Stress patterns and vowel quality in Dutch infant-directed speech

Abstract

It has been well documented that infant-directed speech (IDS) differs in prosody from adult- directed speech (ADS) and is thought to facilitate language acquisition. This study focuses on word stress, because it is important for lexical representation and might therefore play a big role in language acquisition. This study aims to investigate the prosodic properties of stress in Dutch IDS compared to Dutch ADS to see if there are differences in the indicators of stress. Additionally, this study aims to investigate if there are differences in stress and vowel quality in IDS for gender of the addressee. The participants consisted of 22 mother-infant pairs, of which 11 were mother-son pairs, and 11 were mother-daughter pairs. The data were collected from video and audio recordings of picture book readings to both the infant and the experimenter. Results showed that the difference in mean pitch between unstressed and stressed syllables and vowels was higher in IDS than in ADS. Furthermore, pitch minimum and pitch maximum were both higher in vowels of stressed syllables in IDS than in vowels of stressed syllables in ADS. A trend was found that the different types of pitch measures (mean pitch, minimum pitch, maximum pitch and pitch range) are higher in stressed syllables (and vowels) in IDS than in stressed syllables (and vowels) in ADS. For IDS directed to girls a trend was found that the same pitch measures were higher in stressed syllables than in IDS directed to boys. Thus, IDS directed to girls seemed to show an exaggerated pattern of the one that was found for IDS in general. Further research with additional participants should indicate if the found trends are representative for stress in Dutch IDS. Furthermore, additional research should indicate what the role of duration and vowel quality might be as stress markers.