The Effect of Perceived Phonetic Similarity on Non-Native Sound Learning by Children and Adults

It is axiomatic that most children, unlike adults, learn to speak and understand a second language (L2) in a native-like manner1 (Munro, Flege, & MacKay, 1996). One of the most salient factors influencing the outcome of child and adult L2 learning is the effect of the leamer's native language (Ll) on the ability to learn L2 consonants and vowels (or "sounds" for short). Adult L2 learners' speech perception and production are often influenced by their native language. By contrast, as studies using a retrospective developmental design have indicated, individuals who began learning their L2 as children usually approximate the phonetic system of the LI more closely than individuals who began learning their L2 as adults (Flege, MacKay, & Meador, 1999; Mack & TrofrnlOvich, 2001; Mack, in press). However, few studies have directly comp~red adult and child L2 learners, as was done in the present study. According to Flege's Speech Learning Model (SLM), an important source of child-adult differences observed in L2 speech learning is the interaction between the L 1 and L2phonetic systems at the time of first exposure to an L2 (Flege, 1995; 1999). This tenet of the SLM rests on two claims. The first presupposes that accurate L2 perception and production, indicative of developing long-term representations (categories) for L2 sounds, are attainable if the L2 learner perceives the phonetic differences that exist between L 1 and L2 sounds or if L2 sounds are not strongly perceptually identified with L I sounds (Flege, 1995; Best & Strange, 1992). The second claim states that, as the sound categories making up the L 1 phonetic system slowly develop through childhood and into adolescence (Ohde, Haley, & McMahon, 1996; Sharma, Kraus,