Real-time position and head-gaze tracking. In collaboration with Winrich Freiwald, Cory Miller, David Leopold, and Xiaoqin Wang, our lab is developing methods to track marmoset position and head gaze direction in free moving animals as a paradigm to investigate genuine social interactions between group housed animals. An array of motion capture infra-red video cameras can monitor the position of marmosets to label their identities and direction of their head gaze. As seen in preliminary data this optical tracking enables us to estimate the position of marmosets as they move through three dimensional space. The unique spatial pattern of the markers also makes it possible to identify each individual and to reconstruct the direction of their head gaze in 3-D space (see estimates overlaid on the scene above). While larger primates like the rhesus macaque rely more on eye movements for orienting, smaller New World species use fast head-movements much like saccades to orient. Likewise marmosets use fast head-orienting movements, and their oculomotor range rarely extends beyond 5-10 visual degrees from the head center position of rest (Mitchell et al, 2014). Thus tracking head direction can provide accurate estimates of gaze in the marmoset, and in kind, previous studies show that, like other non-human primates, marmoset rely on head-gaze to monitor other’s attention and direct gaze following.