HORIZONTAL AND VERTICAL DISTANCE PERCEPTION - THE DISCORDED-ORIENTATION THEORY

We sought the conditions where the horizontal-vertical illusion (HVI) takes place outdoors in an open field. Longitudinal distance from a su bject to a building wall was adjusted to appear equal to the vertical or horizontal distance on the wall. To examine validity of previous th eories (physiology, frame, depth, and gravity theories), boundary of v isual field (ellipse and circle), bodily orientation (upright and lyin g), and orientation of visual objects (normal, 90 degrees-tilted, and inverse) were manipulated in eight experiments. These three independen t variables affected the HVI effects, but their effects were not expla ined by the previous theories. We therefore proposed a model on the ba sis of discord among the retinal, visual, and gravitational orientatio ns. We also found that longitudinal distance was adjusted as being con sistently larger than the standard distance. This result was explained by the reduction of cues to distance and the HVI effect.