The acquisition of speech sound categories on the basis of distributional information

In order to account for speech sound patterns in language, linguists posit the existence of abstract sound categories called phonemes. In this dissertation I discuss three important aspects of the phoneme---the contrastive, featural, and allophonic aspects---and develop hypotheses for how a language learner might acquire each aspect. I present experimental evidence regarding the acquisition of phonemic contrasts, and preliminary findings regarding the acquisition of phonological features.;A review of the evidence for the psychological reality of each aspect of the phoneme demonstrates that phonemic contrasts and phonological features are instantiated in the mind of language speakers. Phonemic contrasts affect speech perception, and phonological features play a role in production, perception, and short term memory. The psychological reality of allophones, however, has not been conclusively documented.;Infants acquire the phonemic contrasts of their native language during their first year. To account for this, I argue for a distribution-based model, in which phonemic contrasts are learned on the basis of how frequently a learner hears particular sounds in a given phonetic context. I support this model through two experiments in which adult subjects are presented with a language they have never heard before and are tested on their acquisition of the language's contrasts. The only information available to the subjects for determining the language's system of contrasts comes from the frequency distribution with which the sounds are presented during the training phase of the experiment. The results demonstrate that subjects are able to make use of distributional information for learning phonemic contrasts.;The second experiment also tests whether subjects extract the phonological features of the contrasts in question. The results indicate that the subjects did not learn phonological features, but these results are argued to result from limitations in the stimuli.;The goal of this dissertation is to delineate what is already known about the psychological reality of the three aspects of the phoneme, in order to account for their acquisition. The experiments conducted support a distribution-based model of phonemic contrast acquisition, and hypotheses are proposed regarding the acquisition of phonological features and allophones.