ABSTRACT
The ghostly visual phenomena of illusory surfaces were discovered early in this century by Schumann (1904). Most curiously, they were almost entirely ignored for seventy years before Gaetano Kanizsa's beautiful examples, especially the famous Kanizsa Triangle (Fig. 19.1), (Kanizsa 1976; 1979). Why were they ignored for so long? Presumably because they did not fit any prevailing paradigm of vision. Whatever the reason, it is astonishing that they were not investigated - and seldom even seen! - even though Schumann's figure (Fig. 19.2) is given in the most widely-read excellent textbook of psychology of the 1940s and 1950s, Robert Woodworth's Experimental Psychology (1938). There it is on page 637. I must have seen this as an undergraduate yet failed to spot its significance. It is to Kanizsa's immense credit that he saw where others were blind. With his evocative examples he made us see also. Perhaps it is no accident that Gaetano Kanizsa was a painter, and in his science, a phenomenalist.
