In collaboration with Jason Babcock (Positive Science), we developed a head-mounted eye-tracker for fully mobile infants, children, and adults. We use the eye-tracker in studies of reaching, locomotion, and social interaction to record where people direct their gaze as they interact with objects and other people and as they navigate the environment. We use remote eye-tracking (SensoMotoric Instruments) to test where people direct their gaze while watching video.