In their book Think Like a Freak, economists Steven Levitt and Stephan Dubner state, "It has long been said that the three hardest words to say in the English language are I love you. We heartily disagree! For most people, it is much harder to say I don't know." They point to the following experiment as one of the many ways that we won't admit "I don't know":

Imagine you are asked to listen to a simple story and then answer a few questions about it. Here's the story: A little girl named Mary goes to the beach with her mother and brother. They drive there in a red car. At the beach they swim, eat some ice cream, play in the sand, and have sandwiches for lunch.

Now the questions:

1. What color was the car?
2. Did they have fish and chips for lunch?
3. Did they listen to music in the car?
4. Did they drink lemonade with lunch?

How'd you do? Let's compare your answers to those of a bunch of kindergarteners, who were given this quiz by researchers. Nearly all the children got the first two questions right ("red" and "no"). But the children did much worse with questions 3 and 4. Why? Those questions were unanswerable—there wasn't enough information given in the story. And yet a whopping 76 percent of the children answered these questions either yes or no.

Kids who try to bluff their way through a simple quiz like this are right on track for careers in business and politics, where almost no one ever admits to not knowing anything. [But it's a shame we can't humbly admit our ignorance], for until you can admit what you don't yet know, it's virtually impossible to learn what you need to.