Thirteen: The Private History of a Curse

This is not going to be an episode where we state the obvious. Nobody listening to Skeptoid thinks it's unlucky to see a black cat or walk under a ladder, and nobody here thinks 13 is an unlucky number. There are no such things as lucky or unlucky numbers, so we're not going to waste time or intelligence "debunking" specific superstitious beliefs. Rather, this will be the history of how and why 13 came to be considered unlucky in many Western countries. That's the interesting part, and it's a lesson which extends to all countries and all beliefs in luck and curses and hexes. But perhaps even most interesting of all are the reasons that you don't need to be superstitious to still feel a moment of discomfort whenever you encounter that allegedly-unluckiest of all integers: 13.

Let it not be claimed that superstitious beliefs do not impact our daily lives. We're all familiar with the way many buildings skip numbering their 13th floor. Many omit room 13 as well. Some airliners don't number their 13th row. We see things like this all over the place.

Most sources attribute the origin of 13 as an unlucky number — at least to Christians — to the story that there were 13 people at Jesus' Last Supper. Tradition holds that Judas, who betrayed Jesus, was the last to arrive and was thus the warmer of the 13th seat (though nothing in the Bible actually says this). Various authors began making this association in or around the 17th century — there doesn't seem to be any clearly known origin for this, but most sources agree it's a fairly modern interpretation. But note how similar it is to its Norse counterpart. Legend tells of 12 gods having dinner at Odin's table, when in walked the uninvited 13th guest, the mischievous Loki. Loki soon schemed for Hoder, who was blind, to shoot an arrow at Balder the Beautiful, killing him. This story dates from around 1000 CE, give or take a century or two, but there's little evidence that it had much influence on Christian beliefs at the time. Nevertheless, both likely underpin the modern superstition that it's unlucky to be the 13th dinner guest.

One hard data point supporting a later origin for the Western distrust of 13 is attributed to a 1910 translation of the Babylonian Code of Hammurabi by an L.W. King, in which one of the laws was omitted. The laws in the Code of Hammurabi aren't numbered, but the omitted one was the 13th, and had to do with damages from a sale made by a person since deceased. There is no reason to suspect King's omission was anything other than accidental, but it doubtless confirmed in someone's mind that things that were the 13th in a series were to be avoided.

And this leads us to a couple more points that were at the time — and to some degree, still are today — rooted in the public consciousness. We have about 13 moon cycles per year, and the symbol of the moon has long been a female symbol in Western cultures. 13 times a year, according to Leviticus, women are "unclean" due to their menstrual cycle. More than one scholar has linked unclean, sinful women to the witches who fly on their broomsticks during each of the year's 13 full moons. Obviously this connection is heavy with obsolete cultural baggage; but women's physiological link to the number 13 is a real one and their place as second-class citizens in all the Abrahamic religions is undeniable. To many members of the class of white men who defined and codified societal norms over the past few millennia, 13 had profound negative connotations at a deep fundamental level. We can't easily quantify how much influence that this may have had on today's image of 13 as an unfortunate number, but whatever that amount is, it's non-zero.

Another interesting possibility that's been suggested by multiple scholars on the subject is that 13 comes after 12, and 12 is a number that has a lot of positive connotations. 12 months in a year, 12 eggs in a dozen, 12 numbers on a clock, 12 apostles of Jesus, 12 inches in a foot, 12 signs of the Zodiac, 12 tribes of Israel, 12 days of Christmas, 12 gods of the pantheon, 12 members in a jury, 12 pitches in musical scale... it goes on and on. 13, by following right on 12's heels, charges in and screws everything up. Adding one more to any of those things ruins it. It's not hard to imagine that throughout history, many people wanted 12 of something for some purpose related to any of the foregoing, and 13 would always be an undesirable (or "wrong") number.

Our brains are wired to think anecdotally and to assign early significance to the first associations our brains make. Thus, according to our healthy brain's normal function, when we see 12 of some quantity and 13 of another, we're likely to have a flash of positivity about the 12 and negativity about the 13. This tendency of our brains to automatically spot patterns is called apophenia, and it explains why you — as a healthy person with normal function and minimal tendency toward superstitions — should still be expected to feel a slight discomfort upon seeing a 13. Intellectually, we all know there's nothing wrong with 13, but such a higher-level analysis as that comes slower than the fast-match provided by apophenia. If you get handed, say, ticket #13 at an event, your normal, healthy reaction should be to feel a split second of negativity — perhaps surprise or disappointment, followed very quickly by a moment of logical relief, and maybe even laugh to yourself over your initial reaction. This is neurology, and it doesn't mean you're superstitious. It means your human skull is stuffed with a human brain.

As evidence of this, I ask you to try a little experiment next time you're in an elevator and notice there's no button for the 13th floor. Seeing that series go directly from 12 to 14, did you not feel a tiny flash of reassurance, perhaps safety or a sense of being protected? What just happened is that your apophenia did not kick in — as it would have in an elevator with a complete set of buttons — and thus you were spared that little useless, ridiculous pattern-match that flashes you with discomfort upon the appearance of a 13. Superstitious people might consciously appreciate the lack of a 13th floor; and now we can see that non-superstitious people also derive at least a tiny amount of actual relief from it. Plus, it gives us something fun to mock as we ride the elevator. For me, when I ride such an elevator and think of all these fascinating implications, it's a wonderful little real-world science demonstration.

There is another interesting side-effect of this apophenia-induced validation of 13 as a bad number, and that's the way some people try to rationalize it by seeking real-world proofs that 13 is, in fact, somehow bad. A famous example of this came in 2005, when the Telegraph newspaper ran an article that talked about the UK's National Lottery. It talked all about it: what the odds are, what the top payouts have been and how many prizes have been won, how the taxes work, what winners tend to do with their money. In one paragraph about halfway through, it mentioned that the luckiest numbers had been 38, 25, and 31, having been drawn 182, 175, and 166 times respectively; while the unluckiest numbers had been 13, 41, and 16, having been drawn only 120, 126, and 127 times. What headline did the editors give this comprehensive article? Was it "All About the Lottery"? No, it was "Coincidence? 13 really is the unlucky number". (As a comical footnote for Skeptoid listeners, who are presumably of a logical mindset, this lottery article appeared in the paper's "Personal Finance" section.)

But we can also look at this pragmatically. How many lotteries are there in the world? A thousand? Ten thousand? Are 13 and 38 the luckiest and unluckiest numbers in all of them? Of course not. But some fraction of all the world's lotteries have 13 as the unluckiest number. But the corollary is that an approximately equal number of lotteries have 13 as the luckiest number. This result printed in the Telegraph was cherry picked data.

Following this same cherry picking methodology, I could look at a database of traffic accidents and see what's the most dangerous street in every city. Inevitably, for some cities this will be 13th Avenue, just as it will be 12th Avenue for others and Martin Luther King Boulevard for others. Then all I need to do is publish a detailed analysis of the traffic accidents in that one (carefully chosen) city, and prove that 13th Avenue is the most dangerous street in Los Angeles (or whatever city it is), and thus confirm that 13 is an unlucky number. If you look carefully at most claims where 13 turns up unlucky, you'll probably find that it employs this same type of cherry picking.

The irony of all these attempts to find validations for the curse of the number 13 is that their net effect tends to be just the opposite. The fact that some people take superstitions at least somewhat seriously actually does make people safer, counterintuitive though that may sound. For example, some people don't go out on Friday the 13th, and fewer people on the roads has resulted in fewer traffic accidents. There are also fewer fires and thefts reported. This was according to a 2008 study by the Dutch Centre for Insurance Statistics, which found only 7,500 traffic accidents on average on a Friday the 13th, compared to 7,800 on other Fridays — a drop of about 4%. 4% is big if you think about the number of people needed to stay indoors because of the number 13.

Popular histories of the number 13 often include a mention of the Thirteen Club, a tongue-in-cheek philanthropic association of notable rationalists at the College of William & Mary, founded around 1880. Their 400-some members eventually included five US presidents. Tradition holds that they would get together over dinner in New York City, 13 to a table, and challenge the fates to see if one of them would die within a month, according to the popular version of the curse of 13 at a table. None ever did. Their purpose was to hold humanity to a higher standard, one not crippled by adherence to faith in the irrational. But a lack of anything interesting happening is a poor excuse for a club to endure, so the Thirteen Club fizzled away by around 1920. This leaves us with truly the most interesting factoid about 13 as a cursed quantity, and that's that I managed to get through this entire episode without once mentioning triskaidekaphobia.

By Brian Dunning
Follow @BrianDunning