Kinematics of Negative Headshake in Seven Sign Languages

In sign languages, negative sentences are often accompanied by nonmanual markers of negation, including headshake. In some sign languages, nonmanual markers alone can express negation, without the presence of a manual negative sign. While there has been considerable research on the typology of negation in sign languages in terms of syntactic structure and co-occurrence patterns of manual and nonmanual markers, very little research has been done on kinematic properties of negative headshake and their relation to linguistic features. In this exploratory study, we analyzed kinematics of negative headshake in seven sign languages-Brazilian Sign Language, Dutch Sign Language, German Sign Language, Kata Kolok, Norwegian Sign Language, Polish Sign Language and Russian Sign Language-using naturalistic corpus data (mainly free conversations). We used manual annotation of headshakes to analyze duration, and the computer vision tool 3DDFA_v2 to analyze amplitude and velocity. We considered whether headshake kinematics differs across languages, and whether it is affected by the presence of a manual negative sign and/or by spreading of the headshake across multiple signs. In addition, we compared three zones falling under the headshake: pre-negative sign, negative sign, and post-negative sign. We found that duration of headshakes varies cross-linguistically and is affected by spreading. For amplitude and maximum velocity, we found that spreading headshakes are kinematically stronger than non-spreading headshakes, but the presence of a manual negative sign does not significantly affect these kinematic measures. For zones within headshake, we found that, in general, the negative sign zone is kinematically weakest contrary to some previous findings for Dutch Sign Language, but that there is cross-linguistic variation in how the zones affect the kinematic measures. The study presents the first ever description of headshake kinematics in naturalistic data from several sign languages, and provides a first step towards typological research into kinematics of nonmanual markers.