His illusions here were based on a 2000 paper titled "A new illusion demonstrates long-range processing" (
https://www.sciencedirect.com/science/article/pii/S004269890...) That paper showed that there is a global mechanism for orientation averaging. I've always been fascinated with the idea of using illusions to reverse engineer our visual system and this is a really good example of that. The paper is a really accessible read and the rest of Kitaoka's website is a treat to browse:
http://www.psy.ritsumei.ac.jp/~akitaoka/