Tilted by the surround: the tilt illusion

Center orientation (°):

Surround orientation (°):

Center disk size (px):

Surround disk size (px):

Grating frequency:

Grating contrast:

Tip: The center grating's perceived orientation is influenced by the surround. Try setting center to 0° and varying the surround to see the tilt illusion effect.
Reference: Gibson, J. J., & Radner, M. (1937). Adaptation, after-effect and contrast in the perception of tilted lines. I. Quantitative studies. Journal of Experimental Psychology, 20(5), 453–467. doi:10.1037/h0059826

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