  Movement synchrony refers to the dynamic temporal connection between the
motions of interacting people. The applications of movement synchrony are wide
and broad. For example, as a measure of coordination between teammates,
synchrony scores are often reported in sports. The autism community also
identifies movement synchrony as a key indicator of children's social and
developmental achievements. In general, raw video recordings are often used for
movement synchrony estimation, with the drawback that they may reveal people's
identities. Furthermore, such privacy concern also hinders data sharing, one
major roadblock to a fair comparison between different approaches in autism
research. To address the issue, this paper proposes an ensemble method for
movement synchrony estimation, one of the first deep-learning-based methods for
automatic movement synchrony assessment under privacy-preserving conditions.
Our method relies entirely on publicly shareable, identity-agnostic secondary
data, such as skeleton data and optical flow. We validate our method on two
datasets: (1) PT13 dataset collected from autism therapy interventions and (2)
TASD-2 dataset collected from synchronized diving competitions. In this
context, our method outperforms its counterpart approaches, both deep neural
networks and alternatives.
