Research indicates that infants lose the capacity to perceive distinctions in nonnative sounds as they become sensitive to the speech sounds of their native language (i.e., by 10- to 12-months of age). However, investigations into the decline in nonnative phonetic perception have neglected to examine the role of non-linguistic information. Exaggerated prosodic intonation and facial input are prominent in the infants' language-learning environment, and both have been shown to ease the task of speech perception. The current investigation was designed to examine the impact of infant-directed (ID) speech and facial input on infants' ability to discriminate phonemes that do not contrast in their native language. Specifically, 11-month-old infants were tested for discrimination of both a native phoneme contrast and a nonnative phoneme contrast across four conditions, including an auditory manipulation (ID speech vs. AD speech) and a visual manipulation (Face vs. Geometric Form). The results indicated that infants could discriminate the native phonemes across any of the four conditions. Furthermore, the infants could discriminate the nonnative phonemes if they had enhanced auditory and visual information available to them (i.e., if they were presented in ID speech with a synchronous facial display), and if the nonnative discrimination task was the infants' first test session. These results suggest that infants do not lose the capacity to discriminate nonnative phonemes by the end of the first postnatal year, but that they rely on certain language-relevant and non-linguistic sources of information to discriminate nonnative sounds. / Ph. D.

This research expands our understanding of the relationship between orthographic knowledge and phoneme perception by investigating how orthographic knowledge affects phoneme perception not only in the first language (L1) but also in the second language (L2), and an unfamiliar language (L0). Specifically, this research sought not only to confirm that L1 orthographic knowledge influences L1 phoneme perception, but also to determine if L1 orthographic knowledge influences L2 and L0 phoneme perception, particularly as it relates to native English speakers. Via a phoneme counting task, 52 participants were divided into two experimental groups—one with a Russian L0 and one with a Mandarin L0—and counted phonemes in words from their L1 (English) and L0. In addition, two subgroups of participants also counted phonemes in their L2 (either Russian or Mandarin). The stimuli for each language were organized along two parameters: 1) match (half with consistent letter-phoneme correspondences and half with inconsistent correspondences) and 2) homophony (half with cross-language homophonous counterparts and half without homophonous counterparts). The assumption here was that accuracy and RT differences would indicate an effect of orthographic knowledge on phoneme perception. Four-way repeated measures ANOVAs analysed the data along four independent factors: group, language, homophone, and match. Overall, the results support the hypotheses and indicate that L1 orthographic knowledge facilitates L1 and L0 phoneme perception when the words have consistent letter-phoneme correspondences but hinders L1 and L0 phoneme perception when the words have inconsistent correspondences. Similarly, the results indicate that L2 orthographic knowledge facilitates L2 phoneme perception with consistent words but hinders L2 phoneme perception with inconsistent words. On a more specific level, results indicate that not all letter-phoneme mismatches are equal in terms of their effect on phoneme perception, for example mismatches in which one letter represents two sounds (e.g., <x> = /ks/) influence perception more so than do mismatches in which one or more letters are silent (e.g. <sh> = /ʃ/). Findings from this research support previous claims that orthographic and phonological information are co-activated in speech processing even in the absence of visual stimuli (e.g., Blau et al., 2008; Taft et al., 2008; Ziegler & Ferrand 1998), and that listeners are sensitive to orthographic information such that it may trigger unwanted interference when the orthographic and phonological systems provide conflicting information (e.g., Burnham, 2003; Treiman & Cassar, 1997). More importantly, findings show that orthographic effects are not limited to L1. First, phoneme perception in unfamiliar languages (L0) is also influenced by L1 orthography. Second, phoneme perception in L2 is influenced by L2 orthgraphic interference. In fact, L2 orthographic effects appear to override any potential L1 orthographic effects, suggesting orthographic effects are language-specific. Finally, the preliminary findings on the different types of letter-phoneme mismatches show that future research must tease apart the behaviours of different kinds of letter-phoneme inconsistencies. Based on the findings, this dissertation proposes the Bipartite Model of Orthographic Knowledge and Transfer. The model identifies two components within L1 orthographic knowledge: abstract and operational. The model predicts that abstract L1 orthographic knowledge (i.e., the general assumptions and principles about the function of orthography and its relationship to phonology) transfers into nonnative language processing regardless of whether the listeners/speakers are familiar with the nonnatiave language (e.g., Bassetti, 2006; Vokic, 2011). In contrast, the model predicts that operational knowledge (i.e., what letters map to what phonemes) transfers into the nonnative language processing in the absence of nonnative orthographic knowledge (i.e., the L0), but does not transfer in the presence of nonnative orthographic knowledge (i.e., the L2). Rather, L2-specific operational knowledge is created based partly on the transferred abstract knowledge. The research here contributes to the body of literature in four ways. First, the current research supports previous findings and claims regarding orthographic knowledge and native language speech processing. Second, the L2 findings provide insight into the relatively sparse—but growing—understanding of the relationship between L1 and L2 orthography and nonnative speech perception. Third, this research offers a unified (albeit preliminary) account of orthographic knowledge and previous findings by way of the Bipartite Model of Orthographic Knowledge and Transfer. / Graduate

Previous research indicates that humans develop a phonological library in infancy. As humans grow into adulthood, their phonological library becomes well established. Upon encountering phonemes from a new language, humans process these phonemes by comparison to their native phonological library. Event-related potentials (ERP), specifically the mismatch negativity, have been shown to indicate that this process of comparing non-native phonemes to our native phonological library is not improved through learning the new language as an adult. An alternative explanation may be that there is an underlying change in the neural generators as the non-native phonemes are learned, but that this change is not reflected in the ERP. The current study seeks to examine this hypothesis through the simultaneous collection of ERP and blood-oxygen-level-dependent functional MRI (fMRI) data. The findings of the ERP and fMRI data are inconclusive. The study also explores the processing of diphthongs, a category of phonemes rarely tested before, through both behavioral and neuroimaging methods. The study presents behavioral data demonstrating that non-native diphthongs are processed based upon the separate elements of the phonemes, rather than as complete units.

Abstract This work was aimed at studying speech perception and auditory performance in the everyday lives of Finnish-speaking postlingually severely or profoundly hearing-impaired adults before and after receiving a multichannel cochlear implant. The association between the formal speech perception results and auditory performance in everyday life was also determined, and an effort was made to define how well a smaller sample represents the nationwide results. The patient series comprised a nationwide retrospective survey (N = 67), in which data on hearing level and word recognition were requested from the hospitals, and a prospective sample from the city of Oulu (N = 20), in whom hearing level, sentence, word and phoneme recognition and phoneme confusions were examined using standardised audiometric measures and formal speech perception tests in a study with a prospective repeated measure design. Categories of auditory performance in everyday life were assessed in both samples. The median sound field hearing level at frequencies of 0.5, 1, 2 and 4 kHz for the subjects in the nationwide survey one year after the switch-on of the implant was comparable to the level of mild hearing impairment. All the subjects achieved at least some open-set word recognition auditorily only (mean 71%, 95% CI 61-81%). The results in the Oulu sample were in line with the nationwide survey. A majority of the subjects (31/40) was able to understand conversation without speechreading one year after switch-on. Sentence recognition by the subjects in the Oulu sample improved most during the initial six months after the switch-on of the implant, whereas word and phoneme recognition improved steadily during the two-year follow-up period. Estimated average sentence recognition after two years was 89% (95% CI 71 to 106%), word recognition 73% (95% CI 58 to 87%), syllable recognition 53% (95% CI 42 to 63%), vowel recognition 80% (95% CI 68 to 92%) and consonant recognition 67% (95% CI 57 to 76%). Confusion of phonemes took place more in the direction a spectral energy distribution at higher frequencies. The association between auditory performance in everyday life and the formal speech perception tests was high (rs > 0.81, p &lt; 0.0001). Systematic prospective assessment of speech perception with tests of differing difficulty is recommended for the follow-up of adult cochlear implant users. / Tiivistelmä Tämän työn tarkoituksena oli tutkia suomenkielisten, kielen oppimisen jälkeen vaikean tai erittäin vaikean kuulovian saaneiden aikuisten kuulon tasoa, puheen vastaanottoa ja kuulon toiminnallista tasoa monikanavaisen sisäkorvaistutteen avulla. Tutkimuksessa selvitettiin myös, miten puheen vastaanottoa mittaavat testit kuvaavat selviytymistä arkipäivän elämässä sisäkorvaistutteen mahdollistaman kuulon avulla. Tarkoituksena oli myös määrittää, millä tavalla pieni otos edustaa kansallisia tuloksia. Tutkimuksessa on retrospektiivinen kansallinen otos (N=67) ja prospektiivinen Oulun otos (N=20). Kansallisessa otoksessa tiedot kuulon tasosta ja sanojen tunnistuskyvystä kerättiin yliopistosairaaloista koehenkilöiden sairauskertomuksista. Oulun otoksessa kuulon tasoa, sekä lauseiden, sanojen ja äänteiden tunnistuskykyä ja äänteiden sekoittuvuuksia tutkittiin audiometrian ja puheenvastaanottoa mittaavien testien avulla kahden vuoden seurannan aikana. Kuulon toiminnallista tasoa arvioitiin kuulon toiminnallisen tason luokituksella molemmissa otoksissa. Kansallisen otoksen koehenkilöiden kuulokynnysten mediaani äänikentässä sisäkorvaistutteella taajuuksilla 0,5, 1, 2 ja 4 kHz oli verrattavissa lievän kuulovian tasoon vuosi sisäkorvaistutteen käyttöönoton jälkeen. Kaikki koehenkilöt kykenivät tunnistamaan vähintään joitain sanoja pelkästään kuulonvaraisesti (keskiarvo 71 %, 95 %:n luottamusväli 61-81 %). Oulun otoksen ja kansallisen otoksen tulokset olivat yhteneväiset. Vuosi sisäkorvaistutteen käyttöönoton jälkeen suurin osa (31/40) koehenkilöistä pystyi keskustelemaan ilman huulioluvun tukea hiljaisessa ympäristössä. Oulun otoksen koehenkilöiden lauseiden tunnistuskyky parani eniten ensimmäisten kuuden kuukauden aikana. Sanojen ja äänteiden tunnistuskyky parani koko kahden vuoden seurannan ajan. Kaksi vuotta sisäkorvaistutteen käyttöönoton jälkeen, estimoitu keskimääräinen lauseiden tunnistusprosentti oli 89 % (95 %:n luottamusväli 71-106 %), sanojen tunnistusprosentti oli 73 % (95 %:n luottamusväli 58-87 %), tavujen tunnistusprosentti oli 53 % (95 %:n luottamusväli 42-63 %), vokaalien tunnistusprosentti oli 80 % (95 %:n luottamusväli 68-92 %) ja konsonanttien tunnistusprosentti oli 67 % (95 %:n luottamusväli 57-76 %). Koehenkilöt sekoittivat vokaaleja ja konsonantteja useimmiten spektraaliselta energialtaan läheisimpään suuremmille taajuuksille sijoittuvaan äänteeseen. Kuulon toiminnallisen tason luokituksen ja puheen vastaanottoa mittaavien testien välinen korrelaatio oli korkea (rs > 0.81, p &lt; 0.0001). Sisäkorvaistutteen saavien aikuisten kuulon tason ja puheen vastaanottokyvyn systemaattinen seuranta vaikeudeltaan eritasoisten testien avulla on tärkeää monipuolisen kuntoutuksen suunnittelun tueksi.

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