Aimee M. Surprenant
Dept. of Speech & Hear. Sci., Indiana Univ., Bloomington, IN 47405
Yale University and Haskins Labs., New Haven, CT
Purdue Univ., West Lafayette, IN
An experiment was conducted to evaluate the hypothesis that speakers perceive the intended gestures of the talker, not merely the sound that is carried to their ears. This is a central assumption of the revised motor theory of speech perception [Liberman and Mattingly, Cognition 21, 1--36 (1985)]. Of relevance to this hypothesis is how listeners perceive instances of consonant gestures that show extreme overlap in casual speech and that may, therefore, lack the expected correlates in the acoustic signal (so-called ``hidden'' gestures). To test this, utterances that showed varying degrees of actual gestural overlap were selected from an x-ray microbeam study investigating the production of consonant sequences. These were presented to listeners in a phoneme monitoring task. Results show that as the temporal distance between centers of overlapping gestures decreases, detection also decreases. That is, as the target gesture becomes more and more hidden by the subsequent gesture, subjects report hearing it less and less. This result is qualified by the finding that the magnitude of the gesture also decreases when a gesture is hidden. This research is a first step towards using natural utterances with known articulatory properties to investigate theories of speech perception.