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Article Excerpt
INTRODUCTION
Virtual reality (VR) technology has significant potential to create advances in a number of fields, such as medicine, engineering, design, training, and entertainment; however, systematic human factors research is needed to realize this potential (Stanney, Mourant, & Kennedy, 1998). More specifically, there is a broad need for direct comparisons of human behavior in virtual and real environments (Stoffregen, Bardy, Smart, & Pagulayan, 2003).
VR technology is a promising tool for occupational safety research. It may allow researchers to safely study humans in simulated dangerous work environments. For example, very few empirical studies have addressed fall hazards on roofs and scaffolds because of the associated risk of study-related injury, but a virtual model of height will allow such research without endangering human participants. Successful applications of this model, however, require comprehensive evaluation of VR model effectiveness.
Humans detect and recognize elevation and exposure to elevation exclusively by available visual information. Elevation in the environment is perceived by the observer as a vertical distance from the surface of support to a lower surface--that is, height perception is a special case of depth perception (Gibson & Walk, 1960). Exposure to elevation may induce a psychological effect of fear of falling, leading to physiological and behavioral protective responses and a degradation in human balance control.
Human responses to height have been studied in infants and young children, using the classical "visual cliff" experimental paradigm (Gibson & Walk, 1960). Acrophobia research has suggested that the level of experienced anxiety in a specific height exposure depends on the perception of danger, which is a function of the perceived risk of falling and the severity of the expected injury (Menzies & Clarke, 1995). The risk of a fall from elevation might be mediated by a number of factors, including posture and task, distance to the elevated edge, stability of the support surface, and availability of fall-protective devices (Hsiao & Simeonov. 2001). The perceived severity of injury from a fall is affected mainly by the fall height, body mass, expected body orientation at impact, and type of the surface to be impacted (Warner & Demling, 1986). The psychological effect of fear of falling may trigger corresponding physiological responses, including an increase in heart rate (Emmelkamp & Felten, 1985). Personal danger perceptions are mediated by individual experiences and can be significantly reduced by habituation (Zimolong, 1985).
Human responses to height in virtual environments have been evaluated in research on the treatment of acrophobia (Hodges et al., 1995) and research on "presence" in immersive virtual environments (Meehan, Razzaque, Whitton, & Brooks, 2003; Regenbrecht, Schubert, & Friedman, 1998). These studies recorded a range of fearful reactions and physiological responses in both acrophobic and normal, healthy participants. However, it is still unclear whether the fearful responses from exposure to real and virtual heights are comparable. Recently, Emmelkamp et al. (2002) found that virtual height exposure is at least as effective as real height exposure for treatment of acrophobia. Rothbaum, Hodges, Anderson, Price, and Smith (2002) reported similar outcomes in treatment of fear of flying. These research findings suggest that exposures to real and virtual height have comparable therapeutic effects on acrophobic participants. However, height effects in real and virtual environments have not been comparatively evaluated in healthy, nonacrophobic participants.
Previous research has shown that exposure to height can affect a person's balance because of degraded visual stabilization (Bles, Kapteyn, Brandt, & Arnold, 1980). The distant scenes at elevation are not effective as visual references, and body sway increases (Lee & Lishman, 1975; Paulus, Straube, & Brandt, 1984). In addition, the destabilizing effect of height is significantly amplified under more challenging support conditions--that is, on deformable (Simeonov & Hsiao, 2001) or sloped surfaces (Simeonov, Hsiao, Dotson, & Ammons, 2003). However, it is not known if these effects can be adequately simulated in virtual environments of elevation.
Finally, prolonged exposure to VR can cause cybersickness (Kennedy & Lilienthal, 1994), which has been associated with postural instability (Riccio & Stoffregen, 1991). However, most of the previous research evaluated postural stability only before and after VR exposure (Cobb, 1999). The destabilizing effects of real and virtual environments of elevation have not been comparatively evaluated.
The objective of this study was to evaluate the effectiveness of a height simulation by a surround-screen virtual reality (SSVR) system as a tool for modeling elevated workplaces in occupational safety and fall-prevention research. Based on previous experimental studies (Bles et al., 1980; Emmelkamp et al., 2002; Meehan...
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