Shrinking neighbors: a quantitative examination of the 'shrinking building illusion'.

Buildings viewed through the window of another high building sometimes appear to shrink when we walk towards them. We refer to this phenomenon as the 'shrinking building illusion' and conducted a quantitative investigation to elucidate its underlying mechanisms. We created a virtual scenario to test the illusion using three-dimensional computer graphics. After viewing a movie in which the camera moves forward or backward in relation to the buildings, the participants adjusted the size of the test stimulus to the perceived size of the building in the movie. The results revealed that this illusion cannot be induced by two-dimensional factors alone, such as relative motion and size-contrast. Rather, the illusion appears to be strongly associated with self-motion.