Kateřina Chládková

Context-specific acoustic differences between Peruvian and Iberian Spanish vowels

This paper examines four acoustic properties (duration F0, F1, and F2) of the monophthongal vowels of Iberian Spanish (IS) from Madrid and Peruvian Spanish (PS) from Lima in various consonantal contexts (/s/, /f/, /t/, /p/, and /k/) and in various phrasal contexts (in isolated words and sentence-internally). Acoustic measurements on 39 speakers, balanced by dialect and gender, can be generalized to the following differences between the two dialects. The vowel /a/ has a lower first formant in PS than in IS by 6.3%. The vowels /e/ and /o/ have more peripheral second-formant (F2) values in PS than in IS by about 4%. The consonant /s/ causes more centralization of the F2 of neighboring vowels in IS than in PS. No dialectal differences are found for the effect of phrasal context. Next to the between-dialect differences in the vowels, the present study finds that /s/ has a higher spectral center of gravity in PS than in IS by about 10%, that PS speakers speak slower than IS speakers by about 9%, and that Spanish-speaking women speak slower than Spanish-speaking men by about 5% (irrespective of dialect).

Czech spoken in Bohemia and Moravia

As a western Slavic language of the Indo-European family, Czech is closest to Slovak and Polish. It is spoken as a native language by nearly 10 million people in the Czech Republic (Czech Statistical Office n.d.). About two million people living abroad, mostly in the USA, Canada, Austria, Germany, Slovakia, and the UK, claim Czech heritage (Ministry of Foreign Affairs of the Czech Republic 2009). However, it is not known how many of them are native speakers of Czech. Sociolinguistically, the language situation in the Czech Republic bears diglossic features. There is a substantial gap between formal, highly codified language and the language used in everyday situations. Our aim is to describe the way most people speak most of the time rather than artificial orthoepic norms (for the latter see Palkova⁄ 1997: 320-345). Geographically, in the western part of the country (Bohemia and western Moravia) pronunciation is relatively homogeneous compared to the greater dialectal diversity of the east (the rest of Moravia), where several dialectal areas can be distinguished (Cvrˇcek 2010: 24). Still, there are a number of features common to Moravian dialects, distinguishing them clearly from the pronunciation of Bohemia and allowing native speakers to identify someone as either Bohemian or Moravian. The present paper elaborates on the earlier illustration of Czech (Dankovicˇova⁄ 1997a) by describing the differences between Bohemian Czech (BC), spoken by more than six million Czech citizens, and Moravian Czech (MC), spoken by about three-and-a-half million Czech citizens. At the same time, our illustration provides additional information about what both varieties have in common.

Pre-attentive sensitivity to vowel duration reveals native phonology and predicts learning of second-language sounds

In some languages (e.g. Czech), changes in vowel duration affect word meaning, while in others (e.g. Spanish) they do not. Yet for other languages (e.g. Dutch), the linguistic role of vowel duration remains unclear. To reveal whether Dutch represents vowel length in its phonology, we compared auditory pre-attentive duration processing in native and non-native vowels across Dutch, Czech, and Spanish. Dutch duration sensitivity patterned with Czech but was larger than Spanish in the native vowel, while it was smaller than Czech and Spanish in the non-native vowel. An interpretation of these findings suggests that in Dutch, duration is used phonemically but it might be relevant for the identity of certain native vowels only. Furthermore, the finding that Spanish listeners are more sensitive to duration in non-native than in native vowels indicates that a lack of duration differences in ones native language could be beneficial for second-language learning.

Comparing vowel perception and production in Spanish and Portuguese: European versus Latin American dialects

Recent acoustic descriptions have shown that Spanish and Portuguese vowels are produced differently in Europe and Latin America. The present study investigates whether comparable between-variety differences exist in vowel perception. Spanish, Peruvian, Portuguese, and Brazilian listeners were tested in a vowel identification task with stimuli sampled from the whole vowel space. The mean perceived first (F1) and second formant (F2) of every vowel category were compared across varieties. For both languages, perception exhibited the same between-variety differences as production for F1 but not F2, which suggests correspondence between produced F1 and perceived vowel height but not between F2 and frontness.

Detecting categorical perception in continuous discrimination data

We present a method for assessing categorical perception from continuous discrimination data. Until recently, categorical perception of speech has exclusively been measured by discrimination and identification experiments with a small number of repeatedly presented stimuli. Experiments by Rogers and Davis [1] have shown that using non-repeating stimuli along a densely-sampled phonetic continuum yields a more reliable measure of categorization. However, no analysis method has been proposed that would preserve the continuous nature of the obtained discrimination data. In the present study, we describe a method of analysis that can be applied to continuous discrimination data without having to discretize the raw data at any time during the analysis.

Perceptual adaptation of vowels generalizes across the phonology and does not require local context.

Listeners usually understand without difficulty even speech that sounds atypical. When they encounter noncanonical realizations of speech sounds, listeners can make short-term adjustments of their long-term representations of those sounds. Previous research, focusing mostly on adaptation in consonants, has suggested that for perceptual adaptation to take place some local cues (lexical, phonotactic, or visual) have to guide listeners’ interpretation of the atypical sounds. In the present experiment we investigated perceptual adaptation in vowels. Our first aim was to show whether perceptual adaptation generalizes to unexposed but phonologically related vowels. To this end, we exposed Greek listeners to words or nonwords containing manipulated /i/ or /e/, and tested whether they adapted their perception of the /i/-/e/ contrast, as well as the unexposed /u/-/o/ contrast, which represents the same phonological height distinction. Our second aim was to test whether perceptual adaptation in vowels requires local context. Thus, a half of our listeners heard the manipulated vowels in real Greek words, while the other half heard them in nonwords providing no phonotactic cues on vowel identity. The results showed similar adjustment of /i/-/e/ categorization and of /u/-/o/ categorization, which indicates generalization of perceptual adaptation across phonologically related vowels. Furthermore, adaptation occurred irrespective of whether local context cues were present or not, suggesting that, at least in vowels, adaptation can be based on the distribution of auditory properties in the input. Our findings, confirming that fast perceptual adaptation in adult listeners occurs even for vowels, highlight the role of phonological abstraction in speech perception.

F2 slope as a Perceptual Cue for the Front–Back Contrast in Standard Southern British English

Acoustic studies of several languages indicate that second-formant (F2) slopes in high vowels have opposing directions (independent of consonantal context): front [iː]-like vowels are produced with a rising F2 slope, whereas back [uː]-like vowels are produced with a falling F2 slope. The present study first reports acoustic measurements that confirm this pattern for the English variety of Standard Southern British English (SSBE), where /uː/ has shifted from the back to the front area of the vowel space and is now realized with higher midpoint F2 values than several decades ago. Subsequently, we test whether the direction of F2 slope also serves as a reliable cue to the /iː/-/uː/ contrast in perception. The findings show that F2 slope direction is used as a cue (additional to midpoint formant values) to distinguish /iː/ from /uː/ by both young and older Standard Southern British English listeners: an otherwise ambiguous token is identified as /iː/ if it has a rising F2 slope and as /uː/ if it has a falling F2 slope. Furthermore, our results indicate that listeners generalize their reliance on F2 slope to other contrasts, namely /ɛ/-/ɒ/ and /æ/-/ɒ/, even though F2 slope is not employed to differentiate these vowels in production. This suggests that in Standard Southern British English, a rising F2 seems to be perceptually associated with an abstract feature such as [+front], whereas a falling F2 with an abstract feature such as [-front].

Speaker and accent variation are handled differently: Evidence in native and non-native listeners

Listeners are able to cope with between-speaker variability in speech that stems from anatomical sources (i.e. individual and sex differences in vocal tract size) and sociolinguistic sources (i.e. accents). We hypothesized that listeners adapt to these two types of variation differently because prior work indicates that adapting to speaker/sex variability may occur pre-lexically while adapting to accent variability may require learning from attention to explicit cues (i.e. feedback). In Experiment 1, we tested our hypothesis by training native Dutch listeners and Australian-English (AusE) listeners without any experience with Dutch or Flemish to discriminate between the Dutch vowels /I/ and /ε/ from a single speaker. We then tested their ability to classify /I/ and /ε/ vowels of a novel Dutch speaker (i.e. speaker or sex change only), or vowels of a novel Flemish speaker (i.e. speaker or sex change plus accent change). We found that both Dutch and AusE listeners could successfully categorize vowels if the change involved a speaker/sex change, but not if the change involved an accent change. When AusE listeners were given feedback on their categorization responses to the novel speaker in Experiment 2, they were able to successfully categorize vowels involving an accent change. These results suggest that adapting to accents may be a two-step process, whereby the first step involves adapting to speaker differences at a pre-lexical level, and the second step involves adapting to accent differences at a contextual level, where listeners have access to word meaning or are given feedback that allows them to appropriately adjust their perceptual category boundaries.

Indexical and linguistic processing by 12-month-olds: discrimination of speaker, accent and vowel differences

Infants preferentially discriminate between speech tokens that cross native category boundaries prior to acquiring a large receptive vocabulary, implying a major role for unsupervised distributional learning strategies in phoneme acquisition in the first year of life. Multiple sources of between-speaker variability contribute to children’s language input and thus complicate the problem of distributional learning. Adults resolve this type of indexical variability by adjusting their speech processing for individual speakers. For infants to handle indexical variation in the same way, they must be sensitive to both linguistic and indexical cues. To assess infants’ sensitivity to and relative weighting of indexical and linguistic cues, we familiarized 12-month-old infants to tokens of a vowel produced by one speaker, and tested their listening preference to trials containing a vowel category change produced by the same speaker (linguistic information), and the same vowel category produced by another speaker of the same or a different accent (indexical information). Infants noticed linguistic and indexical differences, suggesting that both are salient in infant speech processing. Future research should explore how infants weight these cues in a distributional learning context that contains both phonetic and indexical variation.

When "AA" is long but "A" is not short : speakers who distinguish short and long vowels in production do not necessarily encode a short-long contrast in their phonological lexicon

In some languages (such as Dutch), speakers produce duration differences between vowels, but it is unclear whether they also encode short versus long speech sounds into different phonological categories. To examine whether they have abstract representations for ‘short’ versus ‘long’ contrasts, we assessed Dutch listeners’ perceptual sensitivity to duration in two vowel qualities: [a] and [ɑ], as in the words maan ‘moon’ and man ‘man,’ which are realized with long and short duration respectively. If Dutch represents this phonetic durational difference as a ‘short’–‘long’ contrast in its phonology, duration changes in [a] and [ɑ] should elicit similar neural responses [specifically, the mismatch negativity (MMN)]. However, we found that duration changes evoked larger MMN amplitude for [a] than for [ɑ]. This finding indicates that duration is phonemically relevant for the maan-vowel that is represented as ‘long,’ while it is not phonemically specified for the man-vowel. We argue that speakers who in speech production distinguish a given vowel pair on the basis of duration may not necessarily encode this durational distinction as a binary ‘short’–‘long’ contrast in their phonological lexicon.