This optical illusion is a variation on the previous optical illusion with the gray ghosts appearing in the intersections of the black grid.

We still have a black grid here, but now the lines are gray and there are white circles in the intersections. Have a look and try to count all of the black dots you see.

Step 1: What black dots?

The black dots you see don't really exist. Whenever you try and look at one directly, it will disappear. I don't know why this happens as I haven't found a good explanation for it. Feel free to let me know if you have any insight into the comments.

The goal of this Instructable is to show you how to quickly recreate such a grid with a graphics program. You can then make some variations of your own.

To start with we'll want a gray background. Lock this or put it on another layer and then start making your building block.
<p>This is lateral inhibition. </p><p>&quot;In neurobiology, <strong>lateral inhibition</strong> is the capacity of an excited neuron to reduce the activity of its neighbors. <strong>Lateral inhibition</strong> disables the spreading of action potentials from excited neurons to neighboring neurons in the <strong>lateral</strong> direction.&quot; this is happening in your eye.. </p>
<a rel="nofollow" href="http://en.wikipedia.org/wiki/Grid_illusion">http://en.wikipedia.org/wiki/Grid_illusion</a><br/>
these are always fun. <br/>for further enrichment via a tangible, print-source, check out the book &quot;The Mind's Past&quot; by Michael S. Gazzaniga. That's right, pimping a real live book on the internet! It can be read in parts online on google books-HERE-&gt; <a rel="nofollow" href="http://books.google.com/books?id=pbbmsc-jZa8C&amp;dq=the+mind%27s+past&amp;printsec=frontcover&amp;source=bl&amp;ots=qbr3xN9hzI&amp;sig=cVNpfipbMCaKvLD0u1Mqtyg-nLs&amp;hl=en&amp;ei=XvwCSo_gOp3CmQe3mKHtBA&amp;sa=X&amp;oi=book_result&amp;ct=result&amp;resnum=3#PPP1,M1">http://books.google.com/books?id=pbbmsc-jZa8C&amp;dq=the+mind%27s+past&amp;printsec=frontcover&amp;source=bl&amp;ots=qbr3xN9hzI&amp;sig=cVNpfipbMCaKvLD0u1Mqtyg-nLs&amp;hl=en&amp;ei=XvwCSo_gOp3CmQe3mKHtBA&amp;sa=X&amp;oi=book_result&amp;ct=result&amp;resnum=3#PPP1,M1</a><br/> <br/>Chapter 4 is particularly relevant to this instructable.<br/>Thanks for the heads up on the html<br/>
This is easy to create with a few lines of script using the free software <a rel="nofollow" href="http://www.contextfreeart.org/gallery/view.php?id=1771">Context Free Art</a><br/>
This is really weird, but very interesting<a rel="nofollow" href="http://www.sevensoftware.be/">,</a> thanks!<br/>
Haha! I first thought the grid has programed flashing dots until I realize I was actually chasing them... lol
It's pretty complicated to explain. I'm a psych PHD, and I don't entirely understand it, even after reading a lot just now and having taken perception courses (I don't do vision stuff at all, though, of course). Basically, all of the theories out there right now have one thing in common, though - they all agree that this is an illusion caused by one or more of various systems our nervous system uses to try and detect edges better. Edges are immensely important to people, because they help us perceive the shape of an object, and the boundaries of an object, so we have evolved a visual system that is not only good at seeing them, but actually goes out of its way to make the edges MORE visible than they are in real life. This enhancement goes too far, sometimes, though, causing us to see false edges, like in the illusion. Then it's downhill from there in terms of details. I always learned it was opponent cells, but meh.
you probably already knew this, but this is called a hermann grid
Nice. Explains a lot of artistic magic / science; like when looking back and forth from the eyes for a few seconds and then to the mouth on the Mona Lisa.
OMG!!!! Where did they come from? Aliens?
25. very fun to look at, but not directly at. thanks for the diversion.
I dont see the red/green one, probably my bad eye.<br/>I tryed to make a gradient version, you clearly see the dot are darker on top.<br/>I also tryed to put another image in the square, also seem to work.<br/>I also noticed that the smaller the grid is, the better you see the dot. for exemple, make a really huge version and you barely see the dot.<br/><br/>Here is the explaination wikipedia give:<br/><a rel="nofollow" href="http://en.wikipedia.org/wiki/Grid_illusion">http://en.wikipedia.org/wiki/Grid_illusion</a><br/>
Found this to be quiet interesting.
If I focus my eyes exclusively on one of the small squares in the grid, I do not see a black dot. So in my mind it is when we look at the entire grid that we see the black dots (if grid squares are red we see red dots etc.). Good optical illusion!

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