Note the paragraph that starts "Wundt's fundamental position..." Wundt's position, as related here by George Herbert Mead, is that modern people filter out illusions since "our reflection checks and criticises an apperception which otherwise would animate nature and its objects..." Our "reflective consciousness" acts to shut out such possible illusions before we even notice them. Children and primitive people, who are less influenced by such logical expectations, may therefore be more likely to see such illusions.
"Reflective consciousness" also makes it difficult for us to see the illusions that Winslow Homer saw and painted. The visual examples shown on this web site were selected partially because they are among the easiest to see.