Publications (3)4.23 Total impact
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ABSTRACT: The current standard for measuring cognitive workload is the NASA Task-load Index (TLX) questionnaire. Although this measure has a high degree of reliability, diagnosticity, and sensitivity, a reliable physiological measure of cognitive workload could provide a non-invasive, objective measure of workload that could be tracked in real or near real-time without interrupting the task. This study investigated changes in respiratory sinus arrhythmia (RSA) during seven different sub-sections of a proposed selection test for Navy aviation and compared them to changes reported on the NASA-TLX. 201 healthy participants performed the seven tasks of the Navy's Performance Based Measure. RSA was measured during each task and the NASA-TLX was administered after each task. Multi-level modeling revealed that RSA significantly predicted NASA-TLX scores. A moderate within-subject correlation was also found between RSA and NASA TLX scores. The findings support the potential development of RSA as a real-time measure of cognitive workload.International journal of psychophysiology: official journal of the International Organization of Psychophysiology 11/2011; 83(1):96-101. · 3.05 Impact Factor
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ABSTRACT: We examined the effects of several display characteristics of head-mounted displays (HMDs) on simulator sickness (SS). Technological limitations, such as display delay and reduced field of view (FOV), affect perception when using an HMD and are often thought to be related to SS. Few studies have examined the relationship between FOV and geometric FOV (image scale factor) or how HMD characteristics may interact. Participants made active head movements to locate objects when viewing a live video via an HMD. Compared with no added delay, an additional 200 ms of display delay did not result in increased SS, as measured by the Simulator Sickness Questionnaire. Furthermore, an effect of image scale factor on SS was not revealed. However, SS was greater when peripheral vision was occluded than when it was not. Peripheral vision moderated the effects of image scale factor and delay on head movement velocity. Occluding peripheral vision may subject HMD users to the potential detrimental consequences of HMD characteristics more than when peripheral vision of the external environment is available, resulting in more SS. Future research should investigate to what extent peripheral vision can be occluded without increasing SS and without sacrificing realism and presence. To reduce the occurrence of SS, a degree of peripheral vision of the external world should be provided. Furthermore, users and designers should be aware that head movement behavior may be affected by HMD characteristics.Human Factors The Journal of the Human Factors and Ergonomics Society 06/2011; 53(3):308-19. · 1.19 Impact Factor
Article: Perceptual thresholds for display lag in a real visual environment are not affected by field of view or psychophysical technique[show abstract] [hide abstract]
ABSTRACT: IntroductionLag between head movement and the time to render the visual consequences of the movement during head mounted display (HMD) applications presents challenges in the appearance of a stable image. This appearance of an image to “lag” behind or “swim” about may cause detriments in user performance, lack of user acceptance, and simulator sickness. These known potential consequences of HMD use motivated the current work to explore the human capability to detect display lag. The aim in this study was to gain a better understanding of the threshold for display lag detection and what variables affect this threshold.MethodsTwenty four subjects completed a repeated-measures three field of view (FOV; 10°, 38°, and full monocular) X two psychophysical technique (forced-choice and simple) experimental design. Passive sinusoidal head movements about the yaw axis were generated by an oscillating chair. A visual scene consisting of vertical bars was projected by an optokinetic drum moving in a sinusoidal fashion with the subjects. Subjects reported whether the scene lagged behind head movement.ResultsThe grand threshold mean for lag detection was 147.64 ms (SD = 84.91). The median was 130 ms and the 25th and 75th percentiles were 84.17 ms and 206.25 ms, respectively. Lag thresholds were not systematically influenced by either FOV or psychophysical technique.DiscussionNaïve subjects in the current study were less sensitive to lag as compared to thresholds reported in previous HMD studies, which provided lag detection strategies and practice [e.g., 77 ms; Ellis, Mania, Adelstein, & Hill, 2004]. Future examinations using the current paradigm should provide detection strategies and more practice.Displays.