The global figural characteristics in the Zöllner illusion.

The Zöllner illusion has been accounted for in terms of local interactions between the vertical lines and the crossing segments. Recently, however, some evidence supporting the importance of global figural characteristics--ie of figural elements that are not directly interacting with the test lines--in the occurrence of orientation illusions has been reported. Three experiments have been conducted with parts of the Zöllner figure to test whether this illusion is affected by the global figural characteristics. The results indicate that, similarly to what has been observed for other orientation illusions, the Zöllner illusion depends on both local and global characteristics of the stimulus configuration. In addition, results suggest a similar weight for both these figural characteristics in determining the occurrence of the illusory effect. Finally, relations among different orientation illusions are also discussed.