On Friday the 13th, and vast numbers of people across the world avoid going about their usual business because they fear this day will bring them "bad luck." In this Spotlight feature, we examine the psychological mechanisms behind superstitious thinking.

Speaking of business, not only do airlines and airports routinely skip a 13th aisle or the 13th gate, but more than 80% of high-rise buildings all over the world lack a 13th floor. Also, some hotels and hospitals often choose not to have a room with the number 13.

Billions of people in the United States and across the world are superstitious. A quarter of adults in the US consider themselves to be so, and recent trends reveal that younger people are more superstitious than older adults. In fact, 70% of US students rely on good luck charms for better academic performance.

Millions of people in China think the color red or the number 8 will bring them wealth and happiness, while a study of consumers in Taiwan showed that shoppers tend to pay more money for fewer items in a package as long as the number of items in the package represents a "luckier" number

Most of us know that these beliefs are irrational, but we still abide by them. Why do we do it? Do superstitions fulfill an important psychological role, and if so, what is it? What are some of the mechanisms that explain these irrational beliefs, and how do superstitions affect our mental well-being?

Why do we believe the unbelievable?

The fascinating thing about superstitions is that we often believe in them despite knowing, on some level, that they can't be true. Why do we do this?

Jane Risen, a professor of behavioral science at the University of Chicago Booth in Illinois and a member of the American Psychological Society, has used the so-called dual process model of cognition to explain our belief in superstitions.

According to Risen (and other renowned authors, such as Daniel Kahneman), humans can think both "fast" and "slow." The former mode of thinking is snappy and intuitive, while the latter is more rational, and its main job is to override the intuitive judgment when it finds errors.

The dual thinking model is an established one, but in the case of superstitions, Risen suggests that the model should undergo refinements. The researcher notes that error detection does not automatically involve error correction. In other words, people can realize that their belief is wrong but still act on it.

The "thinking fast and slow" model "must allow for the possibility that people can recognize—in the moment—that their belief does not make sense, but act on it nevertheless," writes the author. "People can detect an error, but choose not to correct it, a process I refer to as acquiescence," she continues.

But superstitions are not merely a manifestation of our flawed cognition. Sometimes superstitions offer a host of benefits.

How superstitions may relieve anxiety

Sometimes superstitions can have a soothing effect, relieving anxiety about the unknown and giving people a sense of control over their lives. This may also be the reason why superstitions have survived for so long—people have passed them on from generation to generation.

As an article appearing in the International Journal of Psychology and Behavioral Sciences states, "Superstition has its roots in our species' youth when our ancestors could not understand the forces and whims of [the] natural world. Survival of our ancestors was threatened by predation or other natural forces."

As a result, superstitions have "evolved" to produce "a false sense of having control over outer conditions," and reduce anxiety. This is also why superstitions are "prevalent in conditions of absence of confidence, insecurity, fear, and threat."

A Medical News Today reader, who describes their parent's various superstitions, echoes the same sentiment. "My mum has tons of superstitions," they say. "[She] can't walk under a ladder, can't put new shoes on the table (even in their box), can't break a mirror, can't give a purse without money in it, [has] to throw a pinch of salt over her left shoulder if she spills some."

"I think some of these are just common sense comments, such as don't break a mirror or you might cut yourself because the shards are sharp, that have grown into something more. But they transform into this set of rules to live by, often for no apparent reason," the reader continues.

"I think life is a series of random coincidences and can't be shaped by these strange little habits, but I guess it's reassuring to believe you have some control over it—especially when there's so much about our lives and society that we can't change."

—An MNT reader

"Life is pretty scary sometimes," they add, "so [...] people [do] whatever they can to try to avoid hidden dangers."

Superstitions may improve performance

Furthermore, by alleviating anxiety, superstitions may objectively improve performance. Stuart Vyse, author of Believing in Magic: The Psychology of Superstition and former professor of psychology at Connecticut College, explains in an interview for the British Psychological Society:

"There is evidence that positive, luck-enhancing superstitions provide a psychological benefit that can improve skilled performance. There is anxiety associated with the kinds of events that bring out superstition."

"The absence of control over an important outcome creates anxiety. So, even when we know on a rational level that there is no magic, superstitions can be maintained by their emotional benefit."

—Stuart Vyse

Indeed, one study that examined performance in "golfing, motor dexterity, memory, and anagram games," found that making gestures, such as keeping one's fingers crossed, or uttering words, such as "break a leg" or "good luck," boosted the participants' performance.

This mechanism is mediated by increased self-confidence, write the authors.

"[T]hese performance benefits are produced by changes in perceived self-efficacy. Activating a superstition boosts participants' confidence in mastering upcoming tasks, which in turn improves performance."

'Cheap' superstitions better than costly ones

"[O]nce you know that a superstition applies, people don't want to tempt fate by not employing it," says Vyse. He goes on to cite an example of a chain letter that became famous among journalists in the US.

"Many of these journalists knew that it was bunk, but they did not want to tempt fate by not copying the letter and sending it on," says the researcher.

However, "not tempting fate" is also a popular option because the costs of abiding by the superstition are very low compared with the potential outcome.

In this case, sending the letter and employing the superstition bears little cost compared with the alleged outcome of various "calamities" brought on by bad luck, such as "lost fortunes, jobs, and lives."

Similarly, quickly knocking on a wooden surface when commenting that one has been in great health for years is a small price to pay compared with the potentially devastating consequences of illness.

One study confirms this and explains that superstitions appeal to people because the advantages of carrying around a lucky charm, for example, outweigh the disadvantages of a so-called costly exploration scenario—a situation where a person must explore an uncertain environment.

According to the authors, "superstitions that involve carrying small, lightweight lucky charms might persist because the same general learning rules for identifying causal relationships in other settings are advantageous, while here they do next to no harm."

"Similarly, [...] avoiding the number 13 may impose a relatively small cost with potentially large benefit, which might explain why this superstition persists."

Superstitions and OCD: A complex link

A person that MNT spoke to and who prefers to remain anonymous revealed that they have to set their alarm "at least 10 times every night, along with muttering some reassuring words."

Otherwise, they continued, "I feel like something negative will happen in my life. I can't stop setting my alarm until I feel at ease. I've been known to get to about 50 before."

Although such a habit may seem unusual to some people, those who perform these ritualistic behaviors often draw comfort from them. "I actually think it's a good thing sometimes—a way of keeping yourself mentally on track!" the person continued.

Sometimes, however, repeated behaviors may signal a more severe condition, such as obsessive-compulsive disorder (OCD).

"For me, superstitions cross over into OCD," said another person that MNT interviewed. "I do 'superstitious thinking' when I'm struggling with OCD, where I believe doing or thinking something will make something happen or not happen."

"An example is that I need to pick the correct pair of socks to wear; otherwise, my mum will die. So for me, [superstitions are] potentially harmful and a sign I'm not doing that well."

—MNT interviewee

Established research recognizes superstitions as an example of "compulsions performed in response to obsessions," along with "excessive hand washing, ritualized bathing or grooming, checking behaviors, mental rituals, need to repeat activities, re-reading text, [and] hoarding behaviors."

However, there has been much debate surrounding the issue of whether OCD and superstitions share a continuum. Many researchers suggest that they do not, pointing out superstitions and OCD use different brain areas.

Still, OCD and superstitions share many overlapping traits, such as performing rituals to ward off harm. Furthermore, some researchers have defined superstitious rituals as "maladaptive methods of attempting to gain control in uncertain situations."

"[L]ikewise," they continue, "compulsive behaviors are maladaptive and performed with the intent of preventing or reducing anxiety associated with the obsessive thought."

However, it's important to remember that although there seems to be an established connection between superstition and OCD, there are discrepancies in the results of the various studies that tackled this link.

Drawing the line between superstitions and OCD is a nuanced issue that healthcare professionals should handle competently and sensitively.