Exploring Virtual Doppelgangers as Movement Models to Enhance Voluntary Imitation.

Virtual Reality (VR) setups offer the possibility to investigate interactions between model and observer characteristics in imitation behavior, such as in the chameleon effect of automatic mimicry. We tested the hypothesis that perceived affiliative characteristics of a virtual model, such as similarity to the observer and likability, will facilitate observers' engagement in voluntary motor imitation. In a within-subjects design, participants were exposed to four virtual characters of different degrees of realism and observer similarity (avatar numbers AN=1-4), ranging from an abstract stickperson to a personalized doppelganger avatar designed from 3d scans of the observer. The characters performed different trunk movements and participants were asked to imitate these. We defined functional ranges of motion (ROM) for spinal extension (bending backward, BB), lateral flexion (bending sideward, BS) and rotation in the horizontal plane (RH) based on shoulder marker trajectories as behavioral indicators of imitation. Participants' ratings on avatar appearance, characteristics and embodiment/ enfacement were recorded in an Autonomous Avatar Questionnaire (AAQ), factorized into three sum scales based on our explorative analysis. Linear mixed effects models revealed that for lateral flexion (BS), a facilitating influence of avatar type on ROM was mediated by perceived identificatory avatar properties such as avatar likability, avatar-observer-similarity and other affiliative characteristics (AAQ1). This suggests that maximization of model-observer similarity with a virtual doppelganger may be useful in observational modeling and this could be used to modify maladaptive motor behaviors in patients with chronic back pain.