The Effects of Age of Onset on VOT in L2 Aquisition and L1 Attrition : A Study of the Speech Production and Perception of Advanced Spanish-Swedish Bilinguals

Sammanfattning: This thesis explores the role of age in second language (L2) acquisition and first language (L1) attrition. The focus is on Voice Onset Time (VOT) in the production and categorical perception of word-initial L1 and L2 stops in highly advanced L1 Spanish learners of L2 Swedish. Using as the point of departure a maturational constraints perspective and the Critical Period Hypothesis (CPH), Study I examines the impact of age of onset (AO) of L2 acquisition on the production of L2 Swedish voiceless stops. The results show that there are AO effects even in the speech of highly advanced L2 learners and that the incidence of nativelike L2 learners is considerably lower than earlier assumed. However, conclusions like these are only possible when speaking rate is accounted for, thereby highlighting the importance of speaking rate effects on VOT as a measure of nativelikeness. Like Study I, Study II reveals age effects on the same L2 learners’ categorical perceptions of L2 Swedish stops. Moreover, after combining the results with the data from Study I, the incidence of nativelike behavior drops remarkably with no late L2 learner performing within the range of native-speaker production and perception. The results suggest that L2 acquisition of phonetic/phonological aspects is especially sensitive to AO effects. It is concluded that theories on maturational constraints, including the CPH, cannot be refuted on the basis of the present data. Study III concerns the same participants’ production and perception of L1 Spanish stops. Age of reduced contact (ARC) is identified as an important predictor for L1 attrition and retention of voiceless stop production, although not of stop perception. This discrepancy is related to different activation thresholds as proposed by the Activation Threshold Hypothesis (ATH). It is further suggested that early bilinguals are more dependent on high-frequency L1 use than late bilinguals when compensating for age effects, but only in production.