Methods for provoking a physiological response in a subject comprising: receiving from sensors an orientation of an HMD of the subject and a parameter indicative of a physiological state of the subject, determining a video signal representing an avatar of the subject in a virtual reality scenario to be displayed on the head mounted display taking into account the orientation of the head mounted display, wherein the video signal includes an indication of a physiological state of the avatar, and sending the video signal to the head mounted display for visualization, optionally accompanied by a suitable audio signal. During a first period, the indication of the physiological state of the avatar substantially corresponds to the measured physiological state, and during a second period the indication of the physiological state of the avatar does not correspond to the measured physiological state. Related computer program and computing systems are also disclosed.