Add Yahoo as a preferred source to see more of our stories on Google. Hand flattening peanut butter cookie dough with fork - Carey Jaman/Shutterstock It's pretty easy to identify the peanut butter ...

peanut butter cookies on a wire rack and a glass of milk - Mizina/Getty Images Answers to questions like, "Why is the sky blue?" tend to elicit a knee-jerk response like, "That's just the way it is" — ...