The Ebbinghaus illusion with small inducers appears larger on the right side

The effects of left and right alignment on the Ebbinghaus illusion were investigated in three experiments. In Experiment 1, the Ebbinghaus illusion was presented on the left or right side, and the points of subjective equality (PSE) were measured. Only the central disk of the figure with small inducers was perceived larger when it was positioned on the right side rather than on the left. In Experiments 2 and 3, left, right, and central placement were used to determine if the results of Experiment 1 were caused by a decrease of the illusion on the left side or an increase of the illusion on the right side. There was no difference in the illusion effect between the left and the center; however, the illusion effect increased when the figure was presented on the right side. These results suggest that a hemispheric asymmetry for global and local spatial attention influences the laterality of the Ebbinghaus illusion.