You find a four-leaf clover, but when bending down to pick it up, a black cat crosses your path and you’re back to break-even on the luck front. In our culture, other traditional signs of good fortune have been number 7, horseshoes, and a rabbit’s foot. Meanwhile, misfortune is said to await those who break mirrors, walk under a ladder, or open an umbrella indoors.

Of course, these vary by culture. The Chinese see 8 as lucky and the swastika was considered a symbol of good fortune in Sanskrit-speaking lands being coopted by the Nazis in an extreme act of cultural appropriation.

While most persons see superstitions as quaint, others take them more seriously and are convinced they are behind good or bad luck. When persons do this, their actions can accurately be ascribed to post hoc reasoning and subjective validation.

But there may be a scientific explanation for why humans fall prey to such beliefs. According to Dr. Steven Novella of the New England Skeptical Society, superstitions arise from a need to feel in control. The illusion of control can be either primary or secondary. The former occurs when the person undertakes a physical action he or she hopes will lead to positive results, such as clutching a favorite stuffed animal, a pitcher pointedly avoiding stepping on the foul line, or an employee wearing red to every job evaluation. Secondary control refers to trying to access an external force, be it astrology, a deity, or a cosmic energy, and seeking to benefit from it. Novella writes that humans have developed overactive detection sensors and sometimes assume that events result from design instead of chance. This leads them to attempt to control or contact the entity responsible.

But overactive sensory detection may also carry an evolutionary advantage. Noticing an authentic pattern, such as cobra-strike victims succumbing to a painful death, would be a significant survival tool. Meanwhile, the detector misfiring and causing us to freak out over a harmless spider or to think that a lucky fedora will help our team win will have little detrimental effect. This would push the brain’s pattern-recognition ability into overdrive and cause it to error on the side of caution.

The British Journal of Psychology referenced a study in which subjects gauged the relationship between pressing a button and a light coming on. There was no connection between the two; the illuminations were randomly generated. But most subjects considered the relationship to be at least moderately casual, even though this was an illusion. Crucially, the magnitude of this illusion increased in a pattern consistent with how superstitious the person was. Their level of superstition had been determined in pre-study questionnaire.   

In another finding cited by Science, participants who lacked control of their situation were more likely to perceive a variety of illusory patterns, such as seeing images in noise, forming mistaken correlations about the stock market, detecting conspiracies and, yes, developing superstitions.  

Then in “Evolution of Superstitious Behavior,” by Kevin Foster and Hanna Kokko, the authors assert that superstitions arise because of a misunderstanding of cause and effect. But they also posit there may be times when natural selection adopts strategies that lead to frequent errors in assessment, as long as the correct responses help with survival and adaptation. In other words, the baseless fear of a black cat crossing your path is the tradeoff for your fright at a cobra doing the same.