The gestural and temporal organization of assimilation

Abstract

Ever since Wang and Fillmore [J. Speech Hear. Res. 4, 130 (1961)] phoneticians have distinguished between nonpredictable language‐specific speech habits and predictable universal articulatory constraints, the former being cortical and extrinsic to the vocal tract, the latter intrinsic to the vocal tract and the consequence of articulation mechanics. Assimilation came to be seen as an intrinsic vocal tract process, explained in terms of Öhman’s model of coarticulation [ 151 (1966)]. This contrasts with classical phonetics where assimilation is the result of preplanned reorganization of articulation. The work reported in this paper favors the classical view. Gestures involved in an assimilation are initiated earlier, delayed, or are held longer, than in nonassimilated situations. It is argued that this revision of gesture timing in relation to adjacent activity is an expression of preplanning of motor commands that takes place in the cortex where there is access to larger portions of the utterance (the subcortical motor structures have limited access and cannot advance or delay gestures). Examples of palatalization of Bulgarian apico‐alveolar stops and Swedish palatovelar stops are presented. The data are analyzed from x‐ray motion films by procedures described by Wood [J. Phon. 19, 281 (1991)].