Tomorrow, for the second consecutive month, will be a Friday the 13th.
Professor Phillips Stevens of the University of Buffalo, whose research includes topics such as cultural anthropology and religion, says this fear could have religious roots.
"The number 13 has been a taboo number for over probably two millennia now. It seems to originate in the story of the last supper of Jesus. There were 13 people at that table and the 13th was Judas, who betrayed Jesus, and the next day was the Crucifixion," Stevens explains.
The meal took place on a Thursday, and the Crucifixion was on a Friday, leading people to combine these ideas and create Friday the 13th.
While many call these fears superstitions, Stevens argues for the term "magical thinking."
Believing what is seen as superstitious isn't all bad either, and Stevens says. "Some of these so-called superstitions may be beneficial, like walking under a ladder, because they cause people to avoid risky situations."