The effects of prematurity and socioeconomic deprivation on early speech perception: A story of two different delays

There is evidence showing that both maturational and environmental factors can impact on later language development. On the one hand, preterm birth has been found to increase the risk of deficits in the preschool and school years. Preterm children show poorer auditory discrimination, reading difficulties, poor vocabulary, less complex expressive language and lower receptive understanding than their matched controls. On the other hand, socioeconomic status (SES) indicators (i.e., income, education and occupation) have been found to be strongly related to linguistic abilities during the preschool and school years. However, there is very little information about how these factors result in lower linguistic abilities. The present study addresses this issue. To do so, we investigated early speech perception in full and preterm infants from families classed as high or low SES. Seventy-six infants were followed longitudinally at 7.5, 9, 10.5 and 12 months of age. At each test point, three studies explored infants' phonetic, prosodic and phonotactic development respectively. Results showed no significant differences between the phonetic or the phonotactic development of the preterm and the full-term infants. However, a time-lag between preterm and full-term developmental timing for prosody was found. Socioeconomic status did not have a significant effect on prosodic development. Nonetheless, phonetic and phonotactic development was affected by SES, infants from lower SES showed phonetic discrimination of non-native contrast and a preference for high-probability sequences later than their more advantaged peers. Overall these results suggest that different constraints apply to the acquisition of different phonological subcomponents.