Learning to hear new speech sounds: A dynamical approach

When adults attempt to learn new speech sounds, they do so in the context of the phonology of their native language. The purpose of the present work is to investigate the nature of the learning process; that is, to examine, in individuals, (1) the process of acquiring a new phonetic category, (2) the impact of learning a new phonetic category on a similar, existing category, and (3) transfer of learning to a novel phonetic context. Monolingual American English speakers were required to learn the Hindi voiced, unaspirated, dental stop consonant. Two synthetic speech continua (one voiced, the other voiceless) were created, spanning a range from Hindi dental to American English alveolar stop consonants. Subjects underwent a perceptual mapping procedure that included identification, judged goodness, and difference-rating tasks in order to establish how they perceived the stimuli initially. Then they participated in a two-alternative, forced-choice training program using only voiced, natural speech stimuli. Progress was monitored throughout training. Following training, the mapping procedure was repeated with both the voiced and voiceless continua. After at least a two-week delay with no further training, subjects participated in a follow-up test. Results indicate that the nature of change during the learning process depends on how the individual listener perceives the stimuli prior to training and on the order of presentation of stimuli.