What to observe – On the right, black lines flank a red star. This red star sports a “neon glow” around it, so it looks a little like a red disk.
You will also observe changes – the outer lines disappear, or leave a gap, or are rotated. Also the colour settings vary.
What to do – By operating the check boxes, you can see the neon glow vanish when the black inducers disappear (‘autorun’ is automatically disabled). Any gap (due to shrinkage or rotation) destroys the illusion as well. The colourpicker helps you to assess the effect of colour. Any saturated colour works for the inner star.
Comment – While I sorted this phenomenon into the colour section, it works also with gray levels. The gap and rotation effects were described by Redies & Spillmann 1981.
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Tuijl HFJM van (1975) A new visual illusion: Neonlike color spreading and complementary color induction between subjective contours. Acta Psychologica 39:441–445
Redies C & Spillmann L (1981) The neon color effect in the Ehrenstein illusion. Perception 10:667–681
Redies C, Spillmann L & Kunz K (1984) Colored neon flanks and line gap enhancement. Vision Res 24:1301–1309
Bressan P, Mingolla E, Spillmann L & Watanabe T (1997) Neon color spreading: A review. Perception 26:1353–1366 [PDF]
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