Journal of Experimental Psychology General · 1992 · 11 citations · 0 references
MedicineVision ScienceSpatial VisionVisual PerceptionOptical FlowVisual NavigationVisual PathwaysVisual SystemWayfindingWayfinding Cues
People navigate cluttered environments effortlessly, and two proposed mechanisms—differential motion parallax (DMP) and optical flow (IOF)—have been examined. The study asks how people achieve this wayfinding. Evidence shows that differential motion parallax, not optical flow, guides wayfinding during natural gait, with optical flow being susceptible to aliasing artifacts and lacking psychological reality.
People find their way through cluttered environments with ease and without injury. How do they do it? Two approaches to wayfinding are considered: Differential motion parallax (DMP) is a retinal motion invariant of near and far objects moving against fixation; the information in optical flow (IOF) is a radial pattern of vectors, relying on decomposition of retinal flow. Evidence is presented that DMP guides wayfinding during natural gait, accounting for errors as well as correct responses. Evidence against IOF is also presented, and a space-time aliasing artifact that can contaminate IOF displays is explored. Finally, DMP and IOF are separated, showing they can yield different results in different environments. Thus, it is concluded that (a) DMP and IOF are different, (b) DMP and not IOF is used for wayfinding, (c) moving observers do not usually decompose retinal flow, and (d) optical flow may be a mathematical fiction with no psychological reality.