Also called reverse causation, reverse causality becomes a possibility when the “effect” of something could actually be its cause. For example, some studies have observed that diet soda drinkers are more likely to be obese than people who don’t drink diet soda. That’s led to speculation that artificial sweeteners in diet drinks may somehow cause obesity. Critics of that theory, however, have pointed out that people who are gaining weight may switch to diet drinks as a way to cut calories. Thus, they argue, the tie to obesity may be an example of reverse causality. Jodi Beggs has some funny examples of reverse causality on her blog, “Economists Do It with Models.”
