I never understood why people are so superstitious about Friday the 13th. So I did a little digging into the history of this particular belief. It turns out that Friday has long been considered an unlucky day, which is interesting because in the modern professional world, Fridays are often perceived in a positive light—they indicate the end of the work week and the beginning of the weekend. In addition, the number 13 is widely considered unlucky; this is related to the number 12 being viewed as natural or divine (12 months of the year, 12 Apostles of Jesus, 12 signs of the Zodiac, etc). The number 13 must be unnatural then or in violation of the sacred.
Thus, if you combine the unlucky day of the week with the unlucky number 13, you have a bad luck combo. Indeed, according to Christian tradition, Jesus Christ was crucified on a Friday and Judas, the disciple who betrayed Jesus, is believed to have been the thirteenth guest at the Last Supper.
This is all fascinating but what interests me is why people in the modern world still hold on to such superstitions. There is research that answers this question.
Superstitions help people make sense of the world, especially when we feel we lack a sense of control. Humans want to perceive the world as orderly and predictable. We want it to feel controlled, not chaotic and random. Of course, we cannot always control outcomes in the world. Thus, we often invest in beliefs that suggest there is some external agent or force (e.g., God) that is in control of the world. A good example is when people attribute outcomes that do not make a lot of sense to them (e.g., not getting that promotion at work you think you deserved) to fate by saying something such as “I guess it was not meant to be.”