Poverty, prematurity, and the role of auditory functions in language acquisition

The auditory system undergoes considerable development through adolescence. In the meantime, children need to acquire spoken language. We explored the idea that emerging auditory functions can constrain language development, if those functions are delayed. Hypotheses were: (1) language skills most reliant on auditory functions are most affected by delays in auditory development; and (2) childhood conditions known to affect language development actually take their toll through delays in auditory development. We tested 120 five-to-six-year-olds varying in socioeconomic status, gestational age at birth, and number of ear infections, all conditions known to impact language development. Measures included auditory functions (temporal and spectral modulation sensitivity), lexicosyntactic skill (vocabulary and auditory comprehension), and phonological sensitivity (rhyme oddity and consonant matching). Results supported H1, auditory functions were strongly correlated with language skills, especially phonological sensitivity, and H2, socioeconomic status and gestational age were correlated with auditory functions. Socioeconomic status was found to exert independent environmental and auditory sources of effect, but premature birth impacted language development entirely through its impact on auditory development. These findings suggest that physiological models of developmental language delay, rather than purely environmental models, need to be explored. Reasons why ear infections had less effect will be discussed.