4 ms·The `footsteps' illusion in CSS1 points by bwasti 9y agobwasti 9y agopaper: https://quote.ucsd.edu/anstislab/files/2012/11/2001-Footsteps-and-inchworms.pdf https://quote.ucsd.edu/anstislab/files/2012/11/2001-Footstep... (2000)