On the Difficulty of Defining “Difficult” in Second-Language Vowel Acquisition

Abstract

Hierarchies of difficulty in second-language (L2) phonology have long played a role in the postulation and evaluation of learning models. In L2 pronunciation teaching, hierarchies are assumed to be helpful in the development of instructional strategies based on anticipated areas of difficulty. This investigation addressed the practicality of defining a pedagogically useful hierarchy of difficulty for English tense and lax close vowels (/i I u ʊ/) produced by Cantonese speakers. Unlike their English counterparts, Cantonese close tense-lax pairs are allophonic variants with [i u] occurring before alveolars and [I ʊ] before velars. Each tense-lax pair represents a “phonemic split” in which members of a single L1 category are realized contrastively in L2. Despite evidence that English tense-lax distinctions are challenging for Cantonese speakers, no previous empirical work has closely considered the problem from the standpoint of vowel intelligibility across multiple phonetic contexts and in different words sharing the same rhyme. In a picture-based word-elicitation task, 18 Cantonese-speaking participants produced 31 high-frequency CV and CVC words. Vowels were evaluated for intelligibility by phonetically-trained judges. A series of mixed-effects binary logistic models were fitted to the scores, with vowel quality, phonetic context (rhyme) and word as factors, and length of Canadian residence and daily use of English as co-variates. As expected, the general hierarchy of difficulty for vowels that emerged (/i/ > /u/ > /ʊ/ > /I/) was complicated by large differences across phonetic contexts. Results were not readily explicable in terms of transfer; moreover, different words with the same rhyme were not produced with equal intelligibility. The most serious modeling complication was the sizeable inter-speaker variability in difficulties, which could not be accounted for by model co-variates. Although some difficulties were roughly systematic at the group level, it is argued that establishing a pedagogically useful hierarchy on such data would prove intractable. Rather, L2 learners might be better served by assessment and instructional targeting of their individual problem areas than by a focus on errors predicted from hierarchies of difficulty.

Variability in L2 Vowel Production: Different Elicitation Methods Affect Individual Speakers Differently

“…Moreover, different speakers with approximately the same AOL, and similar L2 experience, varied in the number of the 11 target vowels they produced intelligibly, with some producing as few as six and others producing all 11 intelligibly. This led Munro et al ( 1996 , p. 332) to observe that “between-vowel effects did not occur uniformly for all, or even for a large majority, of the learners.” Such variability, as well as the parallel lack of uniformity in Munro ( 2021 ), does not appear explicable in terms of aptitude, motivation, or quantity of general L2 experience. In particular, there is no obvious reason why such characteristics should lead one speaker to produce good exemplars of / I / in hit , but mostly unintelligible productions of the same vowel in sit , while another speaker shows the opposite pattern.…”

“…The degree to which Cantonese and other learners of English diverge from one another in their success in high vowel production had received little attention until recently. Using speech elicited in a picture-naming task, Munro ( 2021 ) observed considerable interspeaker variability in the vowel intelligibility of Cantonese speakers when productions were considered in terms of vowels alone, vowels in rhymes, and even vowels within particular words. In this follow-up study, the Munro ( 2021 ) investigation is extended to compare the effect of two speech elicitation techniques, one with and one without an audio prompt, on interspeaker variability.…”

“…Using speech elicited in a picture-naming task, Munro ( 2021 ) observed considerable interspeaker variability in the vowel intelligibility of Cantonese speakers when productions were considered in terms of vowels alone, vowels in rhymes, and even vowels within particular words. In this follow-up study, the Munro ( 2021 ) investigation is extended to compare the effect of two speech elicitation techniques, one with and one without an audio prompt, on interspeaker variability. The method of elicitation is important because accurately assessing learner difficulties is fundamental to both pedagogy and theory-building.…”

“…Although that opinion was disputed long ago (Walz, 1980 ), interest among teachers in error prediction has persisted (Munro, 2018 ; Rehman et al, 2020 ). Recently, Munro et al ( 2015 ) and Munro ( 2018 , 2021 ) discussed evidence that individual variability in L2 production, even among speakers of a shared L1, is greater than has sometimes been assumed. Although it may be possible to offer broad, probabilistic error hierarchies for groups of learners from particular backgrounds, such predictions often do not apply to all, or even to the majority, of learners.…”

Commentary: When the Easy Becomes Difficult: Factors Affecting the Acquisition of the English /iː/-/ɪ/ Contrast and On the Difficulty of Defining “Difficult” in Second-Language Vowel Acquisition

“…This is in part because a satisfactory method for measuring interactions between first language (L1) and L2 sound categories remains elusive (Flege and Bohn, 2021). Cebrian et al (2021) and Munro's (2021) contributions to the Frontiers' Research Topic "L2 Phonology Meets L2 Pronunciation" evidence the effect of this persistent methodological concern. Both also reveal that generalizations based on group means are problematic, and that many complexities that emerge in L2 speech research are attributable to individual differences across learners, independent of their L1.…”