A nice and geeky xkcd strip for this year's April Fools day talking about perception bias in the form of umwelt.
The alt text reads:
Umwelt is the idea that because their senses pick up on different things, different animals in the same ecosystem actually live in very different worlds. Everything about you shapes the world you inhabit--from your ideology to your glasses prescription to your browser window size.
The strips seem to be generated based on what browser the user is using, as well as the size of the window and the IP address.
As usual, Randall Munroe proves to be awesome.