*2.1. Subjects*

Different groups of 20 undergraduate students participated in each experiment described in the next sections. About 20% of the subjects had some basic knowledge of visual illusions, Gestalt psychology, and amodal completion, and the others were totally naive both to the stimuli presented

here and to the purpose of the experiments. They were about 50% male and female, and all had normal or corrected-to-normal vision.
