an alternative md-scal analysis of the graham and house data

LETTERS TO THE EDITOR

Received 18 March 1971 9.2, 9.7

Influence of Utterance Length upon Bilabial Closure Duration for/p/

MAR•I• F. SCHWARTZ

Department of Speech, Speech and Hearing Center, Temple University, Philadelphia, Pennsylvania 19122

An inverse relationship exists between the duration of the bilabial closure for/p/in the first word of an utterance and the total number of words in the utterance.

Lindblom • has observed the tendency for the duration of a stop consonant in word-initial position to vary inversely with the number of syllables in the word. The present study is concerned with whether this effect applies also to the number of words in an utterance, i.e., is there an inverse relationship between the duration of a consonant in the first word of an utterance and the total number of words in that utterance?

Data were obtained from four young adult females with normal speech. Each was seated separately in a sound-treated room and asked to make three productions of each of the following utterances: (1) /ipi/, (2)/ipi/saw/ipi/, (3)/ipi/saw/ipi/with/ipi/. The sequence of nine productions was randomized separately for each speaker.

The following procedure was used to obtain measurements of the bilabial closure duration for the first

/p/ in each utterance. A rigid walled vinyl catheter (2-mm i.d. X2.2-mm o.d.) was inserted approximately • in. into the buccal cavity at the corner of the mouth. The other end of the catheter was coupled to a pressure transducer, the output of which was conditioned and sent to an optical oscillograph for readout. The onset of the closure was associated with a sudden marked

increase in intraoral air pressure, while the offset (the plosive burst or release) was signaled by a sudden decrease in intraoral air pressure. Measurements were made to the nearest millisecond, and the three productions of each utterance by a speaker were averaged to yield a single value.

•-145 l

• 95• 1 3 5

words

FIG. 1. Bilabial closure dura-

tion for /p/ (milliseconds) as a function of the number of words in the utterance. Data are shown for each of the four

speakers.

The results are shown in Fig. 1. It may be seen that each speaker decreased the closure duration as the number of words in the utterance was increased. The

differences were statistically significant (p < 0.05). The finding suggests that the motor commands for

the initial bilabial gesture are constrained by the number of words which follow. This, in turn, suggests that a speaker "scans" ahead to appraise the length of the utterance and uses this information to determine

the amount of time he may devote to the articulation of individual sounds. Thus the inverse relationship between stop consonant duration and utterance length applies not only to the intraword condition, as shown by Lindblom, but to the interword condition as well.

• B. E. F. Lindblom, "Temporal Organization of Syllable Production," Speech Transmission Lab., RIT, Stockholm, QPSR 2-3 (1968).

Received 1 April 1971 9.5, 9.6, 9.7

An Alternative MD-SCAL Analysis of the Graham and House Data

SADANAND SINGH, DAVID R. WOODS, AND ABRAHAM TISHMAN

Howard University, Washington, D.C. 20001

Graham and House (1971) used a non-Euclidean metric (r- 1.5) to scale children's perceptual errors of 16 consonants in a four-dimensional configuration. They found that neither the Chomsky-Halle linguistic features nor traditional phonetic features were good interpretants of their dimensions. Using a Euclidean metric (r--2.0), we found a two-dimensional configuration, whose dimensions could be interpreted without misclassification as (1) stop versus continuant and (2) sonorant versus obstruent. The obstruents were further distinguished as (3) sibilant/nonsibilant along the second dimension.

Graham and House • used a nonmetric multidimen-

sional scaling technique 2-4 to analyze the structure of the errors made by children in judging pairs of phono-

logical sequences as "same" or different. The plotting of Kruskal's stress criterion against the dimensionaltry of the configurations when the Minkowski r metric was

6(:• Volume 51 Number 2 (Part 2) 1972

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1.5 suggested to them that the four-dimensional configuration accounted for about 90% of the fit. Their interpretation was based on this configuration. They were unable to interpret, however, the rank order of the sounds on any dimension perfectly in terms of feature categories. After testing both Chomsky-Halle 5 and traditional articulatory features, they concluded that "there is no completely satisfactory explanation for the way in which the sounds are ordered along the four dimensions that resulted from the nonmetric

multidimensional-analysis procedure" (Ref. 5, p. 565). Using a Euclidean metric (r=2.0) instead of the

Minkowski r metric (r-1.5), we found that a two- dimensional space could be interpreted in terms of feature categories without misclassifications in rank order. Figure 1 shows a plot of percentage stress (Kruskal's stress formula 1) as a function of the dimensionality of the configuration. The sharpest drop ("elbow") was between the one- and two-dimensional configurations. Although the percentage of stress in two dimensions (16.6%) was rather high, its interpretation was better than that of the three-dimensional configuration. No new feature categories seemed possible in the three-dimensional configuration. Table I shows the coordinates (unrotated) of the 16 sounds of the Graham and House data in a two-dimensional

Euclidean space. Figure 2 is a plotting of these points. Although the

orientation of the axes of a Euclidean space is arbitrary, it seemed unnecessary to rotate them in this case because they were interpretable in their present orientation. Dimension 1 shows all members of the stop class (/k p t n m •; d/) to the left of all members of the continuant class (/w 1 • r 0 s z j f/). Dimension 2 showed all SOhorants (/wjrmln/) together above the obstruents (/p f k d 0 t s z •; •/). Furthermore, within the obstruent group, all the sibilants (/• •; z s/) were below the nonsibilants (/t 0 d k f p/). Thus these two dimensions categorized the 16 consonants into six distinct groups: (/p t k d/), (/m n/), (/f 0/), (/•;/), (/s • z/), (1 r j w/). No feature categories were recovered to distinguish members within groups.

The above interpretation did not depend on an isomorphic mapping of linguistic binary features onto dimensions of the configuration. Instead, a dimension might be interpreted as the interaction of two binary features. Dimension 2 (Fig. 2) showed the interaction of the binary features sonorant/obstruent and sibilant/ nonsibilant. As a ternary dimension (sonorant/nonsibilant obstruent/sibilant), dimension 2 also showed the greater psychological distance between sonorants and sibilant obstruents than between sonorants and

nonsibilant obstruents. Furthermore, some linguistic features which did not appear as independent dimensions might be interpretable as combinations of cate- gores from different dimensions. For example, the nasals /m n/were uniquely specified as sonorant stops and the a•ricate/•/was uniquely specified as a sibilant stop.

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NUMBER OF DIMENSIONS

Fro. 1. Stress of configuration of 16 constants.

Our analysis eliminated the problems that Graham and House had in their interpretation of the four- dimensional configuration. Their first dimension "ap- proximates a sonorant-nonsonorant description, except for the location of /p/" (Ref. 1, p. 564). Our second dimension divided sonorants and obstruents without misclassification. Their second dimension reflected

nasality, although /k/ was out of place. We found nasality as the result of the interaction of sonorant and stop. Their third dimension was interpreted by the feature stop/continuant with the phoneme /f/ as a misclassification. Our two-dimensional space eliminated this misclassification. Their fourth dimension had three misclassifications for the feature strident. Using the related feature sibilant, we found a perfect division into sibilant/nonsibilant. This conformed to the results of Klatt 6 and our own analyses of similarities data. 7

T^BLw. I. The final configuration of 16 points in 2 dimensions.

1 2

-0.821 0.129 -0.663 -0.405 --0.278 -- 1.291 - 1.220 0.041 -0.157 --0.001 -0.393 0.755 --0.438 0.477

0.853 0.110 0.506 -0.102 0.574 --0.892 0.196 -- 1.434 0.652 --1.106 0.064 0.690 0.312 0.779 0.809 0.9s0 0.004 1.299

The Journal of the Acoustical Society of America 667


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Fro. 2. Two-dimensional configuration of 16 constants (Graham-House data).

The fact that such important features as place of articulation and voicing were not recovered from the

multidimensional configurations in either two or four dimensions might be due to the particular sample of sounds used in the Graham and House experiment. For example, the sonorants are all voiced and only two voiced-voiceless cognate pairs were included among the obstruents (/t d/),/s z/).

ACKNOWLEDGMENTS

This work was supported by a grant, NB 08544 from the National Institutes of Health. We wish to thank

Dr. Arthur S. House for a letter commenting on some questions we had.

• L. W. Graham and A. S. House, "Phonological Opposition in Children: A Perceptual Study," J. Acoust. Soc. Amer. 49, 559-566 (1971).

•-R. N. Shepard, "The Analysis of Proximities: Multidimen- sional Scaling with an Unknown Distance Function," Psycho- metrika 27, 125-140, 219-246 (1962).

a j. B. Kruskal, "Multidimensional Scaling by Optimizing Goodness of Fit to a Nonmetric Hypothesis," Psychometrika 29, 1-27 (1964).

4j. B. Kruskal, "Nonmetric Multidimensional Scaling: A Numerical Method," Psychometrike 29, 115-129 (1964).

• N. Chomsky and M. Halle, The Sound Pattern of English (Harper & Row, New York, 1968).

6 D. Klatt, "Structure of Confusions in Short-Term Memory Between English Consonants," J. Acoust. Soc. Amer. 44, 401-407 (1968).

7 S. Singh, D. R. Woods, and G. M. Becker, "Comparison of Six Feature Systems Using Data From Three Psychophysical Methods," in Perceptual Correlates of Distinctive Feature Systems II (Communication Sciences Lab., Howard Univ., Washington, D.C., 1970).

Received 1 September 1971 9.5• 9.6• 9.7

A Comment on •An Alternative MD-SCAL Analysis of the Graham and House Data"

[-S. Singh, D. R. Woods, and A. Tishman, J. Acoust. Soc. Amer. 51,666 (1972)]

ARTHUR S. HOUSE

Institute for Defense Analyses, Princeton, New Jersey 08540

LOUELLA W. GRAHAM

Georgia Retardation Center, Atlanta, Georgia 30341

The recent interest in the Graham-House report • is gratifying to us. Our delight would have been greater, however, if the interest had been stimulated by a report less vulnerable to criticism on methodological grounds. We have learned, from Singh, Woods, and Tishman, • from Pols, 3 Bricker, 3 Pruzansky, a and even from Kruskal and Wish in a public workshop 4 that the coordinates on which our data were plotted could have been rotated, probably with profit, but for our awkward decision to find a solution in a space defined by a Minkowski r of 1.5 (a metric that precludes meaningful rotation). The question also has been raised as to whether analyses that are sensitive to individual differences (using

INDSCAL, as described by Carroll and Chang, 5 for example) will improve the interpretation of our data.

The Singh-Woods-Tishman (SWT) note, however, poses some interesting issues without providing--for us at least--any satisfying answers. The two dimensions described in that analysis certainly do not provide any strong insights about cues the child uses to deduce the phonological system of his language--that is, about the nature of the perceptual realities he hears in speech. Our data indicated that the child is capable of dis- tinguishing the phonemes used in the study (and by implication at least, all the phonemes of the language) with essentially the performance of an adult. Our use

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an alternative md-scal analysis of the graham and house data

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