The illusory perception of occluded space as empty depends on the occluded area.

Abstract

Some occluders evoke the compelling impression that the space behind them is empty. Stage magicians use this illusion of absence to produce objects out of thin air. The generic view principle predicts that the illusion of absence should increase with decreasing occluder size. We investigated this prediction in experiments where participants saw a partly occluded scene and the same scene without the occluder, revealing a piece of fruit. They then rated (1) how easy it felt to imagine that the fruit was hidden behind the occluder and (2) how likely they thought it was that the fruit was hidden behind the occluder. Both ratings increased with increasing occluder area. This shows that the illusion of absence increases with decreasing occluder area, as predicted by the generic view principle. These findings could provide a starting point for future studies aiming to understand and prevent road accidents involving obstructions of view.