fact that they perceive the auditory-visual illusion known as the McGurk effect; that visual information use increases over age in Englishlanguage children; and that Japanese-language adults use less visual information than do their English-language counterparts. Here we complete the developmental scene and probe the processes involved. In Experiment, with 6-, 8-, and 11-year-old and adult Japanese- and English-language participants tested on a McGurk task, while 6-year-olds from both language groups were equivalently influenced by visual speech information, there was a significant jump in auditory-visual speech perception between 6 and 8 years in English- but not Japanese-language participants. To investigate this further, in Experiment 2 we gave English-speaking 5-, 6-, 7- and 8-year-olds and adults a McGurk effect task as well as a language-specific speech perception (LSPP) test with native- and non-native speech sounds, and reading and articulation tests. For children, but not adults, visual-only speech perception (lipreading) ability and LSSP predicted McGurk performance - children with good auditory-visual speech perception tended to be those who focussed more on native than non-native speech sounds. In Experiment 3, with 3- and 4-year-olds tested for McGurk effect, LSSP, receptive vocabulary, and cognitive skill, regression analyses showed that auditory-only speech perception and cognitive skill, but not LSSP, predicted auditory-visual speech performance. Together the results show that there is an increase in auditory-visual speech perception between 6 and 8 years in English- but not Japanese-language children, and in English-language children this is related to language specific speech perception processes specifically around that age (5, 6, 7, 8 years) and not before (3, 4 years) or after (adults). It is suggested that LSSP is most variable and most predictive of visual influence in speech perception in the presence of significant linguistic challenges, such as those at the onset of reading instruction.