Overcoming the Effects of Variation in Infant Speech Segmentation: Influences of Word Familiarity

Abstract

Previous studies have shown that 7.5-month-olds can track and encode words in fluent speech, but they fail to equate instances of a word that contrast in talker gender, vocal affect, and fundamental frequency. By 10.5 months, they succeed at generalizing across such variability, marking a clear transition period during which infants' word recognition skills become qualitatively more mature. Here we explore the role of word familiarity in this critical transition and, in particular, whether words that occur frequently in a child's listening environment (i.e., "Mommy" and "Daddy") are more easily recognized when they differ in surface characteristics than those that infants have not previously encountered (termed nonwords). Results demonstrate that words are segmented from continuous speech in a more linguistically mature fashion than nonwords at 7.5 months, but at 10.5 months, both words and nonwords are segmented in a relatively mature fashion. These findings suggest that early word recognition is facilitated in cases where infants have had significant exposure to items, but at later stages, infants are able to segment items regardless of their presumed familiarity.To master their native language, young learners must translate words they encounter into meaning. Although the mechanisms that permit word learning remain unclear, children begin to successfully learn words at a very early age, with word comprehension beginning as early as 10 months (Benedict, 1979) and a productive vocabulary shortly thereafter (Nelson, 1973). This process might appear uncomplicated, given how effortlessly infants appear to learn words, but there are quite weighty demands that they must meet before word learning can begin. Two of the most widely documented challenges a young learner confronts are the segmentation and variability problems. Segmentation refers to the fact that speech unravels as a continuous stream without convenient pauses inserted between words, making it incumbent on listeners to partition the signal appropriately (Jusczyk, 1997; van de Weijer, 1998). Variability refers to the fact that human speech contains acoustic information that does not signal linguistic distinctions. How our systems converge on constancy from inordinate variability remains a mystery in every domain of perception. In the domain of speech, learners must compose a finite phonetic and lexical inventory from a complex stream of input that varies substantially and, therefore, unpredictably.Infants' capacities to resolve the segmentation and variability problems have been investigated over the last 10 years. In a seminal study, Jusczyk and Aslin (1995) Correspondence should be addressed to Leher Singh, Department of Speech, Language & Hearing Sciences, Boston University, 635 Commonwealth Avenue, Boston, MA 02215. leher@bu.edu. NIH Public Access Author ManuscriptInfancy. Author manuscript; available in PMC 2010 November 16. (Barker & Newman, 2004;Houston & Jusczyk, 2000; Jusczyk & Hohne, 1997) have shown that infants retain memories of wo...

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