the blurring effect of sonorants and vocalic alternations in gaelic roy becker university college...

The Blurring Effect of Sonorants andVocalic Alternations in Gaelic

Roy Becker

University College Dublin

2003

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Main hypothesis:Vowel quality is perceptually blurred by the

presence of a following sonorant

Why ???• Co-articulatory effects

unique to sonorants alter the resonations, and hence the auditory image, of the vowel (this is well-known)

• Sonorants have backward masking effects on preceding vowels (really?)

So what ???• If accurate perception

(faithfulness) is important in language, then in case of substantial blurring, a faithfulness-oriented grammar should provide repair mechanisms against such blurring.

• Claim: this happened inEarly Modern Gaelic.

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The blurring effect of sonorants (1) Vowel perception – cues for vowel quality

(a) Auditory representation of the acoustic resonation patterns (formants) of the vowel kernel, eventually a function of the size and shape of the cavities of the vocal tract (e.g. Johnson 1997:64).

(what if the cavities are altered …?)

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The blurring effect of sonorants (1) Vowel perception – cues for vowel quality

(b) Vowel-specific co-articulatory effects over adjacent consonants, i.e. the acoustics of the consonant and/or the transition serve as a cue for the quality of the vowel, e.g. Liberman et al. (1967).Notice the spectrographic differences between the corresponding [z]’s and [l]’s] in the following spectrograms.

(what if such effects are absent, e.g. in the case of secondary articulation …?)

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The blurring effect of sonorants (2) Regressive co-articulatory colouring effects of sonorants

(a) Nasals: vowel nasalisation - anticipatory lowering of the velum (‘regressive nasalisation’) resulting in altered resonations due to coupling of the oral and nasal cavities (e.g. Wright 1986).

(b) Coronal Liquids: vowel ‘darkening’ - anticipatory retraction and lowering of the dorsum, a typical gesture that facilitates both tongue-tip vibration (trill), retroflection (approximant) and lateral aperture during central constriction (lateral). This anticipatory gesture is particularly common for coda liquids, and results in altered resonations of the oral cavity (e.g. Sproat & Fujimura 1993).

(c) Dorsal Rhotics: transitional quality - trills and approximants always involve precise (and hence gradual, non-ballistic) positioning of the articulator. When the articulator is the dorsum, a vowel-rhotic sequence, like diphthongs, is essentially transitional, but (unlike diphthongs) lacking a phonemic status.

For the general a-typicality of pre-sonorant vowel quality as a result of regressive co-articulatory effects see e.g. Guenther et al. (1999).

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The blurring effect of sonorants (2) Regressive co-articulatory colouring effects of sonorants - illustrations

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The blurring effect of sonorants (3) Backward masking effect on a preceding vowel

(a) Introduction to backward masking

Auditory backward masking – interference of a consecutive sound (masker) in the perceptual processing of the auditory cues of the preceding sound (target), e.g. Massaro (1972,1973).

The experimental correlate of masking is degraded performance in target detection/identification tasks as a function of masker introduction.

Simple illustration with tone recognition:

Three tones to remember: low, mid & high

Which tone is this one? …this one? …and this one?

Now listen to a tone followed by random noise. Which tone is this one?

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(b) Properties enhancing backward masking:

•Loudness of the masker (softness of the target), e.g. Repp (1975).Compare:

•Length of the masker (shortness of target ), e.g. Repp (1975).Compare:

•Immediate adjacency of the masker to the target, e.g. Homick et al. (1969).Compare:

•Categorical auditory similarity of masker and target, e.g. Loeb&Holding (1975), unless, of course, the target and the masker are identical, e.g. Repp (1975).Compare:

•Inventory and auditory density of possible targets, e.g. Dorman et al. (1977).

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(c) Sonorants ‘optimally’ backward-mask vowels, because …

•Sonorants are louder than obstruents, e.g. Fletcher (1953:84-86)

•Sonorants (like fricatives) are auditorily continuant – they do not involve initial silence (like stops or affricates).

•Sonorants are categorically similar to vowels – the auditory image of both is formant-based, e.g. Tarnóczy (1948), Boersma (1998:18).

But … sonorants are typically short, compared to obstruents.

Yet … what if the sonorants are lengthened (e.g. geminates)…?

Hypothesis:

Compared to other sounds (obstruents), sonorants (nasals, liquids, glides and vowels), have significantly greater potential for backward masking immediately preceding vowels, especially when the sonorant is lengthened and the target vowel is short.

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Phonetic features of Early Modern Gaelic straightforward reconstruction according to shared features of

modern spoken dialects of Irish and Scottish Gaelic

(1) Consonants

Notice:•Secondary articulation: ‘slender’ (palatalised) vs. ‘broad’ (velo-uvularised).

•Multiple contrasts among coronal sonorants.

•Aspiration of voiceless stops.

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Phonetic features of Early Modern Gaelic(1) Consonants

(a) Robust secondary articulation: Following shortening of certain diphthongs by clipping their initial part in Middle Gaelic, allophonic co-articulation becomes phonemic secondary articulation (McManus 1994).A consonant is either palatalised or velo-uvularised (as in e.g. Russian), and co-articulatory effects of a following vowel are blocked, e.g. Ní Chiosáin & Padgett (2001). Hence, the acoustics of the consonant and the transition do not cue to the quality of the following vowel.Notice the long transition during the vowels after secondarily articulated [l]:

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(b) ‘Lax/tense’ contrast among coronal sonorants: Lax (historically singleton) coronal sonorants involve unmarked articulation, while their tense (historically geminate) correlates involve large surface contact (+distributed) and peripheral placement of the primary articulator, e.g. Quiggin (1906), Mhac an Fhailigh (1968).

Examples with the laterals are:

The time-costliness of the marked gestures of the tense coronal sonorants make them inherently longer than their lax counterparts, while the labial and dorsal nasals are presumably in between, duration-wise.

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(c) Aspiration of voiceless stops: Voiceless stops are both pre- and post-aspirated, with partial devoicing effects on adjacent vowels and sonorants, e.g. Ní Chasaide (1999). The devoiced portion of a sonorant is merely a ‘mellow’ voiceless fricative, with very limited intensity.Compare:blaosc 'shell' [] vs. pléasc 'explosion‘ [l]borb 'fierce' [] vs. corp 'body' []seilg 'hunt' [] vs. dailc 'squat' []

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(c) Backward-masking potential of consonants in Gaelic: Following the principles of backward-masking, emphasising masker’s duration, intensity and categorical similarity to the target (slide no. 8 above), Gaelic consonants have backward-masking potential over preceding vowels, according to the following hierarchy:

Tense coronal sonorants []Non-coronal nasals and glides [m, m, , , j, w]

Lax coronal sonorants []Devoiced lax coronal sonorants []

Obstruents (voiced fricatives > voiceless fricatives > voiced stops > voiceless stops)

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Phonetic features of Early Modern Gaelicstraightforward reconstruction according to shared features of

modern spoken dialects of Irish and Scottish Gaelic (2) Vowels

(a) Scope - stressed short vowels:

Quantity was (and still is) contrastive, e.g.: caise ‘stream’ [] vs. cáise ‘of cheese’ []ciste ‘fund’ [] vs. císte ‘cake’ []

As long vowels are rather immune to blurring, our concern is with short vowels.

Furthermore, as quality contrast among short vowels was (and still is, in most

modern dialects) limited only to word-initially stressed syllable (e.g. McManus 1994), and as blurring of non-contrastive sounds is essentially ineffective, our focus is on word-initial, stressed short vowels only.

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Phonetic features of Early Modern Gaelic(2) Vowels

(b) Features of stressed short vowels:• Grammatical (‘phonemic’) contrast is limited to a ternary height parameter (high, mid

& low), e.g. Ní Chiosáin (1991). • The degree of frontness is determined by the secondary articulation of the surrounding

consonants. Lip-rounding is determined by a combination of vowel height and both primary and secondary articulation of the surrounding consonants. Both features are therefore non-contrastive.

• Nevertheless, there is great auditory diversity, spanning most of the vocalic space (e.g. Sommerfelt 1922 mentions 20 different qualities of short vowels).

Examples:

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Vocalic Alternations in Contemporary Irish

1. Lengthening of a stressed short vowel before a non-lax sonorant in coda:singular pluralcam ‘fraud’ [] *[] cama [] *[ ] faill 'opportunity‘ [] *[] failleannaí [] *[]… but not if the sonorant is lax or if the vowel is long or if the vowel is unstressed:fail 'hick-up' [] faileannaí []fáil 'receiving‘ [] fáileachaí []gradam ‘award’ [] *[]capaill 'horses' [] *[]

2. Lengthening before a lax coronal sonorant followed by a coronal other than [t]:ard 'high' [ *[]art 'on you' []

3. Epenthesis between a lax coronal sonorant and a non-coronal other than a voiceless stop, after a short vowel:tairbh ‘bulls’ [] *[] tairg ‘offer (v.)’ [] *[]táirg ‘produce’ []toirc ‘boars' [ ]

For evidence of the productiveness of these lengthening and epenthesis alternations see Becker (2003:68-75).

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Vocalic Alternations in Early Modern Gaelic

A stressed short vowel becomes half-long before any sonorant in coda unless the sonorant is lax and is word final or followed by a (pre-aspirated) voiceless stop. E.g. (a) faill 'opportunity‘ [] cam ‘fraud’ []

(b) tairbh ‘bulls’ [] ard ‘high’ []According to Greene (1952), the second environment gave rise to epenthesis of a copy vowel into the cluster, rather than lengthening. At least perceptually this copy vowel did not introduce another syllable, as is known to be the case of modern instances of this epenthesis in Scottish Gaelic (e.g. Watson 1994):tairbh ‘bulls’ [] ard ‘high’ [].In studies of backward masking, both target lengthening and recurrence (copying) are known to enhance target recognition.Claim: Half-long vowels / copy epenthesis were repair mechanisms used to overcome the crucial blurring effect of sonorants in Gaelic.

The emergence of half-long vowels, e.g. McManus (1994):

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Vocalic Alternations in Early Modern Gaelic The emergence of half-long vowels / copy-epenthesis

This lengthening / epenthesis process did not affect:

• Long vowels, which are immune to blurring due to their inherent length. • Unstressed (non-contrastive) short vowels, because blurring is essentially ineffective

when the target is non-contrastive.• Short vowels in open or ‘half-open’ syllables. The split of syllabic domain reduces

regressive co-articulatory effects, and possibly also reduces auditory association of the target and the masker.

• Short vowels followed by a devoiced sonorant. Auditorily, the sonorant becomes a soft fricative, and loses most of its masking potential.

• Short vowels in monosyllabic words with a lax sonorant as a simple coda, e.g. col ‘prohibition’ []. Gaelic is a ‘stress-timing’ as well as stress-initial language. It is plausible that such short monosyllabic words are automatically lengthened in order to increase the period of time until the next stressed syllable (the initial syllable of the following word). In Donegal Irish, the only modern dialect which has ‘syllable timing’ (Ní Chasaide, pc.), a lax sonorant in such words is devoiced (e.g. Ní Chasaide 1979): []. Compare:

ngael ‘of Gaels’ [] vs. geal ‘clear’ []sról ‘satin’ [] vs. scoil ‘school’ []

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The Blurring Effect - Experimental Validation(1) Hypotheses

General hypothesis: Perception of vowel quality is degraded by the presence of a following sonorant, as a combination of regressive co-articulatory colouring effects unique to sonorants and backward masking. The case of regressive colouring is well established, and the current study focuses on the effect of backward-masking on vowel perception.

Further operational hypotheses concerning backward masking:

• In an identification task, a pre-sonorant vowel should be identified less adequately than a pre-obstruent vowel, all else being equal (no co-articulatory effects, identical pitch, acoustics, duration and intensity).

• Lengthening a pre-sonorant vowel should improve its perception.

• Devoicing a sonorant should improve the perception of a preceding vowel.

• Lengthening the sonorant should degrade the perception of a preceding vowel (not studied here).

With particular reference to Irish, co-articulatory effects of vowels on adjacent consonants should be neutralised, and correct vowel identification is determined by height identification.

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The Blurring Effect - Experimental Validation(2) Stimuli

The stimuli are nonsense monosyllables of the form [dVC]. They were recorded and constructed using PRAAT, as follows:

• A reference monosyllable [] was recorded with level pitch p and vowel kernel amplitude a. The onset together with the first two voicing cycles of the vowel were extracted to yield a constant onset and transition (all signal truncations here and elsewhere were performed at zero-crossings in the steep rising of a voicing cycle).

• The vowels [] were recorded with p in environment [d_]. Their kernels were then normalised to a. The high and low vowels were then slightly attenuated and amplified, respectively, as best compromise between natural relative amplitude and experimental comparability. Then kernels with c-1, c and c+1voicing cycles were extracted, for high, mid and low vowels respectively, again as best compromise between natural relative duration and experimental comparability.

• The codas [p t k b d g f s v z m n l r ] were recorded with roughly identical duration d in environment [_] with p. [] kernels were equalized to a, thus obtaining representative relative intensities amongst the various codas. Codas were extracted together with the last two cycles of the preceding vowel.

• All combinations of common onset + vowel + coda were concatenated to yield naturally sounding, co-articulation-free [VC] tokens.

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The Blurring Effect - Experimental Validation(2) Stimuli

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The Blurring Effect - Experimental Validation(3) Method

(a) Subjects: About 40 first-year students of linguistics, most of whom speakers of Hiberno-English (importantly: no native speaker of Irish), with a few weeks experience in phonetic transcription.

(b) Task: Passive (multiple choice) phonetic transcription of the vowels in the stimuli.

(c) Procedure: An experiment recording consisted of a sequence of n blocks of 8 stimuli-tokens, in random order (adjacent tokens never contained the same vowel). Dummy tokens padded the beginning and end of the recording. Between-block interval was 7.2s and between-token interval was 2.8s. A brief order announcement preceded each block and token. The digital master-recording was rendered onto analog tapes. The subjects, seated in separate booths, listened to the tapes via earphones at a comfortable level and could neither stop nor rewind the tapes. Upon hearing a stimulus, the subject, faced with the IPA symbols {}*, circled the one matching the vowel she heard, in the appropriate cell in the provided answering sheet. No performance feedback was given at any stage.

(d) Evaluation: A given stimulus transcription was evaluated as correct if the height of the transcribed vowel matched the height of the vowel contained in the stimulus. Height mismatch or blank cell were evaluated as incorrect. Subjects with extremely good performance and subjects with near (or below) random performance were dropped in order to avoid ceiling and random-noise effects, respectively.

* Why was included? Perception-grammar… Anyway, it was evaluated exactly like .

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The Blurring Effect - Experimental Validation(4) Experiment 1: Sonorants vs. fricatives vs. stops – statistic parameters

Stimuli: {,}x{p,t,k,b,d,g,f,s,,v,z,,m,n,,l,r,,no-coda}+6 dummies = 120 stimuli.

Auditory classes: stop {(p,t,k),(b,d,g)}, fricative {(f,s,),(v,z, )}, sonorant {(m,n,),(l,r,)}Removal of side-effects:

[]-data was dropped due to a clear ceiling effect (almost all subjects had near-perfect recognition results for this vowel, probably because of the substantial experience subjects had with this vowel in their phonetics lab sessions. It is also likely that the double centre-of-gravity effect of high front vowels (F0+F1, F2+F3+F4), contribute to the relatively stable auditory image of this vowel and ‘immune’ it against masking (e.g. Stevens 1998:266-268).As for the rest of the data, 3 out of the 36 subjects were dropped due to ceiling effect (above 85% correct). 14 subjects were dropped due to random-noise effect (below 45% correct). No other sounds or subjects systematically twist the results.

Statistics after removal of side effects:

Subjects: 19, Tokens: 95 (including 5 no-coda tokens)

Answers: per coda: 95, per auditory class: 570, per auditory sub-class: 285per class per subject: 30, per sub-class per subject: 15

Correct answers for no-coda stimuli (can be taken as default vowel recognition for this subject population at these experiment conditions): 56 (58.9%).

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The Blurring Effect - Experimental Validation(4) Experiment 1: Sonorants vs. fricatives vs. stops - results

Vowel recognition across coda consonants

010203040506070

stop-vls stop-vcd fric-vls fric-vcd son-nas son-orCoda Class

% C

orre

ct

Vowel recognition across coda classes

0

10

20

30

40

50

60

70

Stop Fricative SonorantCoda Class

% C

orre

ct

St-vlsSt-vcdFr-vlsFr-vcdSon-nasSt-vcd0.344Fr-vls0.50.368Fr-vcd0.1340.3250.208Son-nas0.0130.0440.0210.072Son-or0.0020.0100.0050.0110.177

Significance tests across coda classes:Assuming default recognition probability per token is 0.589, cumulative z-scores are: Stops: p=0.448 Fricatives: p=0.289 Sonorants: p<0.000001voiceless: p=0.57, voiced: p=0.38 voiceless: p=0.57, voiced: p=0.18 nasal: p<0.002, oral: p<0.0001

Significance tests across subjects (no default recognition probability assumed):One-tailed matched-pair t-test cumulative p-scores (on correct answers per coda class):

StopFricFric0.366Son0.0030.004

Both tests indicate that the results are significant both at auditory class and sub-class level, and confirm the hypothesis that vowel recognition is degraded by the presence of a following sonorant – vowels are backward-masked (only) by sonorants.

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The Blurring Effect - Experimental Validation(5) Experiment 2: the effects of vowel lengthening and syllabic split

Additional stimuli: This experiment used the sonorant-coda stimuli of ex. 1 ([]-tokens were dropped), together with two parallel sets. For each [dVC] token two parallel tokens were constructed: (a) A token with a longer vowel (the same vowel kernel was used, but the middle voicing cycle was reduplicated as needed). These longer vowels had c+1, c+2 and c+4 voicing cycles for high, mid & low vowels respectively. (b) A token in which the sonorant is slightly shortened and released into [] (The sonorant was recorded in environment [d_] with p and equalised to a as in ex.1. Then the final portion of the sonorant together with the release into the following [] were truncated and concatenated to the [dVC] token in the middle of the coda. A constant unstressed final [] was concatenated to all tokens at the end).Thus {[dVC], [dVC], [dVC]} triplets were obtained, e.g.Admittedly, the [dVC] did not sound very natural, and this might affect the results.The stimuli were randomized as in ex.1

Parameters:Stimuli: {}x{m,n,,l,r,}x 3 conditions + 6 dummies = 96 stimuliRemoval of side effects: 2 out of the 36 subjects were dropped due to ceiling effect (above

85% correct). 17 other subjects were dropped due to random-noise effect (below 45% correct).

Answers: per token: 17, per sonorant: 255, per condition: 510,per condition per sonorant: 85, per condition per subject: 30

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The Blurring Effect - Experimental Validation(5) Experiment 2: vowel lengthening and syllabic split - results

0

10

20

30

40

50

60

70

Consonant

% C

orr

ect

dVCdV'CdVC@

Significance tests across token triplets:

One-tailed matched-pair t-test cumulative probabilities (on correct answers per tokens):[dVC]/[dVC]: 0.198 [dVC]/[dVC]: 0.049 [dVC]/[dVC]: 0.221Significance tests across subjects:Two-tailed matched-pair t-test cumulative probabilities (on correct answers per condition):

[dVC]/[dVC]: 0.165 [dVC]/[dVC]: 0.006 [dVC]/[dVC]: 0.192 The tests indicate that the results are significant for the [dVC]/[dVC] condition, while the tendency for the [dVC]/[dVC] condition is not significant. Therefore, the results confirm the hypothesis that lengthening enhances vowel recognition. Hence, vowel lengthening is an appropriate repair mechanism for overcoming backward masking.

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The Blurring Effect - Experimental Validation(6) Experiment 3: the effect of sonorant devoicing

Stimuli: This experiment used the sonorant-coda stimuli of ex. 1, together with a parallel set of stimuli, containing the corresponding [dVC] (the coda sonorant in such tokens has the same duration and its latter half is voiceless). E.g.The stimuli were randomised as in the previous experiments.

Parameters:Stimuli: {}x{(m,n,,l,r,),(,,)} + 4 dummies = 64 stimuliRemoval of side effects: 2 out of the 36 subjects were dropped due to ceiling effect

(above 85% correct). 17 other subjects were dropped due to random-noise effect (below 45% correct).

Answers: per token: 15, per sonorant: 225, per voicing condition: 450 per condition per sonorant: 75, per condition per subject: 30

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The Blurring Effect - Experimental Validation(6) Experiment 3: the effect of sonorant devoicing - results

0

10

20

30

40

50

60

70

80

Consonant

% C

orr

ect

voiced

devoiced

Significance tests (One-tailed matched-pair t-test cumulative probabilities ): Across token pairs (on total correct answers per parallel tokens): 0.038Across subjects (on subjects’ correct answers per voicing condition):0.030Both tests indicate that the results are nearly significant, supporting the hypothesis that devoicing reduces the backward-masking effect of a sonorant on a preceding vowel and thus improving vowel recognition.

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The Blurring Effect - Experimental Validation(7) Commentary on the experiments

• The lexical status of tokens was not taken into account. Familiarity with a lexical item (e.g [dk] [dan] compared to [dg], [dar]) enhances the recognition of a corresponding stimulus, e.g. (Walley&Flege 1999). This could have been prevented, by e.g. using an any ungrammatical onset ([x,] etc.). Nevertheless, lexical status of tokens had no effect on the variables under question, and at least the high recognition results for [dV]-tokens indicate that lexical status had only marginal effect here, if at all (in English, [ ] is an ungrammatical coda after short vowels, and an extremely rare coda otherwise).

• The effect of coda consonant on vowel duration was not taken into account. In English (e.g. Peterson&Lehiste 1960), vowel duration is a function of the following coda hierarchy: stop-vls << stop-vcd < fric-vls < son << fric-vcd < [].Nevertheless, the vowel in the stimuli were always ‘ungrammatically’ extra-short, biasing similarly against all coda classes except for voiceless stops. Finally, the predicted strong duration bias against [dV]-tokens is unattested in the results.

• The absence of co-articulatory effects characteristic of post-vocalic sonorants makes the sonorant-final stimuli more unnatural than obstruent-final stimuli. Unfortunately, removing co-articulation is essential for testing the backward masking hypothesis, because degraded recognition performance can always be attributed to the presence of co-articulatory effects. However, in ex. 3, the absence of such effects is equally unnatural, while the results are nevertheless significant.

• A series of similar pilot experiments was conducted a year earlier, producing practically the same results (Becker 2003). While those earlier experiments lacked consistent and careful design, the repetition of the results indicate that the findings are reliable.

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ReferencesBecker, R. (2003) The Blurring Effect of Sonorants and Vocalic Alternations in Irish. MA Thesis. Dublin: University College Dublin.Boersma, P. (1998) Functional Phonology. The Hague: Holland Academic Graphics.Dorman, M., D. Kewley-Port, S. Brady & M. Turvey (1977) 'Vowel recognition, inferences from studies of forward and backward masking'. Quarterly Journal of Experimental Psychology 29:483-497.Fletcher, H. (1953) Speech and Hearing in Communication. Lancaster, PA: Lancaster Press Inc.Greene, D. (1952) 'Middle Quantity in Irish'. Ériu 18:108-112.Guenter, J., J. Lewis & M. Urban (1999) 'A perceptual study of vowels before /r/', in Proceedings of the Fourtienth International Congress of Phonetic Sciences.Homick, J., L. Elfner & G. Boothe (1969) 'Auditory temporal masking and the perception of order'. Journal of the Acoustical Society of America 45:712-718.Johnson, K. (1997) Acoustic & Auditory Phonetics. Cambridge, MA: Blackwell Publishers.Liberman, A., F. Cooper, D. Shankweiler & M. Studdert-Kennedy (1967) ‘Perception of the speech code’. Psychological Review 74:431-461.Loeb, M. & D. Holding (1975) 'Backward interference by tones or noise in pitch perception as a function of practice'. Perception and Psychophysics 18:205-208.Massaro, D. (1972) 'Perceptual images, processing time and perceptual units in auditory perception'. Psychological Review 79:124-145.Massaro, D. (1973) 'A comparison of forward versus backward recognition masking'. Journal of Experimental Psychology 100:434-436.McManus, D. (1994) 'Classical Modern Gaelic', in Stáir na Gaeilge (eds. McKone, K., D. McManus, C. Ó Háinle, N. Williams & L. Bratnach), 336-446. Maynooth: Coláiste Phádraig. (in Irish).Mhac an Fhailigh, E. (1968) The Irish of Erris, Co. Mayo. Dublin: Dublin Institute for Advanced Studies.Ní Chasaide, A. (1979) 'Laterals of Gaoth Dobhair Irish and Hiberno English', in Occasional Papers in Linguistics and Language Learning 6:54-78.Ní Chasaide, A. (1999) 'Irish', in The Handbook of the International Phonetic Association. Cambridge: Cambridge University Press.

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References (cont.)Ní Chiosáin, M. (1991) Topics in the Phonology of Irish. PhD Dissertation. Amherst, MA: University of Massachusetts.Ní Chiosáin, M. & J. Padgett (2001) 'Markedness, segment realization and locality spreading', in Segmental Phonology in Optimality Theory (ed. Lombardi L.). Cambridge: Cambridge University Press.Peterson, G. & I. Lehiste (1960) 'Duration of syllable nuclei in English'. Journal of the Acoustical Society of America 32:693-703.Quiggin, E. (1906) A Dialect of Donegal. Cambridge: Cambridge University Press.Repp, B. (1975) 'Dichotic masking of consonants by vowels'. Journal of the Acoustical Society of America 57:724-735.Sommerfelt, A. (1922) The Dialect of Torr, Co. Donegal. Christiania: J. Dybwad.Sproat, R. & O. Fujimura (1993) Allophonic variation in English /l/ and its implications for phonetic implementation. Jounal of Phonetics 21:291-312.Stevens, K. (1998) Acoustic Phonetics. Cambridge, MA: MIT Press.Tarnóczy, T. (1948) 'Resonance data concerning nasals, laterals and trills'. Word 4:71-77.Walley, A. & J. Flege (1999) 'Effects of lexical status on children's and adults' perception of native and non-native vowels'. Journal of Phonetics 27:307-332.Watson, S. (1994) 'Scottish Gaelic', in Stáir na Gaeilge (eds. McKone, K., D. McManus, C. Ó Háinle, N. Williams & L. Bratnach), 661-702. Maynooth: Coláiste Phádraig. (in Irish).Wright, J. (1986) 'The behaviour of nasalized vowels in the perceptual vowel space', in Experimental Phonology (eds. Ohala, J. & J. Jaeger), 45-68. London: Academic Press Inc.

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