The flashed face distortion effect is a pretty cool and rather creepy optical illusion. If you show two ordinary faces side by side with a gap in between them, then rapidly change the images and stare at a cross in the centre, the faces morph into grotesque versions of themselves.
The research was done by Matthew Thompson, and he has put out two videos; one with just women, and one with male and female celebrities. The effect is the same in both; converting pretty faces to ugly ones.
A really interesting illusion. Onwards!