Hay, J. 1 , Robertson, V. S. 2 & von Hapsburg, D. 2
1 Department of Psychology, University of Tennessee
2 Department of Audiology & Speech Pathology, University of Tennessee, Health Science Center
Infant-directed speech (IDS) is an exaggerated form of speech caregivers use with infants. It has higher pitch, longer duration, an enlarged vowel space, and is more rhythmic than adult-directed speech (ADS). IDS is thought to capture infant attention, and infants with normal hearing (NH) show a preference for listening to IDS over ADS. This preference may be adaptive as IDS also facilitates early language learning. Infants with hearing impairment (HI), who received a degraded speech signal, may not have sufficient access to pitch contours present in IDS to benefit from it during early language learning. Thus, the purpose of this study is to 1) determine whether infants with HI also prefer IDS over ADS, and 2) to compare the acoustic characteristics of speech directed to NH and HI infants in their home environment. Thirty-six infants, 9 HI infants, 9 NH hearing-matched controls and 9 NH chronological age-matched controls were tested on their listening preference for IDS over ADS using a central fixation preference procedure. Three to six hours of spontaneous infant-parent conversational interactions were audio recorded in the home with a digital recorder (LENA), for each infant. Five-minute segments were randomly selected and acoustically analyzed. Results confirmed that HI infants significantly preferred listening to IDS over ADS. The preference for IDS was also seen in younger hearing-matched NH controls, but not older NH controls. Preliminary production data from the mothers of 5 HI and 5 NH infants suggests that mothers of HI infants produce their utterances with a higher maximum pitch. Our results suggest that HI infants appear to have sufficient access to the speech signal to display a developmentally appropriate preference for IDS over ADS. Exaggerated pitch contours seen in parents' speech to their HI infants may support preferences for IDS at this critical time in language development.