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Among the more than 150 interesting symposia at AAAS 2011, Section Z (Linguistics) sponsored five. I posted earlier about the symposium on "What Bilinguals Tell Us About Mind and Brain". I'm adding a link today to another one, "From Freud to fMRI: Untangling the Mystery of Stuttering". Its abstract:

This symposium will track current developments in the study of stuttering, the fruit of recent collaborations among researchers in the fields of genetics, speech motor control, and language processing. Until the past decade, much of the research into this common yet poorly understood communication disorder tended to be narrowly focused on accounts within a single discipline, from psychoanalysis to learning theory to articulatory control to hemispheric asymmetry. In this symposium, we will provide examples of the cross-disciplinary research that is changing consensus on the probable basis for stuttering. Recent advances in genetics, brain imaging, and speech motor control will be discussed in terms of their ramifications for better understanding this elusive disorder as well as treating it more effectively.

And I'll assert again that the AAAS would do itself and (more important) its mission a service by putting slides and videos or audios of these symposia on the web, for free public access. I was happy to learn from Stephen Anderson that steps of this kind are now under consideration.

The contributions to this symposium, with their abstracts, are listed below.

Dennis Drayna, National Institutes on Deafness and Other Communication Disorders, "Identifying the Genetic Contributions to Stuttering":

The first speaker will summarize how studies on genetic factors in stuttering have led to the first understanding of the causes of the disorder at the molecular level. This portion of the symposium will also discuss how additional chromosomal loci may identify additional molecular deficits that cause stuttering, and also relate stuttering to other human communication disorders.

Luc de Nil, University of Toronto, "Brain Anatomy and Function in People Who Stutter":

This portion of the session will integrate recent findings in the neuroimaging literature. In particular, the speaker will discuss how a substantial number of findings differentiate children and adults who stutter from typically fluent speakers with respect to brain morphology as well as functional speech/language and motor processes. These findings help to elucidate the possible deficits that contribute to the development and persistence of stuttering. Importantly, it is also evident that many of these patterns are responsive to therapeutic intervention, suggesting that some aspects of these neurological profiles are plastic and amenable to behavioral treatment.

Anne Smith, Purdue University, "How Stuttering Emerges from the Interfaces Between Linguistic and Motor Processing":

The third speaker will demonstrate how diverse findings of speech-motor learning and control deficits in people who stutter can be integrated with a companion literature that proposes a more central deficit in speech-language processing. She will present recent findings showing that language planning in people who stutter uniquely destabilizes speech motor control, a finding made possible by viewing stuttering through an interdisciplinary lens. She will conclude with discussion of how our understanding of the nature and most efficient treatment of stuttering can be further advanced through integration of additional disciplinary approaches.

Under the current arrangements, that's all the information that the AAAS offers about the session. (Well, you could write off for an audio CD of the presentations; but I doubt that many people will do so, or for that matter that they'll be able to get much value from the audio without the slides.)

However, as usual, you could use Google Scholar to find recent publications by Dennis Drayna, Luc de Nil, and Anne Smith on this topic. You would turn up, for example, Lindsey Olander, Anne Smith, and Howard N. Zelaznik, "Evidence That a Motor Timing Deficit Is a Factor in the Development of Stuttering", Journal of Speech, Language, and Hearing Research, 53:876-886 August 2010. The abstract:

Purpose: To determine whether young children who stutter have a basic motor timing and/or a coordination deficit.

Method: Between-hands coordination and variability of rhythmic motor timing were assessed in 17 children who stutter (4–6 years of age) and 13 age-matched controls. Children clapped in rhythm with a metronome with a 600-ms interbeat interval and then attempted to continue to match this target rate for 32 unpaced claps.

Results: Children who stutter did not significantly differ from children who were typically developing on mean clapping rate or number of usable trials produced; however, they produced remarkably higher variability levels of interclap interval. Of particular interest was the bimodal distribution of the stuttering children on clapping variability. One subgroup of children who stutter clustered within the normal range, but 60% of the children who stutter exhibited timing variability that was greater than the poorest performing nonstuttering child. Children who stutter were not more variable in measures of coordination between the 2 hands (mean and median phase difference between hands).

Conclusion: We infer that there is a subgroup of young stuttering children who exhibit a nonspeech motor timing deficit, and we discuss this result as it pertains to recovery or persistence of stuttering.

Here's a figure that illustrates the lack of difference in mean clapping rate:

And here's an illustration of the differences in clapping variability:

The authors observe that

These results provide clear evidence that in its early years, developmental stuttering is associated with a fundamental deficit in the child's ability to generate consistent, rhythmic motor behaviors. This suggests that children who stutter have atypical development of neural networks in the brain involved in the control of speech and other complex movements.

The reference to "developmental stuttering" raises an intriguing possibility, which they discuss as follows:

An intriguing speculation arising from the present work is that the presence of a general motor timing deficit in children who stutter may be an early indicator of persistent stuttering. In other words, children who stutter who do not show evidence of a general timing deficit might spontaneously recover, whereas those who do show abnormally high motor timing variability will persist. Currently there is no way to determine whether a child who stutters will continue to do so into adulthood. Findings of the Illinois Stuttering Project (Ambrose & Yairi, 1999; Paden, Yairi, & Ambrose, 1999; Watkins, Yairi, & Ambrose, 1999; Yairi & Ambrose, 1999)—a 4-year longitudinal study of children who stuttered—revealed a 75% spontaneous recovery rate for 3-year-olds who stuttered. Because the children in the current study were 4-, 5-, and 6-year-olds, and as a result had already been stuttering for 1–3 years, recovery rates for this group should be approximately 50%. The distribution of clapping variability levels produced by children who stutter in the present study (41% of the children who stuttered falling within the range produced by typically developing children, and 59% producing higher variability levels than children who stuttered) roughly matches expected recovery rates.

Although it is beyond the scope of the present study to strongly suggest that clapping variability is an early marker of stuttering persistence versus recovery, the bimodal-looking distribution in the coefficient of variation in the children who stuttered provides a promising possibility for the early identification of persistent stuttering and will continue to be investigated in future work in our laboratory. A procedure for the early detection of persistent stuttering would clearly be beneficial for speech language pathologists and families of children who stutter when deciding whether a young child who is stuttering should enter therapy.

I've long wondered whether machine-learning methods applied to detailed speech-timing measures might be able to predict which cases of developmental stuttering would "grow out of it" and which would not. But if something as simply as clapping variability could accomplish such a prediction, that would be wonderful. And perhaps the results of a set of simple quantitative measures, of which this might be one, would do even better.

This is a significant problem, worth some focused effort to solve, since the incidence of developmental stuttering is apparently in the range of 5-10%. The problem disappears without intervention in most of the children who are affected; and (in addition to possible waste of time and money) there is some concern that early intervention might make the problem worse in some cases, by making sufferers anxious about the problem. On the other hand, persistent stuttering can be improved by therapy, and apparently in this case earlier intervention is better.

For some indication of the state of controversy in this field, see Peter Howell, "Listen to the Lessons of The King's Speech", Nature 470 2/2/2011; and a response by Mark Onslow and Ann Packman, "Stuttering studies support treatment", Nature 470 2/24/2011.


  1. Mr Punch said,

    March 9, 2011 @ 10:02 am

    "Stuttering study support treatment" – now there's a "headline" I find difficult to parse!

    [(myl) It's lucky, then, that it was a typo (on my part) for "Stuttering studies support treatment".]

  2. Grep Agni said,

    March 9, 2011 @ 10:51 am

    Since I can't read the paper, could someone explain how the between-clapping interval could differ between hands? Does "clapping" mean tapping a tabe or something?

    [(myl) The positions and periods of the hands were tracked separately:

    A Northern Digital Optotrak 3020 system was used to record hand movements during the clapping task. In the Optotrak system, the motion of infrared light emitting diodes (IREDs) is tracked by a set of three fixed cameras. […] Movements were analyzed in the medial-lateral dimension. The position of each IRED was sampled at 250 samples per second. […]

    Displacement records were low pass filtered in both backward and forward directions with a cutoff of 8 Hz using a fifth-order Butterworth filter. The velocity of each clapping movement was calculated using a three-point difference technique. Motions of each hand were measured separately. The starting point for each clap was defined as the point at which the velocity of the hand slowed to 3% of the peak velocity while moving toward the midline. The 3% velocity toward the midline value corresponds almost exactly to the point in time when the hands first make contact. The starting point of each clapping cycle also served as the ending point of the previous clapping cycle. A Matlab algorithm automatically computed the starting point for each clap, for each hand, on the basis of this 3% velocity criterion.

    Obviously, as long as successful clapping continued to take place, the periods can't be all that different between the hands — and the graph makes it clear that the variances as well as the mean periods were highly correlated between the hands. I suspect (without being able to prove) that a purely acoustic measure would have shown about the same results, in terms of differences between the two test groups.]

  3. Tom D said,

    March 9, 2011 @ 11:00 am

    For me, one of the most fascinating things about stuttering is that it is not just limited to the spoken mode of language–signers have been shown to stutter as well. Snyder (2009) and Whitebread (2004) give some basic background.

  4. Alan Gunn said,

    March 9, 2011 @ 11:25 am

    Until I saw "The King's Speech," I hadn't thought about stuttering for years, probably because it's been a very long time since I've heard anyone do it. Yet when I was a child, I knew several people, both adults and other children, who stuttered. It never seemed like a big deal back then. Are there data on the incidence of stuttering? Has it declined, or is my experience unusual? I tried a Google search but didn't come up with anything except a reference to "Van Riper's predicted decline in the incidence of stuttering," which cost $$ to follow up on.

  5. GeorgeW said,

    March 9, 2011 @ 1:47 pm

    Is stutter and stammer synonymous? In "The King's Speech," he was described as a stammerer.

    I think I use stutter for the kind of speech impediment described here and stammer as temporary incoherence due to fear, excitement, inebriation, etc.

    [(myl) To a first approximation, stutter is U.S. and stammer is U.K.]

  6. Martin J Ball said,

    March 9, 2011 @ 2:34 pm

    See the post on this difference (stutter/stammer) on Lynne Murphy's blog, 'Separated by a common language':

    For me they are simply US / UK different terms foe the same thing; for others, however, there appears to be a semantic difference.

  7. GeorgeW said,

    March 9, 2011 @ 4:33 pm

    myl & Martin: Yes, it seems that AmE. stutter is equivalent to BrE. stammer. However, since we (Americans) have both, we seem to have made a semantic distinction. I looked at a few samples of 'stammering' in the NYTimes. I didn't delve deeply, but, except for references to the film, it seems that (AmE) stammering is a temporary and passing condition caused by some emotional situation. Some examples from the search:

    "I was suddenly stammering out my request to Vincent Sardi himself. He was quite gracious and said he would see what he could do. "

    "After much stammering and cuteness, the pair — who met at a bar, had a one-night-stand and then didn't see each other for a month…"

    "Sweaty, stammering and hyperactive, Lemmon seemed to embody the countertype of the monumental, granite-jawed leading men of the 1950s"

    "A boy could be seen fidgeting with his baseball cap in an interrogation room, stammering as he explained that his gun had gone off accidentally, killing a classmate."

    "It leaves you stammering "ums" and "wells" as the mind races towards nothingness"

  8. Nick said,

    March 10, 2011 @ 12:05 pm

    I have a stutter. It's not as bad as my father's or my brother's, but I have one nonetheless. Three of the hardest words for me to say are "phonetics", "phonology", and "stutter". I experienced this while visiting an open house for a grad school last week. My research interests are, surprise, phonetics and phonology.

    I keep a mental list of words that cause me to stutter, and they're almost always words that have primary stress on the second syllable with some sort of voiceless segment first. I've been meaning to keep an actual catalog but I've never gotten around to it. It's usually a lot easier to pronounce a word like "phonology" with a diphthong as the first vowel rather than a reduced schwa (foe-nology).

    I can usually hold a normal conversation. I do sometimes have to do the Porky Pig trick and say a different word than the one I am stuttering over, and I can usually do this without the other person noticing, but that's harder to do when speaking in jargon (i.e. if I need to say phonology, I need to say phonology).

    As a linguist and as one who stutters, stuttering remains very interesting and I'm surprised it's as little-understood as it is.

  9. Jerry Friedman said,

    March 10, 2011 @ 5:48 pm

    I was brought up (in America) to believe that stuttering is repetition of sounds, especially initial sounds—called "part-word repetitions" according to Martin J Ball at Lynne Murphy's blog. Stammering is being unable to finish what you're saying. As a speech defect, it means stopping in the middle of a word—"blocking", according to Martin J Ball again—and in most of GeorgeW's quotations above I take it to mean anacolutha.

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