Ghosts at the crossings: the Hermann grid

Rows:

Columns:

Cell size (px):

Gap size (px):

Horizontal curvature:

Vertical curvature:

Wiggle frequency:

Animate wiggle

Increase curvature to bend the grid lines. The classic Hermann grid (curvature 0) produces dark smudges at the intersections; bending the lines reduces the illusion.
Reference: Hermann, L. (1870). Eine Erscheinung simultanen Contrastes. Pflügers Archiv für die gesammte Physiologie, 3, 13–15. doi:10.1007/BF01855743. The wiggle slider follows Geier, J., Bernáth, L., Hudák, M., & Séra, L. (2008). Straightness as the main factor of the Hermann grid illusion. Perception, 37(5), 651–665. doi:10.1068/p5622

Demo for Lecture: Basic Neuro-cognitive Psychology.
Created by Z. Shi, msense Lab.