What to see
If you look around in the figure above you will notice the appearance and disappearance of black dots at the crossings, annoyingly at places where you’re not looking.
What to do
Do the streets or the squares influence the colour of the apparent disks?
There are 3 colour selectors (defaulting to gray, black, white). Try red squares: the illusory dots acquire a reddish tint…
The checkbox under “curve amplitude” introduces curvature into the streets. Most interestingly: that destroys the illusory dots.
Comments
Even though this figure looks similar to the Hermann Grid, it is markedly more vivid and should be named separately.
- 1985: First demonstrated by James R. Bergen at ARVO with a slightly weaker version
- 1994: Re-discovered by Bernd and Elke Lingelbach
- 1995: Demonstrated at the Tübingen ECVP meeting (Schrauf M, Lingelbach B, Lingelbach E & Wist ER. The Hermann grid and the scintillation effect. Perception 24: suppl, 88–89)
- 1997: Schrauf M, Lingelbach B & Wist E. The scintillating grid illusion. Vision Res 37:1033–1038
- 2001: Invoked to explain Florida’s election problems (“Count the black dots, recount to confirm…” ;-)
My sources suggested that it is probably caused by different mechanisms than those causing the Hermann-Grid effect. However, prompted by Sergey (thank you!) I introduced optional curvature here and the illusory dots vanish, just like in the Hermann Grid (curving). I interpret this as evidence that the Scintillating Grid and Hermann Grids will be traced to the same mechanisms, if currently largely mysterious.
Sources
Bergen JR (1985) Hermann’s grid: New and improved. Investigative Ophthalmology and Visual Science, 26 supplement, p280 [ARVO abstract]
Schrauf M, Lingelbach B, Lingelbach E & Wist ER (1995) The Hermann grid and the scintillation effect. Perception 24: suppl, 88–89
Schrauf M, Lingelbach B & Wist (1997) The scintillating grid illusion. Vision Res 37:1033–1038
VanRullen R, Dong T (2003) Attention and scintillation. Vision Res 43:2191–2196
Advice by Bernd Lingelbach gratefully acknowledged.