Tongue movement kinematics in speech:Task specific control of movement speed

Anders Löfqvist

Haskins LaboratoriesNew Haven, CT

Movement velocity in speech production

• speaking rate• stress• shape of velocity profiles• relationship between amplitude and peak velocity

This presentation addresses a different topic, length contrasts.

The measure of speed takes into account both the horizontal an vertical velocity of a movement:

( ˙ x 2 ˙ y 2)

Length contrast in JapaneseWhen a speaker of Japanese produces the words “kami” and ‘kammi”, the lips are closed for about 60 ms when the consonant is short, and for about 125 ms when the consonant is long.

Short

Long

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YK YM KN SO TT

ms /kami, kammi/Closure duration

Subject

Question 1: Lip-tongue coordination

In producing a sequence of vowel-labial consonant-vowel, a speaker has to do two or three things:

1. Close and open the lips for the consonant.2. Move the tongue from the position for the first vowel to that for the second vowel.3. If the consonant is voiceless, open and close the glottis

If the duration of the labial consonant in such a sequence is changed, how is the tongue movement between the two vowels affected? What happens to the interarticulator programming of lip and tongue movements?

LipsJawTipBladeBody

1 cm

1 cm

FrontBack

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Subject YK /kami/

Tongue movement from the first to the second vowel in the word ‘kami/

Hypotheses

If the duration of the oral closure for the consonant is increased, a speaker can in principle use two strategies for the coordination of the tongue and lip movements.

Closure duration: 65 ms

“kami”

a

i

Tongue body movement from first to second vowel

Closure duration: 119 ms

“kammi”

?

1.Make the same tongue movement trajectory for a long and a short consonant. Such a strategy could have one or two versions, or a combination of them.

1a. The onset of the tongue movement might be shifted later relative to the oral closure, so that the tongue movement reached its position for the second vowel at the same point in time for the long and short consonant.

i

a

Closure

“kammi”

1b. Alternatively, the onset of the tongue movement could have the same temporal relationship to the consonant closure. In this case, the interval between the offset of the tongue movement and the release of the oral closure for the labial consonant would thus increase for the long consonant. Another possibility is to shift both the onset and offset of the tongue movement.

Closure

“kammi”

a

i i

a

Closure

“kammi”

2.Modify the tongue movement during the long consonant, so that the relative timing between the tongue movement and the lip movements for the oral closure of the consonant would be more or less the same for the long and short consonants. This would imply making a slower tongue movement trajectory for the long than for the short consonant.

Closure

“kammi”

a

i

Results

Tongue movement durationFor most subjects and words, the duration of the tongue body movement from the first to the second vowel is longer in the long than in the short consonant.

Duration of the of the tongue body movement from the first to the second vowel

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YK YM KN SO TT

ms /kami,kammi/

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ms /kamee,kammee/Short

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/kema,kemma/ms

Results, ctnd

Tongue movement pathThe magnitude of the path of the tongue body movement from the first to the second vowel did not vary systematically with consonant length within or across speakers.

Any difference in movement paths was not related to a consistent change in movement onset or offset position.

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/kami,kammi/mm

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/kamee,kammee/mm

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Subject

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/kema,kemma/mm

Path of the tongue body movement from the first to the second vowel.

Results, ctnd

Average speed of tongue movementOverall, the average speed of the tongue body movement from the first to the second vowel is slower for the long than for the short consonant.

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/kami,kammi/mm/s

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/kamee,kammee/mm/s

Subject

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YK YM KN SO TT

/kema,kemma/mm/s Short

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Average speed of the tongue body movement from the first to the second vowel

Conclusion

It was hypothesized that a speaker could use one of two possible strategies of interarticulator programming if the duration of the consonant was increased. In one of them, the tongue movement trajectory would be similar for the long and short consonants; thus, the timing between the lip and tongue movements would change. In the second one, the tongue movement would be modified for the long consonant, thus resulting in a similar coordination of lip and tongue movements for both the long and short consonants. The present results clearly support the second strategy. However, the speed change did not result in the tongue movement duration for a long consonant being about twice the duration of that for a short consonant.

Question 2. Tongue kinematics in long and short consonants

HypothesisA speaker is constrained in producing lingual consonants to maintain the contact between the tongue and the palate. If the duration of the oral closure for the consonant is increased, a speaker must maintain the contact between the tongue and the palate. To do this, the speaker can in principle use two strategies for controlling the tongue movement, both of which involve modulating the speed of the tongue movement. • momentarily stop the tongue from moving. • slow down the tongue movement for the long consonant.

Of these two possibilities, the second one is the most likely, since a large body of research on tongue movements in speech suggests that the tongue hardly ever stops moving during lingual consonants, with the speed and magnitude of the movement influenced by context.

Results

I.Is the average speed of the tongue movement during the consonant slower for a long than for a short consonant?

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DS EH KE MY YI

mm/s

Voiceless stop /t/

mm/sVoiced stop /d/

Subject Subject

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Average speed of tongue tip movement during oral closure

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DS EH KE MY YI

Yes, for the tongue tip…

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DS EH KE YI

mm/s

Voiceless stop /k/

mm/s

Voiced stop /g/

Subject Subject

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Average speed of tongue body movement during oral closure

…and also for the tongue body!

Conclusion

Japanese speakers consistently reduce the speed of the tongue movement during a long compared to a short consonant. However, in no case did the tongue come to a complete stop. The path of the tongue movement during the consonant tends to be longer for long than for short consonants.

Overall conclusions

These result show that speakers of Japanese systematically modulate the speed of tongue movements in producing long and short consonants. In no case did these modulations result in a the tongue coming to a complete stop, most likely due to a general principle of cost minimization in movement control.

Now what?

• examine the relationship between speed and curvature for jaw and tongue movements

• perturb the lips in a sequence of vowel-bilabial stop-vowel and examine possible lip-tongue linkages

Acknowledgments

I am grateful to Mariko Yanagawa for help with the Japanese material and running the experiments. This work was supported by Grant No. DC-00865 from the National Institute on Deafness and Other Communication Disorders, National Institutes of Health.