Physiological measures of presence in stressful virtual environments
How do higher frame rates affect presence? Keep in mind, this paper presents 3 experiments. The first experiment is repeated exposure to VE and its physiological effect. The second experiment is the first experiment in Insko's thesis. So, this experiment only highlights the last experiment, the frame rate study.
Variables and Constants
- frame rate - 10, 15, 20, 30 fps
Display-related constants such as display size, form factor, among others, were kept as constants.
- head-mounted display - a virtual research v8 head-mounted display with true vga resolution of (640x3) x 480 pixels per eye was used in both experiments. this display device consists of two 1.3-inch-diagonal active matrix lcds with an aspect ratio of 4:
- hiball head tracker sensor - this tracker works over a range of 10m by 4m with 0.2 millimeter positional resolution and angular precision better than 0.03 degree. it updates position and orientation at approximately 1.5khz. these updates are filtered over 25 ms before they are sent
- polhemus 3space 6dof tracker - for tracking of links on the participants' knees and another in a joystick held by one hand
- joystick - handheld, tracked by the polhemus
One graphics pipe of a Reality Monster, a 32-processor SGI Onyx2 computer, was used to generate the images. The pipe consists of an Infinite Reality2 Engine with four R12000 processors, four raster managers, and 64MB texture memory.
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Subjects were trained to pick up and drop blocks in the Training Room and then carried a red block to the Pit Room and dropped it on a red X-target on the floor of the Living Room, a procedural improvement that forced subjects to look down into the pit. They then plucked from the air two other colored blocks floating in the Pit Room and dropped each on the correspondingly colored Xs on the floor of the Living Room.
Interaction and Environment
Participants would move objects by attaching objects to their hands.
The virtual environment consisted of the Training Room and the Pit Room. The Pit Room consisted of a 2-foot wide virtual ledge above a 20-foot (virtual) drop to a room below containing living room furniture. There was also a chair on the wooden ledge on the far side of the room.
- heart rate - finger skin temperature, electrodermal response (galvanic skin response), and heart rate (via a three electrode electrocardiography) were measured non-invasively from the fingers of one hand using procomp+ tethered telemetry system at a rate of 32 times p
- presence - this is a substitute for skin conductance and skin temperature. these were used to measure feeling present.
There was a significant direct effect of frame rate on heart rate for a interactive experience of the ve task.
Higher frame rates led to a higher heart rate in interactive navigation of stressful VE's.
Specificity: Somewhat specific
This increased heart beat applies to stressful VE's. Additionally, the significance applied to all conditions except for 10 FPS.
There was a significant direct effect of frame rate on presence for a interactive experience of the ve task.
Higher frame rates led to higher feeling of presence (with higher skin conductance and skin temperature) in interactive navigation of stressful VE's.
Specificity: Somewhat specific
This finding does apply to stressful VE's, which in this case, was looking down at a big drop in a VE. Presence was measured with changes in skin conductance and temperature, which were strongly significant. (P < .001)