Doctoral Dissertation Research: The acquisition of phoneme categories

University Of North Carolina At Chapel Hill, Chapel Hill NC

Investigators

Abstract

Language comes effortlessly to children, and only adults learning a second language get a glimpse of the numerous intricacies involved in learning a language. These range from correlation of word to meaning, to something as deceptively simple as the categorization of speech sounds. To best illustrate this, we can look at two examples: differences in perception between English and Hindi speakers, and differences in perception between English and Japanese speakers. English speakers have trouble hearing the difference between the "p" in "pear" and the "p" in "spare," even though they are in reality pronounced quite differently. A speaker of Hindi on the other hand would have no trouble hearing this difference. To take another example, while English speakers could easily tell you that "light" and "right" begin with two different sounds, Japanese speakers find it very difficult to hear the difference between these two words. All of these difficulties arise as a byproduct of the human infant's very efficient learning mechanism when (s)he is first learning a language. The human brain unconsciously and automatically sorts the large amount of information we are constantly receiving into ordered data, even before we make conscious decisions. This study is concerned with determining what critical pieces of information were received by the Hindi infant to lead him or her to (unconsciously) determine that those were two different "p" sounds, while the English infant determined that they were the same sound; or what information led the Japanese infant to ignore the difference between "l" and "r" when acquiring Japanese, but did not lead the English infant to ignore the same difference. This study both contributes to broad theoretical issues within cognitive science by addressing how categories are learned by humans, and also leads to practical applications, such as more efficient second language learning techniques and advancements in speech pathology. Previous work has identified at least two main cues that humans use when categorizing sounds: the learner's growing vocabulary ("vocabulary cue") and acoustic properties found within a stream of speech ("acoustic cue"). The vocabulary cue groups together sounds occurring in similar word environments ("light" and "right") into a single sound category. The acoustic cue maps sounds into some acoustic map and picks out regions of high frequencies on this map. This study makes use of past observations that adults can unconsciously simulate, at least to some degree, aspects of the infant's learning experience within a laboratory setting. This experiment will test how much adults rely on each of these two cues by presenting participants with an artificial language where the vocabulary cue and the acoustic cue give the participant conflicting information. In this way, the research will contribute to a better understanding of what unconscious decisions the human brain makes when categorizing speech sounds. This study addresses two fundamental issues within linguistics and within cognitive science: (1) how the human brain forms complex categories, and (2) how much of language is acquired through specialized language-specific modules and how much of language can be attributed to general cognitive mechanisms.