Signing amplitude and other prosodic cues in older signers: Insights from motion capture from the SignAge Corpus

Sign languages corpora of LSFB (Meurant 2015) and LSQ (Parisot & Rinfret 2015; Luna 2015) include data from elderly signers. Parisot (2017) has given more details about the analysis of verb agreement in the senior LSQ signers suggesting that “ even if verb agreement is sometimes difficult to perceive in seniors’ productions, it seems to be rather a phonetic difference than a morphosyntactic one”. Our SignAge corpus of interactions between elderly deaf signers in LSF aims to test motion capture systems to complement analysis on the basis of video recordings. Motion capture has the advantage to capture three-dimensional data, including the possibility to change the point of view. It also allows to extract more abstract movement descriptors such as speed or acceleration of the different body parts. Furthermore, it is a step forward to get semi-automatic annotation since manual annotation is time consuming. We could not use a mocap system with many reflective markers and infrared cameras in a mocap studio and we needed a less invasive mocap setting. Then, we conducted complementary tests with Kinect and Inertial Measurement Unit sensors which permit measuring acceleration and relative position differences on xyz axis. Following some of the steps from the methodological protocol developed in CorpAGEst ( http://corpagest.org/ ), we tried to involve relatives or friends as interviewers; the 13 participants they interviewed are over 65 years old (Table 1) and use LSF as their main language in everyday life. Two deaf ‘complices’ conducted 6-min interviews on the themes of the evolution of transport, access to care, culture and new technologies (Fig. 1 and our companion paper for technical details). We explore gestural flow with a kinesiological model based on linguistics and we are currently analysing i) the variation of the signing amplitude per each degree of freedom, ii) the global movement quantity and iii) the way it is correlated with which articulatory segment is concerned, in each of the three age groups in our sample. One of the hypothesis is that the ranges of motion of degrees of freedom are reduced for elderly people compared to younger people. Consequently, the transfer of the movement is much more present than for the younger. The same for finger selection: the ratio of the inertial mass between the hand and the forearm is lower for elderly than for younger people. This fact exerts a motion further on the forearm and a smoother gesture. We expect also two tendencies: the signs which clearly respond to a proximal-distal flow engaging the arm, the forearm and the hand in the movement should show proportionally less movement on the hand than we have for younger people; for the signs which clearly respond to a distal-proximal flow engaging the hand and the forearm, the movement of the forearm should be more developed than the ones of the younger people. We will present some preliminary results and the contrast between elderly and younger people (inside the panel) is reinforced in each interaction when the interviewer is the younger signer.