A new approach shifts the concept of Presence from the original “being there” to a physical and mental state, in which the user perceives “realistic” stimuli from the Virtual Environment (VE). A strong relation between mental and bodily processes has been proofed. In particular, the central nervous System (NCS), through the Autonomic Nervous System (ANS), acts as an interface between the external environment and the internal environment of our body, controlling the activities of the internal organs, like heart contraction and rate, sweat glands activity, skin temperature and so on; typical responses for stress situations are increasing in the heart rate, increasing of the electrodermal activity, inducing rapid and shallow breathing. As a consequence, we can think of using the physiological responses as an evaluation method of the Presence level in VR. Recording “realistic” physiological responses during a virtual experience could mean that the subject had a mental state similar if he/she was in an equivalent real environment. This leads to design the systems in a way to induce to the subjects “realistic” behaviour in the VE. A t UCL, we are using the ProComp Infinity device, by Though Technology Ltd, to record the ElectroCardioGram (ECG) at 256 Hz and Galvanic Skin Response (GSR) and respiration at 32 Hz. The device is connected to the VR system using a VRPN driver, that allow us to access through the network to the data streaming, coming both from the physiological sensors and the tracking sensors in the VR system. Analysis are made in time and frequency domains, comparing the results trough different sessions and conditions in the same study. An analysis in the neighbour of some particular events is on going, to see if a characterization of the physiological behaviour is possible. The actual signals we analyse are Heart Rate (HR), obtained from the ECG and the GSR. For the first one, an important analysis is the Heart Rate Variability (HRV) evaluation, in time and frequency, comparing the values for the different conditions of the experiment. For the second one, the statistical analysis of the Skin Conductance Responses (SCRs), the peaks in the SGR variation, is a good evaluator of the level of stress. |