I used to teach research methods and statistics at the University of Denver. The holy grail of research is to prove a cause and effect relationship: x causes y. The only way to do that is with the experimental method — manipulating the independent variable. But it’s often difficult to use the experimental method in the social sciences. (Let’s see — we’ll send 100 randomly selected people to jail for 20 years to see what the effects are. Try getting that past your ethics committee.) So, in the social sciences, our research often shows correlation rather than causality. If you think you’ve shown x causes y, you also have to ask the question: could y cause x? In other words did we get it backwards?
I tried this with moods a few years ago. I always thought that being in a good mood (independent variable x) caused me to smile (dependent variable y). So, x causes y, right? I decided to try the opposite as well to see if I could improve my mood by smiling. Lo and behold… I could. So, my mood — to some extent, at least — is my choice. Smiling helps me improve my mood when I’ve had bad day and may even help my athletic performance. It also drives my friends crazy. (What’s he smiling about?) So next time you’re feeling down, try smiling. It may just turn your day around.