Many people tend to view the experience of coincidences as evidence for a variety of mysterious causal mechanisms. On the other hand, skeptics tend to dismiss the psychological experience of coincidences as a demonstration of how irrational people can be. Irrationality, in their view, means biased cognition involving weak probabilistic reasoning and paranormal beliefs. Writing in Journal New Ideas in Psychology, Johansen and Osman describe research that offers a third way: the rationalist perspective on the psychology of coincidence occurrence (2015). Rather than just being examples of irrationality, they argue that the experience of coincidences results from the rational causal learning mechanisms used in daily life.

The probability experiment

They devised an experiment to test the hypothesis that those who are unsophisticated in probability theory could not judge the probability of a coincidence. Surprisingly they found that “ordinary people” can judge coincidence probabilities fairly well.

Magda Osman, a senior lecturer in experimental psychology at Queen Mary University, and Mark Johansen of the School of Psychology at Cardiff University asked the participants to record their coincidences for periods of five weeks. The study did not define coincidences, instead, the definition was left up to participants to decide what they considered coincidences to be for themselves. The idea was to look at coincidences in the wild rather than create fictitious coincidences, such as the birthday problem.

The researchers then compiled the real-world coincidences and then asked a different set of participants to rate the probability of the coincidences occurring, and how likely they were to occur by chance. The participants were remarkably consistent in their ratings. For each type of judgment, regardless that people differed in age, gender, or educational background, they gave similar judgments on how coincidental the set of different coincidences were. They also had similar judgments as to how likely they thought the coincidences were to occur, as well as their ratings of possible causality.

This study shows that people are fundamentally attuned to judging the likelihood of various patterns of recurring events in similar ways. This challenges conventional academic wisdom that poor probabilistic reasoning leads people to misjudge the probability of coincidences. The results suggest that people tend to agree on what makes a coincidence highly unlikely or not. This requires some basic sense of probabilities in the world.

Everyday rationality is applied to coincidences

A subsequent study strongly suggests that psychological phenomena are especially relevant where coincidental events are concerned. (Johansen and Osman, 2020) Their evidence suggests that the experience of coincidences is a necessary consequence of rational causal learning mechanisms, rather than just being examples of irrationality.

People use the same properties relevant for causal reasoning when detecting and evaluating events that are ultimately judged to be coincidences. Whenever a judgment about something coincidental is going on, people actually rely on features of their daily causal reasoning. Coincidences are therefore an unavoidable feature of the human mind searching for causal structure in reality. Coincidences, then, are deeply connected with how the human mind perceives events going on in the surroundings, along with a tendency to highlight possible causal explanations. It all depends on mechanisms for inferring causality in what is going on. Coincidences are pattern repetitions that are observed to be unlikely by ordinary standards but are nonetheless attributed to chance as our attempts at causal explanation have not produced anything more plausible than mere chance. In this sense, the idea that the human mind looks for causal structure is the explanation for our need to find matches in meaning about what takes place around us.

Coincidences can be practical

Aside from the numerous conjectures about explanations for meaningful coincidence, a primary meaning is derived from their usefulness. Writing in the The British Journal for the Philosophy of Science, Van Andel (1994) collated the multiple instances Nobel Prize winners have utilized serendipity to achieve their acclaimed results. He reports that well-documented, serendipity is supported by laboratory diaries, notebooks with experimental results, scientific articles, textbooks, case histories, acceptance lectures of Nobel laureates, memoirs, autobiographies and informal talks. In talking about the serendipitous discovery of X-ray, Rontgen said that he discovered by chance rays that penetrated black paper. Apparently, he didn't think; he experimented. As elaborated by academic radiologist Morton Myers, MD, (2011), many of the medical breakthroughs of the twentieth century resulted from the happy accidents of serendipity. These include the discovery of lithium for bipolar disorder, antipsychotics and antidepressants. The mechanisms by which serendipity takes place remain uncertain except that it usually requires sagacity, the ability of the observer to see the value in the happy accident.

The value of synchronicity in psychotherapy is being supported by recent data (Roessler and Reefschläger, 2022) Again, the mechanisms are unclear, but the data are highly suggestive of usefulness.

Comment

As clearly stated by statisticians, coincidences are highly common in large populations. (Hand, 2014) They play important roles in several aspects of psychology. While many people speculate about their potential explanations, the primary explanation is psychological. Before a series of events becomes a coincidence someone has to notice it. Once the person notices the coincidence, it can be scanned for potential usefulness using the same rationality we use for other events needing examination. The practical use of meaningful coincidence requires broader research attention.