Can native-language perceptual bias facilitate learning words in a new language?

Can native-language perceptual bias facilitate learning words in a new language? Bo˙zena Paj ak ˛ 1 (bpajak@ucsd.edu), Sarah C. Creel 2 (creel@cogsci.ucsd.edu), Roger Levy 1 (rlevy@ucsd.edu) 1 Department of Linguistics, 2 Department of Cognitive Science, UC San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA Abstract Acquiring a language relies on distinguishing the sounds and learning mappings between meaning and phonetic forms. Yet, as shown in previous research on child language acquisi- tion, the ability to discriminate between similar sounds does not guarantee success at learning words contrasted by those sounds. We investigated whether adults, in contrast to young infants, are able to attend to phonetic detail when learning sim- ilar words in a new language. We tested speakers of Korean and Mandarin to see whether they could use their native-language- specific perceptual biases in a word-learning task. Results re- vealed that participants were not able to fully capitalize on their perceptual abilities: only faster learners – as indepen- dently assessed by baseline trials – showed enhanced learning involving contrasts in phonetic dimensions informative in their native language. This suggests that attention to phonetic detail when learning words might only be possible for adults with better learning skills or higher motivation. Keywords: word learning; non-native speech perception; sec- ond language acquisition Introduction Humans are able to take advantage of many different re- sources available to them in the course of learning. For ex- ample, when learning a new language – whether in infancy or adulthood – humans actively search for regularities by an- alyzing the input in several alternative ways (e.g., examining either adjacent or non-adjacent dependencies; Gomez, 2002), and are able to simultaneously entertain multiple implicit the- ories about the input’s underlying structure (e.g., Gerken, 2010). One of the complex features of learning a language is that listeners must perform concurrent analyses of the input at different levels of processing and integrate these multiple pieces of information at once. If, for example, we zoom in to the level of processing single words, one needs to encode phonetic cues and, at the same time, map the phonetic form onto meaning. This task may be particularly hard for begin- ner second language (L2) learners who are not yet familiar with the L2 sound system, especially when they are process- ing words with novel sounds that do not exist in their native language (L1). However, there is evidence that learners capi- talize on whatever pieces of information are available to them to achieve this task: they might use lexical cues to make in- ferences about sound categorization (Feldman, Myers, White, Griffiths, & Morgan, 2011), and – conversely – take advan- tage of perceptual learning on sound categorization to help them make inferences about the lexicon (Perfors & Dunbar, 2010). The question we are addressing in this paper is another piece of this puzzle. Specifically, we know that prior language knowledge is one of the starting points when learning a new language: L1-based perceptual biases can facilitate perception of novel sound contrasts that differ along phonetic dimensions informative in L1 (Pajak, 2010a, 2010b; Pajak & Levy, in prep.), and can affect interpretation of distributional information from novel language input (Pajak & Levy, to appear). How efficiently, then, do adults capitalize on their L1-based phonetic general- izations when learning the lexicon in a new language? Intuitively, it might seem that whatever perceptual abili- ties adults have, they should be able to use them both when distinguishing sounds and when learning novel words. That is, if they hear a distinction between sounds b and p, they should be able to easily distinguish between words like ban and pan. However, the picture emerging from prior research is far less clear. In fact, research with young infants suggests that the ability to discriminate perceptually between similar sounds does not in general guarantee immediately success- ful learning of words that are contrasted by those sounds. At 14 months, infants can easily discriminate the sounds b and d. However, when taught that a novel object is called a bih, but later on is referred to as a dih, infants do not no- tice this mispronunciation (Stager & Werker, 1997). The ini- tial explanation proposed for this result was the limited re- source hypothesis (Stager & Werker, 1997; Werker, Fennell, Corcoran, & Stager, 2002): since attending to fine phonetic detail while learning new words is computationally very de- manding, young infants – who have limited attentional and cognitive resources – might have difficulty accessing all pho- netic detail when focusing their attention on learning mean- ing. Subsequent research showed that 14-month-old infants succeed only with additional contextual information or un- der less demanding learning conditions (Fennell & Werker, 2003; Fennell, Waxman, & Weisleder, 2007; Rost & McMur- ray, 2009; Swingley & Aslin, 2002; Thiessen, 2007; Yoshida, Fennell, Swingley, & Werker, 2009). Some evidence suggests that adults might have similar dif- ficulties when learning words in a new language. In a study by Perfors and Dunbar (2010), native speakers of English were first trained on discriminating a non-native contrast be- tween a prevoiced and a voiceless unaspirated stop ([gipur] vs. [kipur]), and then taught word-picture mappings using minimal-pair words distinguished by this non-native contrast. The results showed that while participants performed better than chance at learning similar words with the exact con- trast they had been trained on ([gipur]-[kipur]), they were at chance at learning words contrasted by sounds with an analo- gous contrast ([bipur]-[pipur]). This was despite the fact that, after perceptual training on [g]-[k], participants were able to distinguish [b] and [p] perceptually. Thus, just like 14-month- old infants, adults had difficulty differentiating between simi- lar words in a word-learning task, even though they could tell these words apart in a pure perceptual task. 1 1 Better performance on [gipur] and [kipur]) might have been due