Reference-frames, or coordinate systems, are used to express properties and relationships of objects in the environment. While the use of reference-frames is well understood in physical sciences, how the brain uses reference-frames remains a fundamental question. The goal of this dissertation is to reach a better understanding of reference-frames in human perceptual, motor, and cognitive processing. In the first project, we study reference-frames in perception and develop a model to explain the transition from egocentric (based on the observer) to exocentric (based outside the observer) reference-frames to account for the perception of relative motion. In a second project, we focus on motor behavior, more specifically on goal-directed reaching. We develop a model that explains how egocentric perceptual and motor reference-frames can be coordinated through exocentric reference-frames. Finally, in a third project, we study how the cognitive system can store and recognize objects by using sensorimotor schema that allows mental rotation within an exocentric reference-frame
