The influence of visual flow and perceptual load on locomotion speed

Visual flow is used to perceive and regulate movement speed during locomotion. We assessed the extent to which variation in flow from the ground plane, arising from static visual textures, influences locomotion speed under conditions of concurrent perceptual load. In two experiments, participants walked over a 12-m projected walkway that consisted of stripes that were oriented orthogonal to the walking direction. In the critical conditions, the frequency of the stripes increased or decreased. We observed small, but consistent effects on walking speed, so that participants were walking slower when the frequency increased compared to when the frequency decreased. This basic effect suggests that participants interpreted the change in visual flow in these conditions as at least partly due to a change in their own movement speed, and counteracted such a change by speeding up or slowing down. Critically, these effects were magnified under conditions of low perceptual load and a locus of attention near the ground plane. Our findings suggest that the contribution of vision in the control of ongoing locomotion is relatively fluid and dependent on ongoing perceptual (and perhaps more generally cognitive) task demands

Vision and virtual environments

This chapter is intended to provide the reader with knowledge of the pertinent aspects of human visual processing that are relevant to virtual simulation of various environments. Before considering how real-world vision is simulated, it is perhaps prudent to review the kinds of information that are usually extracted by the visual system. It would, of course, be fruitless to provide visual detail that is rarely or never available to the senses, and it may be fatal to the endeavor to omit detail that is crucial. Thus, an overview of normal visual capabilities and idiosyncrasies is provided in Section 3.2. Section 3.3 reviews some of the ways that perceptual systems provide shortcuts to simulating the visual world. The existence of these phenomena allows system developers to compensate for hardware shortcomings with user inferences. One of the most exciting advantages of virtual environment (VE) technology is that it allows a more elaborate and complex interaction between the VE and the observer. Section 3.4 reviews a number of the ways in which we interact with the world and how these mechanisms might augment and detract from virtual simulation. After the discussion of what vision entails, a discussion of techniques that use 2-D renditions of the visual world to simulate normal viewing of the 3-D world is provided in Section 3.5. The emphasis here will be to address the design requirements of VE displays and to determine if existing displays are machine or observer limited. Considering what is optimally required by the user, a review of the adequacy of existing visual displays is also provided in Section 3.6. Suggestions are made as to how existing limitations might be overcome and speculations are made concerning what new technology might allow in Section 3.7