A variant on the “Witch Ring” Illusion

 

Here’s another version of the illusion I’ve been working on with my colleague Priscilla Heard.  The bright V shaped zones imposed on the faces look like they are expanding sideways, especially near the sharp end of the Vs at the bottom.  But to the right an isolated bright zone shows that objectively the V tracks are quite static.  You may still see a bit of illusory lateral expansion even in this isolated set of tracks, but note that the top right corner of the track is quite static in relation to the corner of the movie.

It’s a version of the Witch Ring Illusion.   I posted about that back in 2011, noting a plan to take a look at it.  This year Priscilla and I published a paper about it in the journal Perception.