This picture shows a setup of a virtual reality study in Prof. Gamer's research group. The participant can observe the virtual world via a head-mounted display and can move around by walking on a locomotion platform. With such setup, we currently study human defensive behavior by placing the participant in a scenario that includes potential threats such as heights, animals or other persons. By allowing relatively unconstrained behavior, such setup is ideally suited to observe naturalistic behavior and physiological responses while at the same time permitting experimental control.