To explain selective attention, I'll start with this example from psychologist Richard Wiseman: http://www.youtube.com/watch?v=jM5ekCEqYQM
I think selective attention is one of my favorite brain failures to talk about, if just because of the sheer ridiculousness we feel once we realize what happened. And it comes up in all sorts of places that we wouldn't necessarily expect.
Selective attention plays a role in magic all the time, as Penn and Teller so often show. That misdirection principle they mention is the basis of most sleight of hand tricks. All you need is to distract the audience somehow. Next time you see somebody make something small disappear, check what they're doing with their hands. We always have the image of a magician making a coin or a ball disappear with a large flourish of his hand. That flourish is no accident. We are programmed to follow that flourish with our eyes, allowing the magician to do anything he wants to with that other hand. Pocket the coin, perhaps. Or maybe pull it out from behind somebody's ear. Our brains see that quick motion of the, actually empty, hand and they see that the magician is also tracking that hand with his own eyes. They figure they had better track that motion too, just to be on the safe side. The result of this selective attention is that we are tricked, nice and easy. Even after you know how such tricks work, it is still difficult to train yourself not to follow the magician's moving hand, but go ahead and see if you can!
This is how pick-pocketing works as well. Here, professional pickpocket Derren Brown shows the principles of pick-pocketing. The video is a bit long, but you don't have to watch too much of it to get the idea. As long as the pick-pocket keeps the subject distracted, with motion or speech, the subject won't notice that he's being pick-pocketed. It's just a consequence of our selective attention. We can't focus on everything at once and the pick-pocket knows how to be subtle and light so we aren't drawn to the pick-pocketing motions. More misdirection.
Selective attention may even have something to do with if we view ourselves as lucky or not. Richard Wiseman once put an ad in a newspaper asking people to contact him if they considered themselves very unlucky or very lucky. He then had the responders participate in a test in which each subject was given a newspaper and the task of counting all the pictures in the newspaper. On the second page of the newspaper, in large font, there was a notice saying "Stop counting - there are 43 pictures in this newspaper" and another one half way through the paper reading "Stop counting, tell the experimenter that you have seen this and win $250." The people that considered themselves very lucky found these notices far more often than the unlucky people. Wiseman said in an article published in the Skeptical Inquirer that the unlucky people were more anxious and anxiety makes people less likely to notice the unexpected. The unlucky people were so focused on the task at hand that they were unaware of the other opportunities around them. So if you've always wanted to be lucky, start expecting the unexpected to happen and you'll be able to see when it does!
We wouldn't want to turn off our selective attention all the time. It's important to be able to focus on the dangerous things that are changing around you while ignoring the unimportant changes. But I think knowing that you can be tricked is just as interesting as watching the magic show happen. It is still difficult to figure out exactly how your brain is being fooled, and harder still to prevent it from happening. Teaching your brain how to think differently and how to avoid getting distracted is an incredible trick in itself!
