A Ponzo-like illusion left and right of fixation: a failed prediction.

Ponzo-like figures, with two parallel horizontal test lines superimposed on a pattern of converging background lines suggesting either a floor or a ceiling were presented in a tachistoscope unpredictably left or right of fixation, and the subjects had to compare the test lines as to length. The classical relative overestimation of the line closest to the apex of the background lines was obtained, but it was not stronger in the left visual field, as seemed to be predicted by at least two current generalizations concerning right hemisphere capacities: (a) that the right hemisphere is better at extracting spatial relations; (b) that its processing mode is more "holistic" and less "analytic" than that of the left hemisphere.