There has been an increasing interest in the studies on L3 acquisition in phonology over the past two decades. In terms of L3 acquisition, it is commonly viewed as an extension of second language (L2) acquisition. In fact, the process of L3 acquisition is rather complex as it will be influenced by a learner’s first language (L1) and L2 instead of L1 alone as the major source of cross-linguistic influence (CLI) in SLA (Cenoz et al., 2001; Williams & Hammarberg, 1998). As for CLI, it refers to the influence of prior linguistic knowledge on the production, comprehension, and development of a target language. Therefore, to L3 learners who have already acquired their first foreign language (i.e., L2) may acquire L3 by relying on the conscious linguistic knowledge of their L1 and L2 as well as language-learning experience and strategies (De Angelis 2007).
The policy of “biliteracy and trilingualism”, which encourages Hong Kong citizens to be biliterate in written Chinese and English and trilingual in spoken Cantonese, English, and Mandarin, has been shaping the design and implementation of curricula in Hong Kong primary and secondary schools and has had an impact on language use in Hong Kong since the handover in 1997 (Wang & Kirkpatrick, 2013). Most Hong Kongers have been aware of the urgent need to train themselves to at least a basic functional level of proficiency in their second language (L2) and third language (L3), the level at which L2 and L3 is sufficient for general social and workplace communication. However, it is commonly observed in our daily life that if a Cantonese learner from Hong Kong takes English as L2, his/her pronunciation of three /θriː/ would be possibly pronounced as /friː/, whereas if a Cantonese learner from Guangdong province takes Mandarin as L2 and English as L3, three /θriː/would be possibly pronounced as /sriː/. It seems that one of the most prominent factors people may notice when an L2 or L3 speaker begins speaking is pronunciation. Almost instantly, nonnative pronunciation can be identified. Nonnative pronunciation may have some undesired consequences (Flege, 1995). Listeners may quickly tag the accented speech with labels, such as “slow,” “needing help,” and other descriptions associated with ineffective communicators.