I'm sure everybody in here knows about optical illusions, but you might not know that these aren't the only systematic ways to fool your brain. There are grammatical illusions ( "More people have written about this than I have." ) and even moral illusions, like the one outlined in this experiment:
You're standing on a bridge and taking in the scenery, when you see the driver of a street car suffer a heart attack and die. The trolley is racing down hill, and no one is controlling the brake. Down the hill, five people are standing on the tracks, unaware of the train coming at them. Next to you is a fat man, looking in the other direction, standing near the end of the bridge. Will you push him over the ledge, knowing that his weight will stop the street car, killing him in the process, and saving the five people below?
Everybody says no, they won't; it's repulsive to think about. But now change the question in an insignificant way: Will you pull a lever, opening a trap door below the fat man, which will dump him onto the tracks, killing him, stopping the train, and saving five other people? Suddenly, things aren't so clear, and without the salient moral reaction, people think rationally, and most of them suppose it's better to save four "net" lives.
But my point is that every man in this forum needs to lose some weight, because we're the braking system of last resort for runaway trains everywhere! They're even building in trap doors to catch us. So, get out and put some miles on the bike, but in the mean time, watch yourselves around bridges and street car tracks!