Target 1
Target 2
Stare at the red dot for 30 seconds. One circle is large, one is small.
Size Aftereffect Illusion
Explore the plasticity of size perception through retinal adaptation.
🧐 What do you see?▼
Stare at the red dot for 30 seconds. On the left is a LARGE circle, and on the right is a SMALL circle. When you switch to the test phase, two IDENTICAL circles appear.The one on the left will look smaller than the one on the right!
🧠 Why this works▼
This is the Size Aftereffect (a form of spatial frequency adaptation). Our visual system has 'channels' tuned to different spatial scales. By staring at a large object, you fatigue the 'low spatial frequency' (large scale) detectors in that specific area of your retina.
When you then view a medium-sized object, the remaining 'high frequency' (small scale) detectors have a stronger relative influence on your perception, making the object appear smaller than it actually is.
🧪 Try variations▼
- Change Intensity: Adjusting the intensity changes the scale of the adaptation circles. See how it affects the strength of the later comparison.
- Vary Fixation: If you move your eyes too much, the adaptation will be 'smeared' across the retina, weakening the effect.
❓ FAQ▼
Is this related to the Ebbinghaus illusion?
It's similar in result (perceived size change) but different in mechanism. Ebbinghaus is a simultaneous contrast illusion, while this is a temporal adaptation illusion.