The demo of the 12 green blocks ... they all look exactly the same, even after knowing which one to look for.
And of course reminds me of this: http://discovermagazine.com/2012/jul-aug/06-humans-with-super-human-vision
And of course reminds me of this: http://discovermagazine.com/2012/jul-aug/06-humans-with-super-human-vision