This study reanalyzed motion capture data from 13 native American Sign Language (ASL) signers and 32 hearing English speakers, who were asked to physically imitate and then describe the trajectory of a three-dimensional version of the Müller-Lyer illusion (Brown et al., 2021). Building on the previous findings that all participants were less affected by the visual illusion when actually interacting with the object or gesturing/signing while describing it than when estimating the size of the object, this study examines specific kinematic features of their gesture, focusing on smoothness, accuracy, velocity, and rhythmicity using dynamic time warping and other quantitative methods. This analysis demonstrated that signers have smoother movements during gestures about trajectory than English speakers (but not during instrumental action), have faster hand movements overall, have greater general rhythmicity in their gestures (particularly in description tasks), and are less accurate in their description of the object's trajectory than English speakers. These results suggest that there are subtle differences in the gestures produced by signers and speakers, which may indicate their engagement of different cognitive mechanisms while producing descriptive gestures. Specifically, this process seems to be more informed by action in speakers, but more by language in signers.
Naomi Scherer (Wed,) studied this question.