Illusions

In Chapter 4 of our text, the authors note that illusory contours “have real perceptual presence, although the observer seems to have the feeling that they are not really ‘real’” (110). They note that this gap in the research literature should be further investigated.

It seems to me that in the context of visual illusions such as the one printed in the text, the effects of past experience could logically explain this concept. If people have seen similar illusions in the past, then they have the feeling that the contours are not “real” because they are aware that they are viewing an illusion and have prior experience with similar perceptual experiences. Of course, this explanation would not hold if someone naïve to illusions also experienced the doubt of the contours being “real.”

I’m just curious to see if anyone has any other possible explanations for this, or just any ideas about the phenomena. If so, is there a way to test these hypotheses?