Undershoot of ASL Locations in Fast Signing
Claude E. Mauk
University of Pittsburgh
Bjorn Lindblom
Stockholm University & University of Texas at Austin
The current study successfully applies methodologies used to investigate undershoot in
speech to an investigation of undershoot in a signed language. Phonetic undershoot is the
failure of a phonetic gesture to achieve an articulatory or acoustic target associated with it.
The Hypo- & Hyper-articulation (H&H) model of speech production (Lindblom 1990) views
speech as a motor activity that is subject to the constraint of economy of effort. That is, if
there is no motivation to the contrary, speech will tend toward a reduced form, i.e. hypoarticulation.
Researchers have examined undershoot by comparing fast and normal speech (e.g. Gay 1978)
and comparing normal and clear speech (e.g. Moon 1991), often focusing on variation in
vowel quality. Moon, for example, found that vowels in regular speech are hypo-articulated
relative to vowels in clear speech. Similarly, undershoot effects have been found for F2 onset
values in the articulation of English stop consonants (e.g. Tjaden & Weismer 1998, Mauk
2003).
Few researchers have studied phonetic effects such as undershoot in signed languages.
Cheek (2001) examined variation in the ASL index hand caused by the proximity of a 5hand. She analyzed the index handshapes in both normal and fast signing and found that
signing rate was a factor in the degree of variation in the handshape measure. Mauk (2003)
found similar results looking at the 5 and index handshapes over a range of signing rates.
The current experiment will compare location values for neutral space signs and forehead
located signs across a range of signing rates. The location of the hands in space during
signing may be analogous to the location of the tongue in the mouth during speech,
consequently it may be expected that extreme contrasts of location will be difficult to execute
as signing rate increases. As a result, signers may undershoot the location of one or more
signs.
The data for this experiment were collected using a three-dimensional movement tracking
system, Vicon by Oxford Metrics. This kind of optoelectronic imaging system allows
markers on a participant’s body to be tracked in three dimensions simultaneously, without the
limitations of traditional video. Vicon has been used successfully in several studies of ASL
phonetics (Mauk 1999, Cheek 2001, Cormier 2002, Mauk 2003).
Four native signers of ASL were asked to sign sets of sequences composed of three signs
each. These sequences constitute four combinations of neutral space signs and forehead
signs. For example, the sign sequence shown in figure 1 contains a neutral space sign
CHILDREN preceded and followed by the forehead located sign SMART. As signing rate
increases, the location value for one or more of the three signs may be reduced. That is, in
order to complete the sign sequence in a shorter amount of time, the signer may raise the
neutral space sign or lower the two forehead signs. Figure 2 shows mean vertical location
measurements for this sequence from one participant. Note that the location of the neutral
space sign CHILDREN rises with each successive rate category, while the forehead locations
remain stable.
This general trend of stability of the forehead location and variability of the neutral space
location is true for all three of the four participants in this study. I suggest that the stability of
forehead located signs is related to the need for contact (or at least close approximation)
between the hands and the body location.
The speech and sign articulators are dissimilar in physical form. Meier (2002) lists several
ways that the articulatory systems of the two modalities differ, but suggests that while these
differences may be great, the organization of motor systems in general may lead to
commonalities in the articulation of language in the two modalities. The results of this study
suggest that a phenomenon related to production constraints, i.e. rate- and context-dependent
target undershoot, is common to both modalities.
Figure 1: ASL Sign Sequence SMART CHILDREN SMART
Figure 2: Mean location values for Forehead-Neutral-Forehead sequence, signer AY
References
Cheek, Davina Adrianne. 2001. The phonetics and phonology of handshape in American Sign Language. Ph.D.
dissertation, University of Texas at Austin.
Cormier, Kearsy. 2002. Grammaticization of Indexic Signs: How American Sign Language Expresses
Numerosity. Ph.D. dissertation, University of Texas at Austin.
Gay, Thomas. 1978. Effect of speaking rate on vowel formant movements, Journal of the Acoustical Society of
America, vol. 63, 223-230.
Lindblom, Björn. 1990. Explaining phonetic variation: A sketch of the H & H theory. Speech Production and
Speech Modeling. Ed. by W. J. Hardcastle and A. Marchal. Dordrecht. Netherlands: Kluwer Academic
Publishers, 403-439.
Mauk, Claude. 1999. The Interaction of Sign Size with Phonological Form in American Sign Language. ms,
University of Texas, Austin.
Mauk Claude E. 2003. Undershoot in two modalities: An examination of fast utterances in English and
American Sign Language, Doctoral dissertation, University of Texas, Austin.
Moon, Seung-Jae. 1991. An Acoustic and Perceptual Study of Undershoot in Clear and Citation-Form Speech.
Ph.D. dissertation, University of Texas at Austin
Tjaden, Kris and Gary Weismer. 1998. Speaking-Rate-Induced Variability in F2 Trajectories. Journal of
Speech, Language, and Hearing Research 41:976-989.