Old Maps and the Watercolor Illusion: Cartography, Vision Science and Figure-Ground Segregation Principles

Abstract

Long-range color spreading is studied in two experiments in which a purple contour is flanked by an orange contour. The color faintly but uniformly fills in the surface from the orange contour inducing a strong figural effect and is therefore known as the Watercolor illusion. The figural effect of the watercolor illusion is compared with classical Gestalt factors (past experience, similarity and symmetry). The results of the experiments reveal a more effective role of the watercolor illusion in form perception and in figure-ground segregation than the one of the past experience principle and, in addition, corroborate the perceptual effects in distinguishing and demarcating geographical regions obtained by early cartography using the outline-color technique. The results are explained in terms of Grossberg’s FACADE neural model of biological vision.