Teaching & Learning Guide for: The Study of Variation from Two Perspectives
Authors: Gentry Brunner Elizabeth 
Published: September 2009

Author’s Introduction

The study of language variation is fundamental to both sociolinguistics and forensic linguistics (FL). By understanding the similarities between the two fields, sociolinguists can begin to contribute to forensic issues, such as speaker identification. In forensic speaker identification, the linguist determines whether an unknown voice belongs to a known speaker. An example of this would be determining the likelihood that a recorded extortion threat was made by a particular suspect. FL is an applied field which is not only valuable to academia but to society as well. In the United States, many FL tasks are performed by nonlinguists; however, a few sociolinguists have stepped up to the challenge. Sociolinguists are especially well equipped for forensic casework, as they are already familiar with working with real speech and its inherent variation. In this guide, forensic speaker identification is approached by analyzing five types of variation, which sociolinguists are amply familiar with: variation across groups of speakers, variation within speakers, variation between speakers, variation over time, and variation in perception.

Author Recommends

Forensic Linguistics

Rose, Philip. 2002. Forensic speaker identification. New York: Taylor & Francis.

A must for anyone interested in forensic phonetics. This is a thorough introduction to forensic phonetics that promotes a Bayesian (likelihood ratio or LR) framework for interpreting the importance of various linguistic parameters. Detailed coverage is given to all aspects of forensic speaker identification, with helpful comments on the forensic significance of several phonetic issues.

Hollien, Harry. 2002. Forensic voice identification. London: Academic Press.

Another comprehensive book about forensic phonetics. This is a great reference and introduction. The writing style is informal and enjoyable, and the book is peppered with interesting short stories about previous cases.

International Journal of Speech, Language, and the Law (formerly Forensic Linguistics).

The go‐to journal for FL. This is certainly not limited to forensic phoneticians; originally entitled Forensic Linguistics, the journal changed its name in 2003 to reflect a broader scope of language and law issues. Membership in IAFPA and/or IAFL (see Internet Resources that follow) includes subscription to this.

Coulthard, Malcolm and Alison Johnson. 2008. An introduction to forensic linguistics. New York: Routledge.

This is a good introduction to the many varied topics that fall within the domain of FL, such as text analysis and legal language. It is great for a class on FL in general that will not be focusing on forensic phonetics.

Shuy, Roger W. 2006. Linguistics in the courtroom: a practical guide. New York: Oxford University Press.

Once the linguist begins to get involved with forensic cases, this handbook will explain how to go about the actual casework. It gives practical advice for every step of the case, from starting out to dealing with attorneys to courtroom testimony.

Sociolinguistics

Milroy, Lesley and Matthew Gordon. 2003. Sociolinguistics: method and interpretation. Malden, MA: Blackwell.

This is what every sociolinguist should read before launching a research project. It explains the history and theory behind every aspect of sociolinguistic methodology.

Bayley, Robert and Ceil Lucas. 2007. Sociolinguistic variation: theories, methods, and applications. Cambridge, UK: Cambridge University Press.

An up‐to‐date overview of the field of sociolinguistics. Each chapter is a different topic written by a leading expert. Sections include theories, methods, and applications.

Chambers, J. K., Peter Trudgill, and Natalie Schilling‐Estes. 2002. The handbook of language variation and change. Malden, MA: Blackwell.

Another great resource that covers the spectrum of language variation research. The chapters are again written by sociolinguistic leaders. Sections include methodologies, linguistic structure, social factors, contact, and language and societies.

Wolfram, Walt and Natalie Schilling‐Estes. 2002. American English: dialects and variation. Malden, MA: Blackwell.

Good introduction to dialects and language variation in the United States.

Internet Resources

International Association of Forensic Phonetics and Acoustics (IAFPA):

<http://www.iafpa.net>

Website for the International Association of Forensic Phonetics and Acoustics. Includes a code of practice and resolutions, as well as association and conference information.

International Association of Forensic Linguists (IAFL):

<http://www.iafl.org>

Website for the International Association of Forensic Linguists. Includes an expansive bibliography (through 2002) in addition to association and conference information.

Forensic‐Linguistics List:

<https://www.jiscmail.ac.uk/cgi‐bin/webadmin?A0=forensic‐linguistics>

A fairly active e‐mail listserv dealing with various FL themes.

Dynamic Variability in Speech (DyViS):

<http://www.ling.cam.ac.uk/dyvis/>

Website for the Dynamic Variability in Speech project. The authors of a large forensic phonetic study of British English provide a detailed overview of their project, along with downloadable reports of their results.

Thomas, Erik R. and Tyler Kendall. 2007. NORM: The vowel normalization and plotting suite:

<http://ncslaap.lib.ncsu.edu/tools/norm/>

A fantastic free resource that allows you to normalize and plot vowels. Includes explanations of multiple normalization techniques so you can use one that is appropriate for your data. It is simple to use, explained clearly, and cranks out color plots that look great.

Sample Course Outline

Forensic phonetics is the primary focus of this course. It approaches this from a variationist perspective, targeting students with an interest in and knowledge of sociolinguistics. The class is for advanced undergraduate and graduate students (knowledge of statistics is beneficial, although not required). The recommended text is Forensic Speaker Identification (2002) by Philip Rose.

Syllabus

Week 1: What is variation? Why and how do we study variation?

This is a general review of variation and sociolinguistics, followed by a brief introduction to FL. Different types of variations are presented.

Suggested reading:

Milroy, Lesley and Matthew Gordon. 2003. Sociolinguistics: method and interpretation, chapter 1. Malden, MA: Blackwell. 1–22.

Brunner, Elizabeth. 2009. The study of variation from two perspectives. Language and Linguistics Compass 3(3).734–750.

Rose, chapter 1, 1–8.

Week 2: Class corpus collection and creation

Students learn about the corpus they will create as a class and begin recruiting participants. This should be completed by Week 5.

Suggested reading:

Nolan, Francis, Kirsty McDougall, Gea de Jong, and Toby Hudson. 2006. A forensic phonetic study of ‘dynamic’ sources of variability in speech: The DyViS project. Proceedings of the 11th Australasian International Conference on Speech Science and Technology, ed. by Paul Warren and Catherine I. Watson, 13–18, Auckland, New Zealand, 6–8 December.

Byrne, Catherine and Paul Foulkes. 2004. The ‘mobile phone effect’ on vowel formants. International Journal of Speech, Language, and the Law 11(1).83–102.

Week 3: Why and how do we study FL?

The class starts to delve deeper into the field of FL, discussing the ethical and practical questions associated with it.

Suggested reading:

Rose, chapter 2, 9–31.

Braun, Angelika and Hermann J. Künzel. 1998. Is forensic speaker identification unethical – or can it be unethical not to do it? Forensic Linguistics 5(1).10–21.

Week 4: How do we study FL (continued)

This week focuses on the different types of forensic speaker identification. It also includes how not to do FL, discussing the denounced concept of voiceprints.

Suggested reading:

Rose, chapter 5, 81–123.

Week 5: Research Methods in FL

The technical details of FL analysis are introduced, including the parameters (features) which are used. The LR is introduced, and Learning Exercise #1 is used to demonstrate this (see next section).

Suggested reading:

Rose, chapter 3, 33–53 and chapter 4, 55–79.

Week 6: Variation across groups of speakers

This begins the in‐depth coverage of the five types of variations introduced during the first week. Dialectal variation is discussed, both in itself and from a forensic standpoint.

Suggested reading:

Dumas, Bethany K. 1990. Voice identification in a criminal law context. American Speech 65(4).341–348.

Shuy, Roger W. 1990. Dialect as evidence in law cases. Journal of English Linguistics 23.195–208.

Labov, William, Sharon Ash, and Charles Boberg. 2006. The Atlas of North American English, chapter 11. New York: Walter de Gruyter. 119–151.

Week 7: Variation across groups of speakers (continued)

This continues the focus on variation across dialect groups. It also stresses the need for knowledge of the distribution of linguistic features throughout the population. Learning Exercise #2 gives students experience with dialectal variation.

Suggested reading:

Labov, William and Wendell A. Harris. 1994. Addressing social issues through linguistic evidence. Language and the law, ed. by John Gibbons, 265–305. New York: Longman.

Hudson, Toby, Gea de Jong, Kirsty McDougall, Philip Harrison, and Francis Nolan. 2007. F0 statistics for 100 young male speakers of Standard Southern British English. Proceedings of the 16th International Congress of Phonetic Sciences, Saarbrucken, ed. by Jürgen Trouvain and William J. Barry, 1809–12. Germany, 6–10 August.

Week 8: Variation within speakers

The next type of variation centers on style‐shifting and the resulting differences within speakers.

Suggested reading:

Schilling‐Estes, Natalie. 2002. Investigating stylistic variation. The handbook of language variation and change, ed. by J.K. Chambers, Peter Trudgill, and Natalie Schilling‐Estes, 375–401. Malden, MA: Blackwell.

Bahr, Ruth Huntley, and Kimberley J. Pass. 1996. The influence of style‐shifting on voice identification. Forensic Linguistics 3(1).24–38.

Week 9: Variation within speakers (continued)

This continues looking at intra‐speaker variation, particularly intentional changes such as disguise. Learning Exercise #3 is used.

Suggested reading:

Blatchford, Helen and Paul Foulkes. 2006. Identification of voices in shouting. International Journal of Speech, Language, and the Law 13(2).241–254.

Masthoff, Herbert. 1996. A report on a voice disguise experiment. Forensic Linguistics 3(1).160–167.

Week 10: Variation between speakers

The concept of an idiolect is introduced and the investigation of individuals is discussed.

Suggested reading:

Hazen, Kirk. 2006. Idiolect. The encyclopaedia of language and linguistics, 2nd edn., Vol. 5, ed. by Keith Brown, 512–514. Oxford, UK: Elsevier.

Schreier, Daniel. 2006. The backyard as a dialect boundary: individuation, linguistic heterogeneity, and sociolinguistic eccentricity in a small speech community. Journal of English Linguistics 34(1).26–57.

Week 11: Variation between speakers (continued)

Researching individual differences using siblings is presented. Learning Exercise #4 is used.

Suggested reading:

Loakes, Deborah. 2003. A forensic phonetic analysis of the speech patterns of non‐identical twins. Melbourne Papers in Linguistics and Applied Linguistics 3(1).57–75.

Week 12: Variation over time

The concepts and problems of real and apparent time are discussed and related to the issue of noncontemporary speech samples in FL.

Suggested reading:

Bailey, Guy. 2002. Real and apparent time. The handbook of language variation and change, ed. by J.K. Chambers, Peter Trudgill, and Natalie Schilling‐Estes, 312–332. Malden, MA: Blackwell.

Hollien, Harry and Reva Schwartz. 2000. Aural‐perceptual speaker identification: problems with noncontemporary samples. Forensic Linguistics 7(2).199–211.

Week 13: Variation in perception

The importance of perception is addressed, particularly focusing on those factors that can influence the perception of earwitnesses. Learning Exercise #5 demonstrates how to conduct a voice line‐up.

Suggested reading:

Thomas, Erik R. 2002. Sociophonetic applications of speech perception experiments. American Speech 77(2).115–147.

Yarmey, A. Daniel. 2004. Common‐sense beliefs, recognition and the identification of familiar and unfamiliar speakers from verbal and non‐linguistic vocalizations. International Journal of Speech, Language, and the Law 11(2).267–277.

Week 14: Summing it all up

Forensic speaker identification is reviewed. Ends with an overview of drawing conclusions about a speaker based on their voice (the areas of linguistic asylum and linguistic profiling) and a class debate about these issues.

Suggested reading:

Rose, chapter 12, 327–335.

Eades, Diana and Jacques Arends. 2004. Using language in the determination of national origin of asylum seekers: an introduction. International Journal of Speech, Language, and the Law 11(2).179–199.

Baugh, John. 2007. Attitudes toward variation and ear‐witness testimony. Sociolinguistic variation: theories, methods, and applications, ed. by Robert Bayley and Ceil Lucas, 338–348. Cambridge, UK: Cambridge University Press.

Week 15: Project presentations

Students present the results of their projects.

Learning Exercises

Learning Exercise #1: LR demonstration

The purpose of this exercise is to demonstrate the Likelihood Ratio (LR) and how it works. The point of this exercise is NOT to labor over a calculator. (Remember, this is not a math class. We do not want students to get bogged down in statistical details and give up!) So stick to the basics of what the LR is comparing. Walk students through the examples given in Rose, chapter 11. (As you are presenting it, they do not need to read it.) Make sure to show this visually, for example, by including spectrograms and tables (like Rose’s Tables 11.2 and 11.3). Ask students about the different cells within the tables to ensure they understand them. They do not necessarily need to do the math themselves, but they need to be able to verbally express what the various LRs mean.

Learning Exercise #2: Detecting dialect differences

The purpose of this exercise is to help students realize the difficulties of discriminating between similar dialects, especially if they are unfamiliar with them. Play recordings of multiple speakers to students. (You may obtain speech samples from a variety of electronic corpora, depending on your institution’s access, or from your own research.) Ask the students how many different dialects are represented. Ask students which speakers belong to the same dialects. Which features/parameters are they using to make these distinctions? Discuss the role of familiarity. For example, can students in South Dakota tell the difference between NYC and Boston dialects? Can students in Ohio tell the difference between Texas and Georgia dialects? Contrast this to dialects that students are likely to be very familiar with.

Learning Exercise #3: Single speaker style‐shifting

The goal of this exercise is to highlight the differences within a single person’s speech. Record someone (perhaps yourself or a helpful acquaintance) in a variety of speaking situations. These may include, for example, speaking in their work setting, speaking with their spouse, with their children, on the phone with older relatives, to a store clerk, when they have a cold, etc. In addition to this, record them deliberately disguising their voice in a variety of ways. Play (short clips of) these recordings to students and ask them to identify five features/parameters that remain the same across most or all of the speaking situations and five features that vary among most or all of the speaking situations. This will be fairly difficult to do auditorily, with many recordings, but it should get the point across. You may also do some acoustic analyses ahead of time so you can show them additional similarities and differences.

Learning Exercise #4: Sibling similarities and differences

The purpose of this exercise is to demonstrate the difficulty of differentiating the speech of two speakers with similar voices. Record two siblings of the same gender (ideally twins). Play several short clips of the recordings and ask students to determine if the voices they hear are from the same or different speakers (mix up the answers, of course). Discuss whether and why this is an easy or difficult task. Play the two speakers again and ask the students to identify three features they share and three features that differentiate them. (If this task is too easy, you might want to use speakers whose voices are more similar.) In addition to the auditory features identified, discuss and show acoustic features that you discerned beforehand.

Learning Exercise #5: Earwitness experience

The point of this exercise is for students to participate in a voice line‐up. Enlist an acquaintance with whom your students are unfamiliar. Have this person stick their head into the room and interrupt at the beginning of the class. Continue with the lesson. Towards the end of the period, inform students that they are now going to participate in a voice line‐up as earwitnesses of the earlier speaker. Present the line‐up you have already created (see Forensic Linguistics, volume 3, issue 1, 1996, for instructions), requiring students to follow recommended line‐up procedures.

Reveal the correct answer. (For a twist, you could have a target‐absent line‐up so that the correct answer is none of the voices heard.) Discuss the students’ accuracy and the task itself.

Final Project

At the beginning of the course, create a class corpus that can be used for the project. Students are responsible for finding 2–3 participants each. This may be a very involved corpus (such as the one based on the DyViS project, Nolan et al. 2006), but the type and quality of data is at the professor’s discretion. Regardless of the corpus’ structure, ensure that each participant is recorded using a variety of styles. Also, make sure the participants are all similar (matched for gender, age, socioeconomic status, dialect, etc.), ideally including some siblings. The students will then use this corpus as their data for the project. There are five topics to choose from (shown next), based on the types of variation presented in class. Students will present brief presentations on their project during the last week of the course.

Similarities across multiple speakers in the corpus: begin to gather population data for this corpus.

Stylistic variation: choose 1–3 speakers in this corpus and analyze the similarities and differences within each speaker’s different styles.

Sibling variation: analyze the similarities and differences between 2–3 speakers who sound similar (ideally siblings/twins).

Differences over time: interview one of the original participants 2 months later and determine what, if any, differences exist in their non‐contemporary speech samples.

Voice line‐up: create an earwitness study and conduct it with 4–6 people who are not familiar with the speakers.

Focus Questions

What is variation? How is it the focus of both sociolinguistic and FL research?

What are the strengths and weaknesses of auditory and acoustic approaches? What are typical parameters/features that are studied with each approach?

What is an LR? How does it apply to linguistic variation?

Why are large‐scale population studies important to FL?

How can dialectal studies be important in some FL casework?

Why is knowledge about style important to FL?

Explain the concept of an idiolect. What are some ways of distinguishing individual voices?

Explain the idea of real and apparent time. How is this relevant to FL?

What is a voice (earwitness) line‐up? What are some limitations of the speakers’ perceptions?