You may have visited an amusement park fun house that utilized the research findings of perception psychologists: Balls appear to roll uphill and people appear to shrink before your eyes. The Ames room is a specially constructed room that, due to size and shape constancy, looks normal. Actually, the walls and windows are trapezoidal and one corner is much farther away from the observer than the other. When two people stand in the corners, one person looks small while the other appears a giant, and when a ball is rolled straight ahead, it appears to go uphill. Research indicates that the Ames room illusion can be explained by the lack of cues normally used in three-dimensional shape constancy (Dorward & Day, 1997).
