On Coincidence and Belief

I couldn’t help but respond to Peter Cawdron’s insightful post on astrology. It got me thinking about my encounters with astrology believers. And, lazy person that I am, I decided to turn my comment into a long overdue blog post.

I once read about a study done on astrology believers. If someone successfully guesses the color of a playing card (red or black) 50% of the time, astrology believers are more likely to conclude that such a high percentage of accurate guessing can’t be coincidental, and some form of telepathy (or something more mundane, like cheating) must be at play. (Of course, we all know that 50% is the expected outcome from mere guessing.) In conversations I’ve had with astrology believers, they frequently punctuate their discussion with, “I KNEW IT!” whenever they encounter something — anything — that reinforces their beliefs, no matter how coincidental.

As a consequence of this manner of thinking, there is a movement among some astrology believers to change the name of the sign of Cancer to something else, since fully one out of twelve cancer patients are born under the sign of Cancer, which can’t be mere coincidence, they are convinced. How does mere nomenclature influence the distribution of cancer diagnoses among the signs of the Zodiac? Who cares? Renaming the sign makes the problem go away, case closed. By renaming the Cancer sign to something else, the correlation ceases to apply, so there’s no reinforcement making the coincidental stand out. It’s a mind trick that relies on suppressing the mere appearance of correlation without actually affecting anything that makes a difference.

However, the plan might backfire due to their shortsighted choice for Cancer’s new name. What is the new name they’ve selected for Cancer? They’ve selected FLESH EATING BACTERIA.

I know, right?