Ab initio word recognition in infant- and adult-directed continuous speech

Continuous speech presents a challenge to the ab initio learner, as the language-specific segmentation strategies they use in their first language are not always reliable cues in other languages (Cutler 2001 International Journal of Research and Practice in Interpreting, 5(1), 1-23). Yet, they are able to use more general acoustic, prosodic, and statistical cues to word boundaries, as well as lexical similarity to their first language (e.g., Shoemaker & Rast 2013. Second Language Research, 29(2), 165-183) to recognize words at first exposure to a new language. In the current study, we investigated whether adult ab initio learners' ability to recognize words after brief exposure to continuous speech in a new language is improved when that speech is produced using an infant-directed register, a style of speech found to facilitate segmentation in infancy (Thiessen et al. 2005. Infancy 7(1), 53-71). In a series of experiments, we demonstrate that although English ab initio learners of German benefited from infant-directed speech, their performance was generally lower than in previous studies unless task demands were reduced. These learners also benefited from word length and from frequency of occurrence, as has been shown previously, but these did not interact with register. As in infancy, learner-directed speech registers appear to facilitate initial processing and recognition in adult ab initio learners.