Article published in:
New Questions for the Next Decade
Edited by Gonia Jarema, Gary Libben and Victor Kuperman
[The Mental Lexicon 11:3] 2016
► pp. 375–400

Why we need to investigate casual speech to truly understand language production, processing and the mental lexicon

| University of Alberta
| Radboud University / Max Plank Institute for Psycholinguistics
The majority of studies addressing psycholinguistic questions focus on speech produced and processed in a careful, laboratory speech style. This ‘careful’ speech is very different from the speech that listeners encounter in casual conversations. This article argues that research on casual speech is necessary to show the validity of conclusions based on careful speech. Moreover, research on casual speech produces new insights and questions on the processes underlying communication and on the mental lexicon that cannot be revealed by research using careful speech. This article first places research on casual speech in its historic perspective. It then provides many examples of how casual speech differs from careful speech and shows that these differences may have important implications for psycholinguistic theories. Subsequently, the article discusses the challenges that research on casual speech faces, which stem from the high variability of this speech style, its necessary casual context, and that casual speech is connected speech. We also present opportunities for research on casual speech, mostly in the form of new experimental methods that facilitate research on connected speech. However, real progress can only be made if these new methods are combined with advanced (still to be developed) statistical techniques.
Keywords: casual speech, conversational speech, experimental paradigms, pronunciation variability, statistical analyses
Published online: 31 December 2016
https://doi.org/10.1075/ml.11.3.03tuc
References
Anderson, A.H., Bader, M., Bard, E.G., Boyle, E., Doherty, G., Garrod, S., & Sotillo, C
(1991) The HCRC map task corpus. Language and Speech, 34(4), 351–366. CrossrefGoogle Scholar
Baayen, R.H
(2008) Analyzing linguistic data. A practical introduction to statistics using r. Cambridge University Press. CrossrefGoogle Scholar
Baayen, R.H., van Rij, J., de Cat, C. & Wood, S.N
to appear). Autocorrelated errors in experimental data in the language sciences: Some solutions offered by Generalized Additive Mixed Models. In D. Speelman, K. Heylen, & D. Geeraerts (Eds.) Mixed effects regression models in linguistics Berlin: Springer Retrieved from http://​arxiv​.org​/abs​/1601​.02043 Crossref
Bates, D., Kliegl, R., Vasishth, S. & Baayen, R.H
submitted). Parsimonious mixed models.
Bates, E., & Liu, H
(1996) Cued shadowing. Language and Cognitive Processes, 11(6), 577–582. CrossrefGoogle Scholar
Bentum, M., Ernestus, M., ten Bosch, L. & van den Bosch, A
submitted). How do speech registers differ in the predictability of words?
Benzeghiba, M., De Mori, R., Deroo, O., Dupont, S., Erbes, T., Jouvet, D., Fissore, L., Laface, P., Mertins, A., Ris, S., Rose, R., Tyagi, V., & Wellekens, C
(2007) Automatic speech recognition and speech variability: A review. Speech Communication, 49(10), 763–786. CrossrefGoogle Scholar
Bernhard, D., & Tucker, B
(2015) The effects of duration on human processing of reduced speech. Canadian Acoustics, 43(3).Google Scholar
Biber, D
(1988) Variation across speech and writing. Cambridge: Cambridge University Press. CrossrefGoogle Scholar
Biber, D., Conrad, S., & Reppen, R
(1998) Corpus linguistics: Investigating language structure and use. Cambridge University Press. CrossrefGoogle Scholar
Brand, Sophie, & Ernestus, Mirjam
submitted). How do native listeners and learners of French comprehend French word pronunciation variants?
Brenner, D
(2013) The acoustics of Mandarin tones in careful and conversational speech. The Journal of the Acoustical Society of America, 134(5), 4246. CrossrefGoogle Scholar
Brenner, D.S
(2015) The phonetics of Mandarin tones in conversation. Retrieved from http://​arizona​.openrepository​.com​/arizona​/handle​/10150​/578721
Brouwer, S., Mitterer, H., & Huettig, F
(2012) Speech reductions change the dynamics of competition during spoken word recognition. Language and Cognitive Processes, 27(4), 539–571. CrossrefGoogle Scholar
Bürki, A., Ernestus, M., Gendrot, C., Fougeron, C., & Frauenfelder, U.H
(2011) What affects the presence versus absence of schwa and its duration: A corpus analysis of French connected speech. The Journal of the Acoustical Society of America, 130(6), 3980–3991. CrossrefGoogle Scholar
Bürki, A., Ernestus, M., & Frauenfelder, U.H
(2010) Is there only one “fenêtre” in the production lexicon? On-line evidence on the nature of phonological representations of pronunciation variants for French schwa words. Journal of Memory and Language, 621, 421–437. CrossrefGoogle Scholar
Çetin, Ö., & Shriberg, E
(2006) Speaker overlaps and ASR errors in meetings: Effects before, during, and after the overlap. In 2006 IEEE international conference on Acoustics Speech and Signal Processing Proceedings (vol. 11).
Chen, T.-Y., & Tucker, B.V
(2013) Sonorant onset pitch as a perceptual cue of lexical tones in Mandarin. Phonetica, 70(3), 207–239. CrossrefGoogle Scholar
Chomsky, N
(1965) Aspects of the theory of syntax. Cambridge, MA: MIT Press.Google Scholar
Connine, C.M., & Titone, D
(1996) Phoneme monitoring. Language and Cognitive Processes, 11(6), 635–646. CrossrefGoogle Scholar
De Chat, C
(2007) French dislocation. interpretation, syntax, acquisition [Oxford Studies in Theoretical Linguistics, 17] (pp. 288). Oxford: Oxford University Press.Google Scholar
Dilts, P.C
(2013) Modelling phonetic reduction in a corpus of spoken English using random forests and mixed-effects regression (Thesis). Retrieved from https://​era​.library​.ualberta​.ca​/downloads​/5425k999s
Drijvers, L., & Özyürek, A
in press). Visual context enhanced: The joint contribution of iconic gestures and visible speech to degraded speech comprehension. Journal of Speech, Language, and Hearing Research.
Engen, K.J.V., Baese-Berk, M., Baker, R.E., Choi, A., Kim, M., & Bradlow, A.R
(2010) The wildcat corpus of native-and foreign-accented English: Communicative efficiency across conversational dyads with varying language alignment profiles. Language and Speech, 53(4), 510–540. CrossrefGoogle Scholar
Ernestus, M
(2000) Voice assimilation and segment reduction in casual Dutch: A corpus-based study of the phonology-phonetic interface. Holland Institute of Generative Linguistics, Utrecht.Google Scholar
(2012) Message related variation: Segmental within speaker variation. In A.C. Cohn, C. Fougeron, & M. Huffman (Eds.), The Oxford handbook of laboratory phonology (pp. 92–102). Oxford: Oxford University Press.Google Scholar
Ernestus, M., & R.H. Baayen
(2011) Corpora and exemplars in phonology. In J. Goldsmith, J. Riggle, & A. Yu (Eds.), The handbook of phonological theory (2nd ed., pp. 374–400). Chichester, West Sussex: Wiley-Blackwell. CrossrefGoogle Scholar
Ernestus, M., Baayen, R.H., & Schreuder, R
(2002) The recognition of reduced word forms. Brain and Language, 811, 162–173. CrossrefGoogle Scholar
Ernestus, M., Hanique, I., & Verboom, E
(2015) The effect of speech situation on the occurrence of reduced word pronunciation variants. Journal of Phonetics, 481, 60–75. CrossrefGoogle Scholar
Ernestus, M., Lahey, M., Verhees, F., & Baayen, R.H
(2006) Lexical frequency and voice assimilation. Journal of the Acoustical Society of America, 1201, 1040–1051. CrossrefGoogle Scholar
Fowler, C.A., & Turvey, M.T
(1981) Immediate compensation in bite-block speech. Phonetica, 37(5–6), 306–326. CrossrefGoogle Scholar
Fu, Q., Zeng, F
(2000) Identification of temporal envelop cues in Chinese tone recognition. Asia Pacific Journal of Speech Language and Hearing, 51, 45–57. CrossrefGoogle Scholar
Gahl, S., Yao, Y., & Johnson, K
(2012) Why reduce? Phonological neighborhood density and phonetic reduction in spontaneous speech. Journal of Memory and Language, 66(4), 789–806. CrossrefGoogle Scholar
Galliano, S., Georois, E., Mostefa, D., Choukri, K., Bonastre, J.-F., & Gravier, J
(2005) ESTER phase II evaluation campaign for the rich transcription of French broadcast news. Proc. Interspeech 20051, 2453–2456.Google Scholar
Gaskell, G., & William, M.-W
(1998) Mechanisms of phonological inference in speech perception. Journal of Experimental Psychology: Human Perception and Performance, 241, 380–396. CrossrefGoogle Scholar
Gaygen, D.E., & Luce, P.A
(1998) Effects of modality on subjective frequency estimates and processing of spoken and printed words. Perception & Psychophysics, 60(3), 465–483. CrossrefGoogle Scholar
Gick, B
(2002) The use of ultrasound for linguistic phonetic fieldwork. Journal of the International Phonetic Association, 32(02), 113–121. CrossrefGoogle Scholar
Godfrey, J.J., Holliman, E.C., & McDaniel, J
(1992) Switchboard: Telephone speech corpus for research and development. In 1992 IEEE international conference on Acoustics, Speech, and Signal Processing, 1992. ICASSP-92 (vol. 11, pp. 517–520).   Crossref
Greenberg, S
(1999) Speaking in shorthand – A syllable-centric perspective for understanding pronunciation variation. Speech Communication, 291, 159–176. CrossrefGoogle Scholar
Goldinger, S.D., & Papesh, M.H
(2012) Pupil dilation reflects the creation and retrieval of memories. Current Directions in Psychological Science, 21(2), 90–95. CrossrefGoogle Scholar
Hastie, T.J., & Tibshirani, R.J
(2002) Generalized additive models (vol. 431). CRC Press 1990.Google Scholar
Heylighen, F., & Dewaele, J.-M
(2002) Variation in the contextuality of language: An empirical measure. Foundations of Science, 7(3), 293–340. CrossrefGoogle Scholar
Hockett, Charles F
1955 A manual of phonology. Baltimore: Waverly Press.Google Scholar
Hymes, D
(1992) The concept of communicative competence revisited. Thirty years of linguistic evolution. In Studies in honour of René Dirven on the occasion of his sixtieth birthday (pp. 31–57).Google Scholar
Kemps, R., Ernestus, M., Schreuder, R., & Baayen, R.H
(2004) Processing reduced word forms: The suffix restoration effect. Brain and Language, 191, 117–127. CrossrefGoogle Scholar
Klingner, J., Tversky, B., & Hanrahan, P
(2011) Effects of visual and verbal presentation on cognitive load in vigilance, memory, and arithmetic tasks. Psychophysiology, 48(3), 323–332. CrossrefGoogle Scholar
Koch, X., & Janse, E
(2016) Speech rate effects on the processing of conversational speech across the adult life span. The Journal of the Acoustical Society of America, 139(4), 1618–1636. CrossrefGoogle Scholar
Kruschke, J.K
(2010) What to believe: Bayesian methods for data analysis. Trends in Cognitive Sciences, 14(7), 293–300. CrossrefGoogle Scholar
(2014) Doing Bayesian data analysis: A tutorial with R, JAGS, and Stan. Academic Press.Google Scholar
Kryuchkova, T., Tucker, B.V., Wurm, L.H., & Baayen, R.H
(2012) Danger and usefulness are detected early in auditory lexical processing: Evidence from electroencephalography. Brain and Language, 122(2), 81–91. CrossrefGoogle Scholar
Labov, W
(1972) Sociolinguistic patterns. University of Pennsylvania Press.Google Scholar
Lahiri, A., & Reetz, H
(2002) ‘Underspecified recognition’. In Carlos Gussenhoven, Natasha Warner, & Toni Rietveld (Eds.), Phonology & phonetics: Laboratory phonology VII (pp. 637–676). Berlin, Mouton. CrossrefGoogle Scholar
Levelt, W.J.M., Roelofs, A., & Meyer, A.S
(1999) A theory of lexical access in speech production. Behavioral and Brain Sciences, 221, 1–38. CrossrefGoogle Scholar
Lindblom, B
(1963) Spectrographic study of vowel reduction. The Journal of the Acoustical Society of America, 35(11), 1773–1781. CrossrefGoogle Scholar
Liu, S., & Samuel, A.G
(2004) Perception of Mandarin lexical tones when F0 information is neutralized. Language & Speech, 471, 109–138. CrossrefGoogle Scholar
MacWhinney, B
(2000) The childes project: Tools for analyzing talk (3rd ed.). Mahwah, NJ: Lawrence Erlbaum Associates.Google Scholar
McLennan, C.T., Luce, P.A., & Charles-Luce, J
(2003) Representation of lexical form. Journal of Experimental Psychology: Learning, Memory, and Cognition, 29(4), 539–553. CrossrefGoogle Scholar
McQueen, J
(1996) Word spotting. Language and Cognitive Processes, 11(6), 695–699. CrossrefGoogle Scholar
Mehta, G., & Cutler, A
(1988) Detection of target phonemes in spontaneous and read speech. Language and Speech, 31(Pt 2), 135–156. CrossrefGoogle Scholar
Mirman, D. , Dixon, J.A., & Magnuson, J.S
(2008) Statistical and computational models of the visual world paradigm: Growth curves and individual differences. Journal of Memory and Language, 59(4), 475–494. CrossrefGoogle Scholar
Mulder, K., ten Bosch, L., & Boves, L
submitted). Comparing different methods for analyzing ERP signals.
Munson, B., & Solomon, N.P
(2004) The effect of phonological neighborhood density on vowel articulation. Journal of Speech, Language, and Hearing Research, 47(5), 1048–1058. CrossrefGoogle Scholar
Oleson, J.J., Cavanaugh, J.E., McMurray, B., & Brown, G
(2015) Detecting time-specific differences between temporal nonlinear curves: Analyzing data from the visual world paradigm. Statistical Methods in Medical Research, 0962280215607411.Google Scholar
Oostdijk, N
(2000) The spoken Dutch Corpus Project. The ELRA Newsletter, 51, 4–8.Google Scholar
Pitt, M.A., Dilley, L., Johnson, K., Kiesling, S., Raymond, W., Hume, E., & Fosler-Lussier, E
(2007) Buckeye corpus of conversational speech (2nd release) [www​.buckeyecorpus​.osu​.edu] Columbus, OH: Department of Psychology. Ohio State University (Distributor).Google Scholar
Pluymaekers, M., Ernestus, M., & Baayen, R
(2006) Articulatory planning is continuous and sensitive to informational redundancy. Phonetica, 62(2–4), 146–159. CrossrefGoogle Scholar
Podlubny, R., Geeraert, K., Tucker, B.V
(2015) It’s all about, like, acoustics. Proceedings of the 18th international Congress of Phonetic Sciences . Glasgow, UK: The University of Glasgow. Paper number 0477.
Podlubny, R., Tucker, B.V., & Nearey, T
(2011) ‘Sorry, what was that?’: The roles of pitch, duration, and amplitude in the perception of reduced speech. Poster presented at the Nijmegen Spontaneous Speech Workshop , Nijmegen, NL.
Pollack, I., & Pickett, J.M
(1963) Intelligibility of excerpts from conversational speech. Language and Speech, 61, 165–171. CrossrefGoogle Scholar
Ranbom, L.J., & Connine, C.M
(2007) Lexical representation of phonological variation in spoken word recognition. Journal of Memory and Language, 57(2), 273–298. CrossrefGoogle Scholar
Richter, E
1930 Beobachtungen über Anglitt und Abglitt an Sprachkurven und umgekehrt laufenden Phonogrammplatten. In Paul Menzerath (Ed.), Berichte über die I. Tagung der Internationalen Gesellschaft für experimentelle Phonetik (pp. 87–90). Bonn: Scheur.Google Scholar
Ruiter, de, L.E
(2015) Information status marking in spontaneous vs. read speech in story-telling tasks – Evidence from intonation analysis using GToBI. Journal of Phonetics, 481, 29–44. CrossrefGoogle Scholar
Schönle, P.W., Gräbe, K., Wenig, P., Höhne, J., Schrader, J., & Conrad, B
(1987) Electromagnetic articulography: Use of alternating magnetic fields for tracking movements of multiple points inside and outside the vocal tract. Brain and Language, 31(1), 26–35. CrossrefGoogle Scholar
Schweitzer, K., Walsh, M., Calhoun, S., Schütze, H., Möbius, B., Schweitzer, A., & Dogil, G
(2015) Exploring the relationship between intonation and the lexicon: Evidence for lexicalised storage of intonation. Speech Communication, 661, 65–81. CrossrefGoogle Scholar
Stampe, D
(1973) A dissertation on natural phonology. PhD Diss. University of Chicago.Google Scholar
Stone, M
(1990) A three‐dimensional model of tongue movement based on ultrasound and X‐ray microbeam data. The Journal of the Acoustical Society of America, 87(5), 2207–2217. CrossrefGoogle Scholar
Taft, M., & Chen, H.C
(1992) Judging homophony in Chinese: The influence of tones. Advances in Psychology, 901, 151–172. CrossrefGoogle Scholar
Tagliamonte, S.A., & Baayen, R.H
(2012) Models, forests, and trees of York English: Was/were variation as a case study for statistical practice. Language Variation and Change, 24(2), 135–178. CrossrefGoogle Scholar
Torreira, F., Adda-Decker, M., & Ernestus, M
(2010) The nijmegen corpus of casual French. Speech Communication, 521, 201–221. CrossrefGoogle Scholar
Tucker, B.V
(2007) Spoken word recognition of the reduced American English Flap. The University of Arizona. Retrieved from http://​hdl​.handle​.net​/10150​/194987Google Scholar
(2011) The effect of reduction on the processing of flaps and /g/ in isolated words. Journal of Phonetics, 39(3), 312–318. CrossrefGoogle Scholar
Tyrone, M.E., & Mauk, C.E
(2010) Sign lowering and phonetic reduction in American Sign Language. Journal of Phonetics, 38(2), 317–328. CrossrefGoogle Scholar
van Rij, J., Natalya, P., van Rijn, H., Wood, S.N., & Baayen, R.H
submitted). Pupil dilation to study cognitive processing: Challenges and solutions for time course analyses.
Van de Ven, M., Ernestus, M., & Schreuder, R
(2012) Predicting acoustically reduced words in spontaneous speech: The role of semantic/syntactic and acoustic cues in context. Laboratory Phonology, 31, 455–481. CrossrefGoogle Scholar
Viebahn, M., Ernestus, M., & McQueen, J
(2015) Syntactic predictability in the recognition of carefully and casually produced speech. Journal of Experimental Psychology: Learning, Memory, and Cognition, 41(6), 1684–1702. CrossrefGoogle Scholar
Wagner, P., Trouvain, J., & Zimmerer, F
(2015) In defense of stylistic diversity in speech research. Journal of Phonetics, 481, 1–12. CrossrefGoogle Scholar
Warner, N
(2011) Reduction. In M. van Oostendorp, C. Ewen, E. Hume, & K. Rice (Eds.), The Blackwell Companion to Phonology: General issues and segmental phonology (vol. 11, pp. 1866–1891). John Wiley & Sons. CrossrefGoogle Scholar
(2012) Methods for studying spontaneous speech. In A. Cohn, C. Fougeron, & M. Huffman (Eds.), The Oxford handbook of laboratory phonology (pp. 621–633). Oxford: Oxford University Press.Google Scholar
Warner, N., & Tucker, B.V
(2011) Phonetic variability of stops and flaps in spontaneous and careful speech. The Journal of the Acoustical Society of America, 130(3), 1606–1617. CrossrefGoogle Scholar
Wiggers, P., & Rothkrantz, L.J.M
(2007) Exploratory analysis of word use and sentence length in the spoken Dutch Corpus. In V. Matoušek & P. Mautner (Eds.), Text, speech and dialogue (pp. 366–373). Springer Berlin Heidelberg. CrossrefGoogle Scholar
Willems, R.M., Frank, S.L., Nijhof, A.D., Hagoort, P., & Bosch, A. van den
(2016) Prediction during natural language comprehension. Cerebral Cortex, 26(6), 2506–2516. CrossrefGoogle Scholar
Wood, S.N
(2006) Generalized additive models. New York: Chapman & Hall/CRC. CrossrefGoogle Scholar
Wrench, A.A., & Scobbie, J.M
(2011) Very high frame rate ultrasound tongue imaging. In Proceedings of the 9th International Seminar On Speech Production (ISSP) (pp. 155–162).
Wurm, L.H., & Fisicaro, S.A
(2014) What residualizing predictors in regression analyses does (and what it does not do). Journal of Memory and Language, 721, 37–48. CrossrefGoogle Scholar
Xiong, W., Droppo, J., Huang, X., Seide, F., Seltzer, M., Stolcke, A., & Zweig, G
(2016) The Microsoft 2016 Conversational Speech Recognition System. arXiv:1609.03528 [Cs]. Retrieved from http://​arxiv​.org​/abs​/1609​.03528
Xu, Y
(2010) In defense of lab speech. Journal of Phonetics, 38(3), 329–336. CrossrefGoogle Scholar
Zekveld, A.A., Kramer, S.E., & Festen, J.M
(2010) Pupil response as an indication of effortful listening: The influence of sentence intelligibility. Ear and Hearing, 311, 480–490. CrossrefGoogle Scholar
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