20Q: Accents and Accent Modification

From the Desk of Ann Kummer

Imagine that you are a brilliant scientist who has been recruited to the United States to work with other brilliant scientists who have the same interests and goals. This new job requires you to collaborate daily with your colleagues and to attend conferences where you present papers on the podium. This is all very exciting. However, your native language is Korean, and you have a heavy accent when speaking English. Unfortunately, your accent makes it hard for others to understand you. At the Cincinnati Children’s Research Foundation (which is one of the top pediatric research facilities in the country), we have had many researchers with this problem. As such, the Division of Speech-Language Pathology developed an Accent Reduction Program to increase the intelligibility of researchers who spoke English as a second language.

I was able to witness firsthand how an accent reduction program can increase a speaker’s intelligibility and thus confidence in speaking English. I have no doubt that this also had an effect on the students’ success. Therefore, I’m happy that so glad that Robert (Bob) McKinney agreed to submit this 20Q article accents and accent reduction.

By way of introduction, Robert (Bob) McKinney, M.A., CCC-SLP is the author of “Here’s How to Do Accent Modification” published by Plural Publishing in 2019. He holds MAs in Communicative Disorders, International Relations, and Education. Bob speaks six languages and has worked with clients from over eighty countries. He currently works with predominantly bilingual students as the lead SLP at the Sweetwater Union High School District. At San Diego State University, he teaches phonetics and supervises graduate students in the Accent and Communication Training Program. He has served as the president of the Corporate Speech Pathology Network (CORSPAN) and on the board of directors of the California Speech-Language-Hearing Association (CSHA).

In this article, Bob explains how speech-language pathologists are uniquely suited to help adults with accents become more effective communicators in their new language. This article also provides insights into the nature of non-native accents and outlines best practices in the ethical provision of elective accent modification services.

Now…read on, learn, and enjoy!

Ann W. Kummer, PhD, CCC-SLP, FASHA, 2017 ASHA Honors
Contributing Editor 

Browse the complete collection of 20Q with Ann Kummer CEU articles at www.speechpathology.com/20Q

20Q: Accents and Accent Modification

Learning Outcomes

After this course, readers will be able to: 

• Describe the nature of non-native accents and their potential impact on communication and wellbeing
• Identify the roles of accentedness, intelligibility, comprehensibility, and naturalness in accent modification
• Describe best practices for providing ethical elective accent modification services

Robert McKinney

1. What is an accent?

That sounds like it should be an easy question to answer, but accents and attitudes about them represent incredibly complex phenomena. In a basic sense, we can say that accents are what make us sound similar to (or different than) other speakers of the same language. In terms of formal definitions, the word accent tends to be interpreted in two different ways. Crystal (2008, p.3) defined accent broadly as the “features of pronunciation which identify where a person is from, regionally, and socially,” but Scovel (1969, p. 38) defined it in the narrower sense as “phonological cues…which identify the speaker as a non-native user of the language.” The logic of the broad definition should be clear to anyone with an understanding of linguistics, but the narrow definition is much more commonly used, and this is important. According to the broad definition, everyone has an accent in any language they speak, including their mother tongue. By the second definition, depending on the language in question, some speakers have accents and others don’t, and this division of the world into native and non-native speakers has profound implications.

2. What’s the difference between a dialect and an accent?

Students of linguistics quickly discover that the word “dialect” is notoriously difficult to define, and there is no clear dividing line between languages and dialects. We generally understand dialect to mean a version of a language that can vary in terms of phonology, syntax, and semantics, among other factors, but is still mostly understood by other speakers of that language. Accent is a narrower term since it is tied so closely to phonology alone. For the rest of my answers, I’ll be focusing on the accents of non-native speakers and not those of non-mainstream dialect speakers even though there is overlap in many areas including the linguistic discrimination that both groups may face.

3. Why do people have accents?

That’s a great question, and I wish I had an easy answer. Accents tend to be highly noticeable, and it’s natural to wonder why they exist. It’s likely that from the very emergence of language, humans have been aware that speakers sound different depending on whether they learned a language as a child or an adult, but we still do not know exactly why. Research has demonstrated differences for childhood and adult acquisition of  vocabulary, grammar, pronunciation, and many other aspects of language, and this is often referred to as the Critical Period Hypothesis (CPH). Studies consistently show a strong critical (or sensitive) period for acquiring the phonology of a second language, which means that a child immersed in a new linguistic environment will tend to sound indistinguishable from native speakers in a relatively short time while adults acquiring a new language will almost always sound different, regardless of the amount of exposure they have. Recent research has focused on neurobiological explanations for this, but the precise mechanism has not been established to date. Perhaps the most important “take home” from this is that it is normal and natural for adults acquiring a second language to sound different from native speakers.

4. Can non-native speakers “lose” their accent?

This question comes up very often, so it is obviously on many people’s minds. We know from the broad definition of accent that everyone has one, so the term “lose” doesn’t really make sense if we look at accents that way, but the idea behind it is whether an adult acquiring a language can ever sound indistinguishable from someone who learned the same language as a child, and in research it’s often referred to as “ultimate attainment.” Many are surprised to learn that the best evidence shows this to be extremely rare if not impossible. For example, Abrahamsson and Hyltenstam (2009) studied 195 Spanish-Swedish bilinguals who self-identified as having native Swedish accents and found that none of the speakers who acquired Swedish after age 17 were able to pass as native speakers after careful examination, concluding that “absolute nativelikeness in late learners, in principle, does not occur.” Many anecdotal reports of adult language learners sounding exactly like native speakers do not hold up to rigorous scrutiny or overlook significant childhood exposure. While it is certainly possible for some adult language learners to “pass” for native speakers under certain conditions, the short answer to the question above is “no”. This underscores the importance of the idea that accents are normal and natural for adults who learn a new language.

5. What about actors and spies? Can’t they learn to sound exactly like native speakers?

In virtually every profession, if a speaker communicates effectively, there is no reason for the presence of a non-native accent to affect workplace performance in any way, but there are two professions in which even a trace of an accent might cause significant difficulties: acting and undercover spying. Actors work hard to create the illusion that they are someone else, and the way their character sounds helps maintain the suspension of disbelief. In a similar vein, but with higher stakes, deep cover spies or “moles” need to convince others that they are part of the very societies they are working against, and a non-native accent might betray them. While there are many actors who are able to successfully imitate a wide variety of regional or social dialects of the same language, it is very rare for non-native speakers to attempt this. For example, Hugh Laurie, who is originally from the United Kingdom and normally speaks with an English accent, played an American character successfully for eight seasons on the television series House, but it would be impossible for him to portray a native Parisian speaking French in a way that would go unnoticed by speakers of that language. Despite the number of highly talented actors around the world, there are only a handful who have ever portrayed native speakers in a language they didn’t speak as children. Incidentally, these exceptions almost always come from speakers of closely related languages, so for English, these actors tend to speak fellow Germanic languages such as Swedish or Dutch. In espionage, the story is the same. Although it’s a common plot point in spy movies, there are extremely few (if any) documented cases where an undercover agent was able to pass for a native of a language they acquired as an adult (McKinney, 2019).

6. Do speakers have to sound non-native to communicate effectively?

No, not at all! Many non-native speakers communicate more effectively than native speakers all over the world. So far we have been focused on demonstrating that it is completely natural for adults acquiring a new language to sound different, and now we can see why that doesn’t need to affect communication. While we may virtually never encounter non-native adults who sound exactly like natives, non-natives who are highly effective communicators in their new language are all around us. To understand why this is true, we can look to the pioneering work of Munro and Derwing (1995), who demonstrated that we can analyze non-native speech in terms of  the interplay of three factors: accentedness, intelligibility, and comprehensibility. In this paradigm, “accentedness” refers to what makes someone sound different, “intelligibility” is how much we can understand, and “comprehensibility” is our ease of understanding. This three-way split allowed them to demonstrate that there is no direct connection between accentedness and intelligibility. In other words, a speaker can be rated as sounding noticeably very different and still be understood 100% of the time. This is extremely important because it demonstrates that accent itself does not have to affect the sharing of ideas, while by definition, intelligibility does. Munro and Derwing also sought to look beyond intelligibility, and they  promoted the idea of “comprehensibility” to show that ease of understanding plays a role in a listener’s ability to focus on a speaker’s message. In my own work, I argue that “naturalness” might be a better way to describe this since it is a concept familiar to SLPs who work in areas such as fluency, dysarthria, and alaryngeal speech. Natural speech fits within a range of speech patterns at the segmental and suprasegmental level that are common to speakers of the language.

7. How can an accent affect someone’s communication and wellbeing?

Unfortunately, speakers who sound different often face a number of challenges, including significant linguistic discrimination. In terms of communication, speakers who are unintelligible may have difficulty conveying their ideas successfully, but even highly intelligible speakers can face discrimination ranging from subtle bias to outright harassment. Lev-Ari and Keysar (2010) demonstrated that statements read by non-natives were deemed less credible than those read by natives, even when judges were explicitly told that the statements did not originate with the speakers. Remarkably, Hanzlíková and Sarnitzl (2017) found this same effect for non-native judges. Many non-native speakers report a belief that their accent interfered with their ability to get a job, and unfortunately, there is evidence bearing this out. Munro (2003) found instances of employment and housing discrimination, as well as harassment, based on accent in a review of human rights cases in Canada. In addition, non-native speakers often report fears that they will not receive promotions as readily as their native-speaking colleagues. Fuertes and colleagues (2012, p. 130) wrote, “evaluations based on accent appear to have a significant impact on individuals who do not speak with standard accents and are likely to lead to discrimination and possibly other severe social consequences.” In addition, many non-natives report that when they speak in their second language, they feel like they are wearing a mask, and that it is impossible to convey their true identity. Stigmatization can cause feelings of otherness, isolation, and a lack of confidence. In our own field, we must recognize the barriers non-native speakers face in entering our profession. We need as many non-native speakers in our field as possible, so it is important to value their ability to work with clients effectively in more than one language, and we should be mindful of the obstacles they face.

8. What options are available to promote successful communication between native and non-native speakers?

Successful communication is a shared responsibility, so listeners and speakers both need to make an effort to connect and share ideas. It’s important for monolingual native speakers to understand the work that goes into acquiring another language as an adult and to respect speakers who can communicate in more than one language. In some cases, listeners with little exposure to different ways of speaking may have a harder time understanding non-natives and could benefit from practice or listener training. In other cases, a lack of effort on the part of the listener may be a form of linguistic discrimination. On the other hand, mastering the phonology of a new language is a part of all language learning, so it would be unrealistic to expect non-native speakers acquiring a language to speak it intelligibly and naturally from day one. As learners acquire a new language they generally rely on a combination of practice, self-study, and direct instruction to communicate more effectively. Some learners opt for elective services to increase their proficiency in various aspects of the new language, and when this training is focused on oral language and provided by SLPs, it’s often called “accent modification.”

9. What exactly do you mean by accent modification?

Accent modification might be more accurately labeled as phonological instruction in a non-native language since it focuses on assisting language learners in acquiring the phonology of their new language. In its broadest form, it goes on in every language of the world when learners of all ages are developing their oral proficiency in a language other than their mother tongue. I’ve been a client of accent modification services myself both in the broad sense as I was learning the five languages I speak non-natively, and in the narrow sense, when I hired a trainer to work on my oral proficiency in Spanish before I began working with Spanish-speaking clients as an SLP in the public school system. Typical accent modification providers are language teachers, voice and speech trainers, and SLPs. Although many people assume that these services are always provided by native speakers of the “standard” dialect of the language in question, the reality is that services are provided by speakers of a wide variety of dialects as well as by non-native speakers. In fact, there is good evidence that non-native speakers are equal or better providers of these services because of their personal experience with language acquisition  (Levis, Sonsaat, Link, and Barriuso, 2016). Although SLPs are not the primary providers of these services, their background helps them excel in this subfield, and they generally provide these services through private practice or in university clinics.

10. What is the goal of accent modification?

In short, it’s effective communication. Accent modification providers help clients achieve their personal and professional goals by working with them on the way they speak in their non-native language.  Training may address intelligibility, naturalness, fluency, communication style, voice and resonance, or any number of additional areas necessary to share ideas successfully. Increasing clients’ awareness is fundamental because it improves listening skills and allows them to make more choices about their own communication. Despite the name, effective accent modification does not focus on the accent itself. Accents are a beautiful representation of the linguistic diversity of our species, and they can be separated from other factors such as intelligibility or naturalness that can affect communicative success.

11. If it’s not really about the accent, why not rename it?

ASHA uses the term “accent modification” and this is common among SLPs as well as clients. In the world of language teaching, it is usually called “pronunciation instruction.” Some terms that are still in use, such as “accent reduction,” have been criticized as potentially stigmatizing accents, and newer terms, including “intelligibility enhancement” and “accent expansion” have been proposed to replace them. It can be argued that any term using the word “accent” is to some extent a misnomer since best practices call for providers to focus on intelligibility, naturalness, and other factors that affect communication, and not the accent itself. It can be challenging to find a description that is both technically accurate and easily understood by the broader public, including potential clients. While the term “accent modification” is not perfect, it has several advantages: it is used by ASHA as well as many SLPs and clients, it’s relatively neutral sounding, and it highlights succinctly the focus on non-native speech. It’s also important to note that since we are working with differences and not disabilities, terms that medicalize non-native speech such as “treatment” or “therapy” should be avoided.

12. Do SLPs need additional training to do accent modification?

SLPs are communication experts, and it is a natural fit for us to work with clients on accent modification. The American Speech-Language-Hearing Association (ASHA) lists it twice in its Scope of Practice in Speech-Language Pathology (ASHA, 2016) — first in a list which includes the areas of practice traditionally associated with our field, and again under a shorter list of elective services, which includes professional voice use and transgender communication. You may hear some SLPs referring to being “certified” in accent modification, but they usually mean they took a course outlining a particular approach since no certification is provided by ASHA or required to work with clients in this subfield. The training SLPs receive gives them many advantages when working with non-native speech, but it is also important to be open to ideas that come from other fields and to spend some time becoming familiar with the aspects of accent modification that make it unique. ASHA’s Code of Ethics (ASHA, 2016) mandates that SLPs “shall engage in only those aspects of the professions that are within the scope of their professional practice and competence, considering their certification status, education, training, and experience,” so it is essential that SLPs devote time and energy to bridge any gaps in their knowledge and develop the skills necessary to become first-class practitioners in the field of accent modification if they offer that service.

13. What frameworks are most effective?

Accent modification services should be client-driven to focus on the personal goals and areas of need for each individual learner. The overarching goal is effective communication, so intelligibility tends to be prioritized to ensure that the speaker can be understood by the largest number of listeners possible. In addition, some highly intelligible speakers may use patterns that are so different from those used by most speakers of the language that listeners will focus on how something is said and not what the speaker is saying. I’m repeating myself here, but the accent itself does not need to be targeted, and clients should be assured that sounding different is entirely natural and can be a source of pride. Another useful framework is to view a client’s speech in terms of segmentals and suprasegmentals and balance training between these levels. The segmental level represents the individual sounds (phonemes and allophones) of the language, and clients may be better understood if they make changes in the way they produce certain sounds which may not exist in their language. The suprasegmental level refers to the larger patterns of speech, such as intonation and stress, that can impact naturalness as well as intelligibility. In addition, clients can be made aware of differences in communication styles (including gestures and body language), and they can be counseled about the linguistic discrimination they may face.

14. What ethical considerations are involved?

In the ESL world many years ago, there was a debate about whether it is more appropriate to focus on intelligibility versus native-like speech, and we now have over 25 years of evidence that intelligibility is key and that promoting the idea of sounding exactly like a native speaker is neither necessary nor helpful. In our own field, accent modification has often been misunderstood, and many SLPs report being discouraged from pursuing it by colleagues. Recently, some public criticisms, stemming predominantly from Critical Social Justice frameworks, have argued that accent modification does more harm than good by forcing non-natives to conform and perpetuating linguistic hierarchies that favor native speakers and mainstream dialects. Because these criticisms stemmed mainly from SLPs not practicing in this subfield or familiar with best practices, they tended to overlook the positive impact of effective practitioners as well as the desires of the clients. Of course, as in all areas of our field, some SLPs may stray from ethical practices, and it is important for all of us to collaborate in preventing this. In addition, many non-natives are inappropriately referred for accent modification, and this can be a devastating form of linguistic discrimination. The reality is that we live in a world where terrible discrimination exists, and yet we also know that some non-native speakers are not intelligible at all times because they acquired a language as an adult.

ASHA reviewed these considerations carefully when it updated its Accent Modification Practice Portal (ASHA, 2022), and this is a great place to refer anyone who wants a balanced view that addresses these ethical concerns. ASHA’s updated practice portal also makes the case that accent modification can be a valuable tool, and that SLPs are excellent providers of these services.  In the end, we need to respect any individual’s decision to make changes to their speech. In the words of a client: “as a non-native speaker I have the responsibility but also the right to look for those resources that will help me to improve my learning in English and feel more comfortable to express my ideas and get my point across in English and also to just to feel more confident and to embellish my self-esteem, and accent modification instructors for me are a guide and…I will recommend anyone who is experiencing the process of learning the English language to be aware of these services and to take advantage of them” (ASHA Voices, 2022).

15. Is accent training effective?

When I was in graduate school examining the evidence related to the acquisition of L2 phonology, the literature frequently referred to the dearth of research, but in the last few decades the landscape has changed. There is more and more evidence that positive outcomes can be achieved through accent training. Two important metastudies stand out, and both demonstrated positive effects. Saito reviewed 15 quasi-experimental intervention studies published since 1990 and found that “all intervention studies demonstrated significant improvement resulting from instruction except two studies” (Saito, 2012, p. 846). Lee, Jang, and Plonsky (2015) reviewed 86 studies and found a large effect for pronunciation instruction, stating that “the learners who received instructional treatments improved by 0.89 standard deviation units in comparison with their pretreatment performance; the between-group analyses demonstrated that learners in experimental groups outperformed those in control groups by 0.80 standard deviation units,” which according to the authors, represents medium to large effects (Lee, Jang, & Plonsky, 2015, pp. 356–357). A study conducted by Khurana and Huang (2013), which was not included in either of the metastudies, may have some added applicability to SLPs working in accent modification. A statistical analysis of the subjects’ pre- and posttraining self-evaluations showed higher ratings after accent modification, with the greatest impact coming in terms of increased confidence. This last point is particularly important for our services because clients determine whether accent modification works by choosing it and reporting positive outcomes. While objective measurements of increased intelligibility or naturalness are important, clients’ improved confidence in their own communication skills is another sign of success.

16. How does assessment work?

Before training begins, it’s important to understand the client’s goals, and a survey or questionnaire can be helpful ways to gain insight into their needs and priorities. The assessment itself should determine which segmental or suprasegmental features of a client’s speech have the greatest impact on their communication. Certainly, it’s important to prioritize intelligibility and to try to determine which phonemes or patterns play the largest role in reducing it. In addition, other factors such as naturalness can be evaluated subjectively to look for any features of the clients’ speech which may impact communication. SLPs will also need to review other factors such as differences in communication style. Some SLPs include language proficiency in terms of syntax and vocabulary, while others focus primarily on phonology. To analyze segmentals, it’s common to use target words or phrases to elicit the phonemes in several contexts while also considering phonotactics and allophones. Diagnostic passages are also helpful to sample connected speech and suprasegmentals. In addition, it’s important to get spontaneous speech samples through conversation or role plays.

17. What are some common targets?

At the segmental level, targets are highly dependent on the client’s L1 since phonemes which do not occur in their language are most likely to cause difficulty. Overall, the following consonant phonemes are very common: /θ,ð,w,v,z,ʒ,ɹ,ʤ,ʧ,ŋ/ while this set of allophones is also typical: /ɾ,ɾ̃,n̩,ʔ/. In addition, phonotactics will play a role, so a client who speaks Russian or German for example, may devoice obstruents in final position even when they have no problem voicing them initially or medially. Note that even though there is some overlap with sounds targeted when working with children with speech sound disorders, targets such as /s/ or /k/ are rare in accent modification. In addition, while most SLPs seldom work with vowels, in accent modification vowels share equal billing with consonants. The following are typical vowel phoneme targets: /ʌ,ə,ɝ,ɚ,æ,ɪ,ʊ,ɛ/, along with all r-colored vowels. In terms of allophones, vowel lengthening and nasality are also commonly addressed. At the suprasegmental level, stress (both lexical and phrasal), rate, prosody, linking, vowel reductions, and phrasing are commonly targeted. Prosody (also called intonation in our subfield) can be extremely important since it plays such an oversized role in successful communication.

18. What happens in a typical session?

In describing typical pronunciation work, Celce-Murcia and colleagues (2010) list the following as some of the typical training strategies:

•  Listen and imitate
•  Phonetic training
•  Minimal pairs
• Visual aids (cues to assist in the production of sound)
• Approximation drills
• Vowel production practice and stress pattern alteration
• Reading aloud
• Recordings of client’s production for auditory feedback and review

This list should in no way be considered exhaustive, and clinicians should use their imaginations and the ever-growing number of resources available to expand the range of strategies they use. Additional options include role-plays, dialogs, choral readings, shadowing, conversation starters, visual feedback, and auditory discrimination. Most sessions will have a productive balance of segmental and suprasegmental activities.

19. What are the rewards for clinicians and clients?

The two go together very well. When asked about the rewards of working in the field of accent modification, the answer from SLPs is almost universal—it is the clients. SLPs are exceptionally caring, and helping these clients achieve their communication goals is the most oft-cited benefit. Clients are also highly satisfied and report improvements in overall communication as well as confidence. Here are the words of some clients:

Client 1: Accent modification helped me realize that one’s accent doesn’t need to disappear in order to be understood; if you have an accent and have clear pronunciation you will be understood. And I believe that if you are dedicated and try hard you can definitely improve your pronunciation and become clearer to be understood by everyone. (McKinney, 209, p. 42)

Client 2: After 2 months of sessions, I started receiving feedback from customers on the clarity of my explanations during conference calls, and I could feel more confident picking up the phone and calling a customer instead of sending an email. I’ve witnessed progress already and I received all the tools I need to keep making progress for tomorrow. (McKinney, 209, p. 42)

20. Where can I learn more?

ASHA’s practice portal is a great place to start. There are also countless books written for the ESL market, as well as others, such as my own, that were written with SLPs in mind. Many SLPs also conduct online or in-person trainings, and this can be an excellent option to bridge gaps in knowledge. Social media sites are a great way to connect with others in this subfield, and the SLPs in Accent Modification Facebook group is by far the most popular. Professional organizations, such as the Corporate Speech Pathology Network (CORSPAN), have a high percentage of members working in accent modification, and ASHA and your state association may feature presentations on accent as well. Certainly, Speechpathology.com deserves a mention here for their selection of offerings on this topic. If you decide to try your hand at accent work, I hope this conversation has given you a big picture view and some ideas about how to begin. A love of languages, accents, and cultures brought me to this field, and if it brings you here as well, I am sure you will enjoy working with this amazing group of clients.

References

American Speech-Language-Hearing Association. (n.d.). Accent modification [Practice portal]. Retrieved 2022, from www.asha.org/Practice-Portal/Professional-Issues/Accent-Modification/

American Speech-Language-Hearing Association (2016). Code of ethics. Retrieved from https://www.asha.org/policy/

American Speech-Language-Hearing Association (2016). Scope of practice in speech language pathology. Retrieved from https://www.asha.org/policy/Crystal, D. (2008). A dictionary of linguistics and phonetics. Oxford, UK: Blackwell Publishing.

Abrahamsson, N., & Hyltenstam, K. (2009). Age of onset and nativelikeness in a second language: Listener perception versus linguistic scrutiny. Language Learning, 59(2), 249–306.

Asha voices: Different lenses on accent modification. @ASHA. (2021, November 11). Retrieved September 10, 2022, from https://leader.pubs.asha.org/do/10.1044/2021-1111-podcast-different-lens-accent-modification/full/

Celce-Murcia, M., Brinton, D., & Goodwin, J. M. (2010). Teaching pronunciation: A course book and reference guide. New York, NY: Cambridge University Press.

Crystal, D. (2008). A dictionary of linguistics and phonetics. Oxford, UK: Blackwell Publishing.

Fuertes, J. N., Gottdiener, D. H., Martin, H., Gilbert, T. C., & Giles, H. (2012). A metaanalysis of the effects of speakers’ accents on interpersonal evaluations. European Journal of Social Psychology 42, 120–133.

Hanzlíková, D., & Skarnitzl, R. (2017). Credibility of native and non-native speakers of English revisited: Do non-native listeners feel the same? Research in Language, 15, 285–298. 10.1515/rela-2017-0016.

Khurana, P., & Huang, E. (2013). Efficacy of accent modification training for international medical professionals. Journal of University Teaching & Learning Practice, 10(2), 1–11.

Lee, J., Jang J., & Plonsky, L. (2015). The effectiveness of second language pronunciation instruction: A meta-analysis. Applied Linguistics, 36(3), 345–366.

Lev-Ari, S., & Keysar, B. (2010). Why don’t we believe non-native speakers? The influence of accent on credibility. Journal of Experimental Social Psychology, 46(6), 1093–1096.

Levis, J. M., Sonsaat, S., Link, S., & Barriuso, T. A. (2016). Native and nonnative teachers of L2 pronunciation: Effects on learner performance. TESOL Quarterly, 50(4), 1–38.

McKinney R. (2019). Here's how to do accent modification: a manual for speech-language pathologists. Plural Publishing.

Munro, M. J. (2003). A primer on accent discrimination in the Canadian context. TESL Canada Journal, 20(2), 38–51.

Munro, M. J., & Derwing, T. M. (1995). Foreign accent, comprehensibility, and intelligibility in the speech of second language learners. Language Learning, 45, 73–97.

Saito, K. 2012. Effects of instruction on L2 pronunciation development: A synthesis of 15 quasi-experimental intervention studies. TESOL Quarterly, 46, 842–854.

Scovel, T. (1969). Foreign accents, language acquisition, and cerebral dominance. Language Learning, 19.