The purpose of this study was to examine age- and hearing-related differences in school-age children’s benefit from visual speech cues. The study addressed three questions: (1) Do age and hearing loss affect degree of audiovisual (AV) speech enhancement in school-age children? (2) Are there age- and hearing-related differences in the mechanisms underlying AV speech enhancement in school-age children? (3) What cognitive and linguistic variables predict individual differences in AV benefit among school-age children?
Forty-eight children between 6 and 13 years of age (19 with mild to severe sensorineural hearing loss; 29 with normal hearing) and 14 adults with normal hearing completed measures of auditory and AV syllable detection and/or sentence recognition in a two-talker masker type and a spectrally matched noise. Children also completed standardized behavioral measures of receptive vocabulary, visuospatial working memory, and executive attention. Mixed linear modeling was used to examine effects of modality, listener group, and masker on sentence recognition accuracy and syllable detection thresholds. Pearson correlations were used to examine the relationship between individual differences in children’s AV enhancement (AV−auditory-only) and age, vocabulary, working memory, executive attention, and degree of hearing loss.
Significant AV enhancement was observed across all tasks, masker types, and listener groups. AV enhancement of sentence recognition was similar across maskers, but children with normal hearing exhibited less AV enhancement of sentence recognition than adults with normal hearing and children with hearing loss. AV enhancement of syllable detection was greater in the two-talker masker than the noise masker, but did not vary significantly across listener groups. Degree of hearing loss positively correlated with individual differences in AV benefit on the sentence recognition task in noise, but not on the detection task. None of the cognitive and linguistic variables correlated with individual differences in AV enhancement of syllable detection or sentence recognition.
Although AV benefit to syllable detection results from the use of visual speech to increase temporal expectancy, AV benefit to sentence recognition requires that an observer extracts phonetic information from the visual speech signal. The findings from this study suggest that all listener groups were equally good at using temporal cues in visual speech to detect auditory speech, but that adults with normal hearing and children with hearing loss were better than children with normal hearing at extracting phonetic information from the visual signal and/or using visual speech information to access phonetic/lexical representations in long-term memory. These results suggest that standard, auditory-only clinical speech recognition measures likely underestimate real-world speech recognition skills of children with mild to severe hearing loss.