week 10 summaries

Variations in Physiological Responses of Participants during Different Stages of an Immersive Virtual Environment Experiment


This paper explicitly seeks for the effect of exposure in VE along the VE experience. The authors explain the physiological measures they adopted and what their changes mean: Heart Rate, Low Frequency Heart Rate Variability, and High Frequency Heart Rate Variability. The experiment was constructed as following. The subjects are introduced to training sequence to move around in VE with joystick to get familiar with VE. Then, in the experiment sequences, the subjects were to move around VE while avoiding the contact with other virtual characters in VE. 40 subjects were divided into 4 different categories with the same gender ratio. The independent variables that divided subject groups were texture quality of environment and visual aspect of the characters. Repetitive texture had 20 textures repeated twice on buildings and non-repetitive texture had 40 textures that are not repeated. There were 2 aspects of characters: cartoon-like characters and realistic characters. The subjects were asked to signal when they felt break in presence. The authors implemented DIVE with support of spatially immersive system in CAVE-like environment.

The whole experiment including training was divided into 4 time segments: baseline, training, experiment segment 1, and experiment segment 2. The authors divide the experiment into two time segments and analyze the difference between segments to see how physiological reaction changes over the time of exposure to VE. Comparing baseline with training showed that the subjects had increase in LF/HF ratio which implies increase in mental stress level. In E1, LF/HF ratio and mean HR decreases. In E2, the mental stress level and physical stress level increases. The study implies that the mental stress increases at first exposure to VE and then it drops as the user gets familiar with it. The results also suggest that the aspect of virtual character and the texture level is correlated to the level of presence.


Physiological Measures of Presence in Stressful Virtual Environments


This paper desire to see the effect of virtual event in the subject’s physiological responses. The experiment is consists of two stages in order to reduce the orienting effect that results into the increase in HR when subjects are introduced to new environment. In training room, there is nothing special. In pit room, there is a hole in the floor which leads to a virtual drop of 20 feet below if subjects move off the walkway. The authors adopted 3 physiological measures to test their hypothesis: the change in HR, the change in Skin Conductance, and the change in Skin Temperature.

The authors designed 3 different experiments to observe various effect of VE. The first experiment was designed to see the effect of repeated exposure to VE. The authors measured the level of stress the subject felt during the VE over the same 12 VE experiences. The task was to move a book from training room on a virtual chair in the pit room. The second experiment was aimed to see the effect of passive haptics in accordance with VE. In one condition, the walkway in pit room was covered by 1.5 inch wooden ledge. In another condition, the pit room was just plain floor. The authors investigated the effect of passive haptics in level of stress. The third experiment test out how the frame rate of VE affects the users. The subjects were to pick up a red block and drop the block on a red X-target in pit room. The subject group was divided into 4 with regard to the frame rate: 10, 15, 20, and 30.

The results show that the repetitive exposure results in the decrease of stress level. The passive haptics induced by 1.5 inch ledge resulted in the increase of stress level. The 10 frame rate experiment resulted in abnormal increase of stress level that is due to the discomfort and reduced temporal fidelity. In other frame rates, the stress level increased as the frame rate increased. The authors also say that the change in HR is great measure of presence, but it may work only for the VE experiences including stressful events.


The Uncanny Valley: Effect of Realism on the Impression of Artificial Human Faces


The authors start the paper with describing the uncanny valley concept that people start to dislike the robots with extremely human like visual aspects. The authors implement the experiment on human faces. In the beginning, the hypothesis was not to find the valley in this experiment. The stimuli were generated from mixing two different images with different ratios. The authors conduct series of experiment to see the effect of realism of human face.

In the first experiment, the subjects were shown 4 types of morphing sequences. The artificial face was gradually morphed to real human face by mixing two images. In result, none of the sequences showed that an almost perfectly realistic human face was a condition for the uncanny valley while each sequences showed different tendencies.

In the second experiment, the subjects were shown different types of morphing sequences with different morphing ratio for each eye and head. The uncanny valley was detected in result when the eyes and head morphing ratio is mismatching to each other.

In the third experiment, the authors tested the effect of abnormal eye sizes in the impression of the face. The subjects were shown the faces with eye sizes increased up to 150%. The artificial faces did not generate the unpleasant impression but the realistic faces did generate the unpleasant impression with larger eyes. Thus, this result showed the uncanny valley.

In the last experiment, the authors used human-like dolls to produce the same images with the third experiment. The morphing with 100% eye size did not show the uncanny valley but the morphing with 150% eye sizes showed the uncanny valley. The experiment also showed that as the face gets more real, the abnormal eyes make human find the face more uncomfortable.

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