- Differences between the real and virtual world:
The technology that is used for virtual environments is not yet capable of being unnoticed by the user. The differences between the user's experience in the virtual world and a comprable real world are of interest to all users of virtual environments. One notable difference that many laboratories have discovered is a persons perception of size and distance within the virtual environment. Space perception within a virtual environment is a very interesting topic, since it is not entirely understood how humans perceive distances within the real world. Virtual environments can be used as both a tool to investigate human space perception and, if space perception is made to be the same in the virtual world as in the real world, as a novel product that could potentially improve surgery through the use of simulators and minimize cost in design and production time for manufacturers.
- Human adaptation and transfer:
How do humans adapt in a VE? Is this different than in the real world? Humans are amazingly accurate when acting on their environment in the real world. In part this is because humans can easily adapt their actions to varying circumstances in their environment. Knowing this, I am interested in how a person will adapt their visually-directed distance judgments when given feedback in VEs. Using a treadmill VE, we have shown that recalibration of action is reflected in the real world as a result of manipulating the relation between the visual indication of
speed, presented using computer graphics, and the biomechanical speed of walking on a treadmill. In addition, it was shown that the magnitude of the optic flow does not need to vary in order for this recalibration to occur. The visual perception of self-motion is at least in part responsible for this recalibration effect (Mohler-TAP, 2007). Further research was conducted within a head-mounted display virtual environment that investigated both adaptation of a user within the virtual environment, but also transfer of this adpatation to the real world (Mohler-dissertation, 2007).
- Locomotion and gait parameters:
Does visual motion influence locomotion?
Since many actions are guided primarily by vision one must also consider how vision influences behavior in a VE. It is possible that information from visual motion is coupled to the metabolic and mechanical information for the speed of self-motion for more reliable, consistent and accurate locomotor behavior. Many scientists have questioned why humans make gait transitions and freely walk at a particular speed. While the metabolic and mechanical analyses resulting from previous research does a reasonable job of predicting the speed at which various locomotor activities occur, they do not provide a complete explanation of how these motor behaviors are initiated or sustained as a person moves through the world. We explored the visual influence on these locomotor behaviors by using a treadmill VE. Using a virtual hallway the visual speed was easily manipulated. Visual speed was found to affect both the speed of the gait transitions and the speed of free walking (Mohler-EBR 2007). From an engineering viewpoint, this immediate change in behaviors as a result of vision (without user awareness) could be used as a tool when designing VEs.
In addition, recently I have evaluated the gait parameters for a person who is walking with eyes open versus eyes closed and wearing a head-mounted display versus in the real world. There were two main finding from these results. First, people walk slower when their eyes are closed and when they are wearing a HMD and a backpack than they do when they are walking in the real world and are unrestricted. Second, when people have a HMD on and are looking at the visuals their head-trunk angle is significantly higher than in all other conditions for the same task (Mohler-EGVE, 2007).
- Self-motion perception:
The illusion of self-motion is one that many of us have experienced while sitting on a stationary train and seeing another train moving in the oppositive direction. However, this illusion is not easily replicated or controlled in an experimental setting. VEs would be much easier to implement if we could fool the user into believing that they are moving without having expensive technology to actually move them. Vection refers to the sensation of self-motion elicited by a moving visual stimulus. Vection percepts are commonly divided into circular vection, associated with rotational motion around a vertical axis centered on the viewer, and translational vection, involving straight-line movement. A frequently discussed occurrence of linear vection occurs when a person sitting in a stationary vehicle views another vehicle in motion and incorrectly perceives themselves to be moving. A large screen VE was used to induce the perception of translational and rotational self-motion. Two aspects of this problem were explored. Our first study found that the level of visual immersion (seeing a reference frame) affects subjective measures of linear vection, but not circular vection. Our second study describes a novel way (measuring running-in-place drift) in which to measure the effectiveness of displays intended to produce a sense of vection (Mohler-APGV, 2005). My research has evaluated both circular and linear vection towards the goal of finding a low-cost engineering solution that can create the illusion of rotational and translational self-motion.
