INFLUENCE OF ARTICULATOR AND MANNER ON STIFFNESS Kevin D. Roon 1,2 , Adamantios I. Gafos 1,2 , Phil Hoole 3 , Chakir Zeroual 4,5 1 New York University, Dept. Linguistics; 2 Haskins Labs; 3 IPS, Munich University; 4 University Sidi Mohamed Ben-Abdellah-Morocco; 5 Laboratoire de Phonétique et Phonologie, Univ. Paris III Email: kdroon@nyu.edu ABSTRACT Comparatively little is known about the role that the speed of different articulatory movements plays in speech production. Using 3D Electromagnetic Articulography, the present experiment analyzes articulatory data from Moroccan Arabic for independent influences of oral articulator and manner on stiffness, an important property of articulator movement. Tongue back movements were found to have lower stiffness than those of the tongue tip or lower lip. No differences based on manner were found. Relevance to phonetics and phonology is discussed. Keywords: stiffness, manner, primary articulator, electromagnetic articulography, Moroccan Arabic. 1. INTRODUCTION Knowledge about the speed of various speech movements—especially, how “quick” one articulatory movement is compared another—is crucial for a better understanding of the temporal aspects of speech production, yet relatively little is known about this in articulatory phonetics. An important task is to determine the relevant measures of the speed of articulatory movements. The peak velocity achieved during movement is one possibility. It is not an ideal measure, however, since in experimental data [9] and some models of speech production [14], an articulator’s peak velocity increases with physical displacement. Stiffness is a measurement of articulator movement that characterizes speed independent of its displacement, defined in (1) in section 2.4 below. In the motor control literature, it is an abstract control parameter with a complex of consequences in the time-space behavior of the system [7]. For an intuitive idea of what stiffness is, imagine two springs alike in all aspects other than the material they are made of. If each spring is extended the same distance, the one that returns to its resting position faster has higher stiffness. Browman and Goldstein [4] speculated that stiffness “could be the basis for natural classes… [G]estures for stops…might be stiffer than those for fricatives”. Some authors have also speculated that there may be a relationship between stiffness [3] or velocity [12] and specific articulators. Little phonetic research has been conducted to see whether these speculations are supported. The relative speed of articulatory movements has received recent attention in phonology. It has been argued that articulatory velocity differences between consonants in a cluster result in differences in overlap, causing different patterns of place assimilation [12], but a precise notion of velocity is not formally spelled out. Stiffness may be the relevant property in these cases. Stiffness is formally incorporated into the task- dynamics model used in Articulatory Phonology [2], and is the parameter that has the greatest effect on the duration of articulator movement [5]. Manipulating stiffness has the effect that gestures with higher stiffness result in shorter duration movements [14]. Researchers have investigated the role of stiffness in various prosodic effects, including final lengthening [8], gestural timing across prosodic boundaries [5], and intonation [1]. Stiffness may also be a crucial consideration for production models of coarticulation, e.g. DAC of Recasens et al. [15]. 2. EXPERIMENT Given the importance of stiffness to phonetics and phonology, the present experiment used articulatory data from a larger study of Moroccan Arabic to determine whether primary oral articulator and manner of articulation were reliable influences on stiffness of articulator movement. 2.1. Participants Two male native speakers, ages 38 and 28, of the Oujda dialect of Moroccan Arabic were recorded. 2.2. Materials All stimuli were real words presented in Arabic script within a carrier phrase. The carrier phrase ICPhS XVI ID 1308 Saarbrücken, 6-10 August 2007 www.icphs2007.de 409