What Is Behind Distortions of Reality?

• Position: Research on human's visual perception - Brief Article

Magnetic anomalies emanating from the Bermuda Triangle, antigravitational forces caused by UFOs, and an "ineffable, natural phenomenon that cannot be described or explained" are among the supernatural explanations of the house in Santa Cruz, Calif., known as the "Mystery Spot." It is one of more than a dozen places in the nation which create visual illusions so compelling that people reach for metaphysical reasons to explain their experiences.

This is a house where balls roll uphill, chairs sit on walls, and people lean over so far they can't see their shoes, yet they don't fall down. Nineteenth-century psychologists had theories to explain illusions like this, but the less-than-compelling explanations left considerable room for mystery. Now, psychologists from the University of California, Berkeley, have generated a new theory based on experimental data that goes much further in explaining all the effects of these phenomena.

Central to their thesis is the human need to establish horizontal and vertical orientations and the extent to which people will take their cues from the immediate context if they can't see the Earth's horizon. "All the visual illusions in the Mystery House derive from the fact that the house is tilted," notes William Prinzmetal, adjunct associate professor of psychology, who conducted the studies with psychology professor Arthur Shimamura. "You know the house is tilted, but you don't know how much. Everything is tilted. You can't look outside and get a horizon, so you think that what you see is right. It's very compelling." Prinzmetal, an expert on perception, has been to the Mystery Spot a dozen times. Although he has studied these illusions, he indicates that his visual perceptions still are distorted when he goes into the house, tilted at a 20 [degrees] angle from the ground.

It doesn't take a scientist to know that cockeyed rooms affect perception. If floors are slanted, for instance, people will hang pictures on a slant. What has not been demonstrated is that, when the perceiver's body also is tilted, the distorting impact on vision is greatly magnified--up to two or three times the effect of slanting the visual field alone. "In the tilted condition, you are much more affected by the immediate visual context," explains Prinzmetal, who has tested dozens of...