The perception of English stop consonants by Thai children and adults

This dissertation investigates the perception of stops by learners whose L1 has more stop categories than the L2. While these learners are not expected to have any difficulty learning these stop categories because of a wider inventory in their L1, additional data will provide a better understanding of how a second language is acquired. This study presents that learners do reorganize their phonological inventory when they learn a second language, even when there is no need to do so. In Experiment 1, Thai children and adults' perception of English stops was assessed using categorical discrimination and forced-choice identification experiments. While the Thai children identified English stops with the three categories of voicing contrast as found in Thai, the Thai adults responded with only two categories, as did the English speakers. The performance of the Thai children supports the Perceptual Assimilation Model, which posits that inexperienced learners do perceive non-native sounds according to the inventory of their L1. The performance of Thai adults, however, shows that they do not assimilate English and Thai stops that are phonetically similar, as predicted by the Speech Learning Model. Rather, they perceive English stops similarly to how native speakers perceive them. This finding suggests that the Thai adults somehow know that there are only two categories of stops in English.;A series of conditions were examined in Experiment 2 to investigate whether the Thai adults would be able to alter their responses depending on the language of the presentation, and allows us to better understand how the language of the stimuli affects the Thai adults in their judgments of stops. Results indicate that Thai speakers do not simply map English stops to Thai stops that are phonetically similar. Rather, they are aware of the language set of the stimuli, and are able to alter their responses according to the language they are listening to.