Exploring Early Language Acquisition from Different Kinds of Input: The Role of Attention

Abstract

While most research on infant word segmentation has investigated the extraction of words from fluent speech in standard laboratory settings, the series of experiments in this dissertation examined the role of different kinds of input and exposure on infants’ word segmentation and word learning abilities. The first experiment suggests that infants are able to successfully segment words from fluent infant-directed speech (hereafter, IDS), which includes longer pauses, shorter utterances, higher fundamental frequencies, and wider pitch ranges, but also the fast and monotone input of adult-directed speech (hereafter, ADS) provided they were familiarized with these words over an extended-exposure period of six weeks at home. These 9-month-old infants, however, seem to be unable to segment words from fluent IDS during a standard laboratory-familiarization. Therefore, the second experiment examined whether German infants might require a more exaggerated IDS exposure similar to the one American English infants are addressed with. Here, 9-month-old, but not 7.5-month-old, infants successfully segmented the words presented in an exaggerated IDS register. Using neurophysiological measures, the third experiment further explored 7.5-month-old infants’ segmentation abilities and revealed that these infants were only able to successfully segment words from fluent exaggerated IDS. The final study of the dissertation extended the investigations to infants’ word learning abilities. Critically, infants were trained on word-object associations in fluent IDS or ADS. The results of this study demonstrated that infants were able to learn words regardless of the register they were trained in and suggest that infants are able to learn from a much greater variety of input available to them than previously suggested, extending the findings from word segmentation to word learning. Importantly, this dissertation presents the earliest evidence of ADS word segmentation and word learning presented in the literature to date. Hence, it provides new insights into infant word segmentation and word learning from different kinds of input and different kinds of exposure. Furthermore, the idea of attention as being a central mechanism in early language acquisition is supported by this dissertation.