A real-time MRI examination of retroflex stops and rhotics in Tamil reveals that in some contexts these consonants may in fact be achieved with little or no retroflexion of the tongue tip. Rather, maneuvering and shaping of the tongue in order to achieve post-alveolar contact varies across vowel contexts. Between back vowels /a/ and /u/, post-alveolar constriction involves curling back of the tongue tip, but in the context of high front vowel /i/, the same constriction is achieved by bunching of the tongue. It appears that though there is a stable constriction target in the post-alveolar region, its achievement is not fixed but is instead a consequence of the variable state of the vocal tract in different vowel contexts. Articulatory configurations of the tongue across these vowel contexts were examined by comparing measures of Gaussian curvature at evenly spaced points along the vocal tract. The results support the notion that so-called retroflex consonants have a specified target constriction in the post-alveolar region, but that the specific articulations employed to achieve this constriction are not fixed, in keeping with the task dynamic model of speech production.
Bibliographic reference. Smith, Caitlin / Proctor, Michael / Iskarous, Khalil / Goldstein, Louis / Narayanan, Shrikanth (2013): "Stable articulatory tasks and their variable formation: tamil retroflex consonants", In INTERSPEECH-2013, 2006-2009.