Perception of similar sounds as a function of language dominance
in late bilinguals of English and Spanish

A critical stage in second language (L2) development is the discrimination between first language (L1) and L2 similar sounds, that is, sounds with a smaller perceived phonetic distance (Flege, 1987, 1995), as this may have significant consequences for ultimate native-like attainment in the L2 for both perception and production skills (Escudero, 2007; Flege, 1993). Previous studies (Kissling, 2015; Vokic, 2010) suggest that course level and language experience fail to adequately reflect perceptual accuracy. Furthermore, even within groups of speakers matched for age of arrival (AoA) and length of residence (LOR), there is significant variation in L2 perceptual abilities (Aoyama & Flege, 2011). This study examines the L2 perception of Spanish approximants [β, δ, ɣ] in comparison with their voiced stop counterparts [b, d, g] by English-Spanish bilinguals. Specifically, it considers the effect of multiple learner variables including proficiency, language history, attitudes and L1/L2 use, as these variables comprise bilingual language dominance. This study therefore investigates how language dominance, as measured by the Bilingual Language Profile questionnaire (Birdsong et. al., 2012), variably influences late bilinguals’ ability to discriminate similar sounds in Spanish. Perception of target phones was assessed in adult English-Spanish bilinguals (n = 33) of varying proficiency levels via VCV nonwords featuring both Spanish approximates [β, δ, ɣ] and voiced stops [b, d, g] in intervocalic position in an AX discrimination task. Both Spanish learners (n=23) and native Spanish speakers (n=10) were tested and participants were then grouped by language dominance score: English-dominant, Spanish-dominant, and near-balanced bilinguals. Results indicate that the perceptual difficulty of similar L1/L2 phones is crucially a function of an individual’s primary/dominant language, as results suggest that language dominance modulates perception more than proficiency and course level. Findings further show that perceptual accuracy is varied and depends on the specific phonetic contrast. The present study effectively collapses the combined effect of language history, use, proficiency and attitudes into one concise score (language dominance) thereby contributing a more nuanced examination of L2 perception that goes beyond proficiency and experience alone, as previously studied (Bohn & Flege, 1990; Aoyama & Flege, 2011; Kissling, 2015). Findings indicate which similar phones present the most perceptual difficulty (namely, [ɣ] / [g] and [δ] / [d]) and therefore should be the focus of explicit phonetic instruction for adult Spanish learners in the university classroom context.