Oral-facial kinematics and configuration drive asymmetries in visual vowel perception

Masapollo, Polka, and Menard (2016) have recently reported that adults show robust directional asymmetries in unimodal visual-only vowel discrimination: a change from a relatively less to a relatively more peripheral vowel (in F1-F2 articulatory vowel space) results in significantly better performance than a change in the reverse direction. In the present experiments, we examined the nature of the information that is critical to elicit these asymmetries. Toward this end, we created schematic analogues that retained the isolated kinematics (spatial direction and motion) and/or configuration (global shape) of the lips of Masapollo et al.’s model speaker. We found that subjects showed asymmetries while discriminating dynamicpoint-light displays that specified both the kinematics and configuration of the speaker’s lips (Experiment 1). Moreover, this directional effect was not dependent on subjects’ knowledge that the point-light stimuli were based on distal articulatory movements (Experiment 2). In contrast, ...