The relationship between speech perception and word learning at the initial state of second language acquisition

The goal of most adult second language (L2) learners is to confidently and efficiently communicate in their target L2. However, this task is not easy. In order to produce new L2 words a learner first needs to perceive the sounds that comprise these words. Considered effortless in one’s native language (L1), distinguishing novel L2 phonemes can be quite difficult for adult learners, and difficulties in L2 speech perception are often attributed to the negative transfer effects of the L1. Research suggests that the size of the L2 vowel inventory relative to the L1 inventory may affect the discrimination and acquisition of L2 vowels. Specifically, if the L1 has a smaller L1 vowel inventory than the L2 this may obstruct L2 vowel perception, while if the L1 has a larger vowel inventory it often facilitates vowel perception. However, the Second Language Linguistic Perception (L2LP) model specifies that it is the L1-L2 acoustic relationships that predict L2 vowel perception, regardless of L1 vowel inventory size. The model further posits that there is continuity between L2 perception and L2 word learning (Escudero, 2005, 2006, 2009; van Leussen & Escudero, 2015). In this view, sounds that are difficult to perceive would yield comparable difficulty in learning L2 words containing the same sounds. The present thesis investigates Australian English (AusE), Peruvian Spanish (PS) and Spanish adult listeners’ non-native vowel perception and word learning of Dutch and the interrelation between these two abilities. In order to establish the initial state of learning the present thesis examines naïve listeners (i.e., AusE, PS and Spanish monolinguals) with no prior knowledge of Dutch. This thesis comprises two studies, as well as an Introduction and General Discussion. Study 1 investigates the effects of vowel inventory size versus acoustic properties on non-native vowel perception. It compares XAB discrimination and categorization of five Dutch vowel contrasts between monolinguals whose L1 contains more (AusE) or fewer (PS) vowels than Dutch. It also examines whether cross-language discriminant analyses predict listeners’ categorization patterns and whether these in turn predict their discrimination ability. Study 2 investigates the interrelation between listeners’ initial perceptual and word learning abilities by comparing two sets of previously published data. AusE and PS listeners’ XAB discrimination of five Dutch vowel contrasts, which was presented in Study 1, is compared to AusE and Spanish non-native word learning of minimal pairs containing the same vowel contrasts, which was previously reported in Escudero (2015). This comparison between perception and word learning data sets is done quantitatively, using the same statistical models, and also qualitatively. Results show that the size of participants’ native vowel inventories did not affect performance in either task. Rather it is the L1-L2 acoustic relationships that predicted listeners’ non-native categorisation and discrimination patterns and these in turn predicted their word learning difficulties. Specifically, minimal pair words containing perceptually difficult vowel contrasts were more difficult to discriminate, while word pairs containing perceptually easy contrasts were easier. Results presented in both studies confirm the L2LP proposal that there is continuity between perception and recognition in L2 development

Auditory perceptual learning in autistic adults

The automatic retuning of phoneme categories to better adapt to the speech of a novel talker has been extensively documented across various (neurotypical) populations, including both adults and children. However, no studies have examined auditory perceptual learning effects in populations atypical in perceptual, social, and language processing for communication, such as populations with autism. Employing a classic lexically-guided perceptual learning paradigm, the present study investigated perceptual learning effects in Australian English autistic and non-autistic adults. The findings revealed that automatic attunement to existing phoneme categories was not activated in the autistic group in the same manner as for non-autistic control subjects. Specifically, autistic adults were able to both successfully discern lexical items and to categorize speech sounds; however, they did not show effects of perceptual retuning to talkers. These findings may have implications for the application of current sensory theories (e.g., Bayesian decision theory) to speech and language processing by autistic individuals. Lay Summary: Lexically guided perceptual learning assists in the disambiguation of speech from a novel talker. The present study established that while Australian English autistic adult listeners were able to successfully discern lexical items and categorize speech sounds in their native language, perceptual flexibility in updating speaker-specific phonemic knowledge when exposed to a novel talker was not available. Implications for speech and language processing by autistic individuals as well as current sensory theories are discussed

More vowels are not always better : Australian English and Peruvian Spanish learners' comparable perception of Dutch vowels

Second-language (L2) learners frequently struggle with the perception of L2 sounds not present in their native language (Escudero; 2005, Escudero & Boersma, 2004; Fliege et al., 1997; Fox et al., 1995; Morrison, 2009). Vowels are especially difficult to master, presumably due to the continuous dimensions by which vowels can differ across languages (eg. Beddor & Strange, 1982; Polka & Bohn, 1996)

Acoustic distance explains speaker versus accent normalization in infancy

Acoustic/phonetic differences exist in cross-speaker and crossaccent speech. Young infants generally recognize speech across speakers but not across speakers of different accents. We examined how Australian English infants discriminated Dutch vowels produced by two speakers of the same accent, and by two speakers of two different accents. Acoustic analysis showed that the acoustic distance between samevowel tokens produced by speakers of different accents was larger than between those produced by speakers of the same accent. Infants demonstrated greater difference in looking time to an accent than a speaker change, indicating that they noticed a difference in a vowel produced in a different accent more than one produced by another speaker with the same accent. This supports the hypothesis that acoustic distance underlies the relative ease in handling speaker versus accent variation

Difficulty in discriminating non-native vowels : are Dutch vowels easier for Australian English than Spanish listeners?

Previous studies have shown that the number of vowels present in one’s L1 inventory may affect the ability to learn and discriminate non-native vowel contrasts. Specifically, learners whose L1 contains fewer vowels compared to the target language may find many non-native vowel contrasts novel and have discrimination performance lower than learners whose L1 contains more vowels than the target language for whom most of the non-native vowel contrasts will be familiar. The present study tested monolingual Australian English (AusE) listeners’ discrimination of non-native vowels in Dutch, which has fewer vowels compared to AusE. We further compared AusE listeners’ performance to that of native monolingual Spanish listeners whose L1 contains fewer vowels than Dutch. AusE listeners were able to discriminate all Dutch vowel contrasts above chance. While there was no main effect of language background, an interaction language background x contrast revealed that AusE listeners more accurately discriminated the /I-Y/ contrast compared to Spanish listeners, suggesting some advantage for AusE listeners. The findings are discussed in relation to models of non-native and L2 speech perception together with a comparison of vowel acoustic properties across AusE, Spanish and Dutch

Is more always better? : the perception of Dutch vowels by English versus Spanish listeners

The present study investigates Australian English (AusE) monolingual listeners’ perception of non-native vowels in Dutch, a language with fewer vowels compared to AusE. AusE listeners’ performance was compared to native monolingual Peruvian Spanish (PS) listeners whose L1 contains fewer vowels than Dutch. Results show that compared to PS listeners, AusE listeners were better at discriminating only one contrast, /ɪ -ʏ /. AusE listeners took full advantage of their vowel inventory size by mapping Dutch vowels across multiple English categories. Surprisingly, they also appear to duplicate the PS single category assimilation by mapping Dutch /ɪ / and /i/ to both English /i/ and /ɪ /