"Birds of a feather flock together" "opposites attract"
In chapter one, the book discusses the many mental traps that students, and even researchers can fall into from time to time. The two common sayings above, taken from our textbook, are a great example of one of these issues. We like to believe that we are always, or nearly always correct in our thinking. This is why we can see two similar people walking down the street and say, "birds of a feather flock together," and then five minutes later see a seemingly mismatched couple and say, "opposites attract" and we don't even notice the complete contradiction in our logic, until it is pointed out to us.
My own example of this happened around Christmastime, when my family was separating out the presents, and the younger kids all ran to find which of theirs was the biggest. "Bigger is better." However, when my mom received a necklace in a small box, she said, "The best things come in small packages." We say things like this all of the time, without realizing the complete contradiction that is present.