VISUAL ORIENTATION ILLUSION FOLLOWING JUDGMENTS WITH A TILTED VISUAL FIELD

Asch and Witkin showed that when an observer adjusted a bar on the far wall of a miniature room tilted at 22°laterally, the apparent vertical of the bar was displaced about 10°-14°in the direction of room tilt1. We report here an experiment which shows that earlier exposure to a similarly tilted room produces the same direction of change in apparent verticality when a luminous bar is adjusted in darkness. This experiment included appropriate controls for the occurrence of a spatial after-effect2,3, and so the data suggest that illusory effects persist after the conditions inducing them are removed. © 1969 Nature Publishing Group.