Or, "Just how stupid people really are"
Psychology is an odd science. In the quest for knowledge about the human mind, some truly bizarre things have been done. This node is an ongoing project to catalogue them; all are 100% true. Please add any you've heard of, or softlink them. Here's a few for starters.
In one notable experiment, an experimenter approaches subjects in the street and starts a conversation. In the middle of the conversation, some accomplices posing as removal men move a large object between the subject and the experimenter, so the subject can't see the experimenter. The experimenter then quickly changes places with an entirely different person, who has no striking differences from the experimenter, like say being a foot taller or a different sex. Most subjects either don't notice that they are talking to a different person when the object is moved on, or don't let on that anything has changed. Apparently it shows just how little attention most people pay to things, and how our expectations can stop us from perceiving things that are completely out of context... which leads us to another experiment...
To demonstrate a point about selective attention, subjects are shown a video recording of a basketball game. There are two teams, one dressed in black, the other in white. Subjects are asked to count the number of passes the white team make. They're usually not too bad at this; it's not the hardest task in the world. However, most subjects don't see the guy in the Gorilla suit who walks across the court half-way through... I know it sounds crazy, but I've seen the video and done it myself; because you're keeping track of people in white, you ignore the black team, and also the black gorilla. The subjects are then shown the video again, and the experimenter points out the gorilla; he's clearly visible, he just saunters nonchalantly across the court without a care in the world, yet no-one notices him first time round.
In another experiment, subjects were given a new questionnaire to assess their personality. They were asked to fill it in and return it, and were given a brief summary of their personality type afterwards. They were then asked to rate how accurate the summary was regarding their personality. The test was apparently very accurate; the subjects gave an average mark of 4.3 out of a possible 5, and were all happy with the results. However, the individual assesments that had been given to them were, in fact, all exactly the same. The experimenter had made one assesment by taking phrases from newsstand astrology books such as "you are often insecure inside but show strength and determination externally", and "you are sometimes unsure about which course of action to take, but eventually come to a decision", and given a copy of it to every single participant. It just goes to show the true worthlessness of astrology books, and the never-ending gullibility of the human race. And that you should never trust Psychologists.