In the 1980s, a team of psychologists interviewed members of the Philadelphia 76ers about their belief in streak shooting — the notion that a player is more likely to make another shot after making a successful one. In a famous study published in 1985, the researchers discovered that NBA players, coaches, and fans alike believed in the concept.
This same study, however, also looked at the actual player’s data during the 1980-1981 76er season, as well as data from a controlled shooting experiment, and found no support for the concept whatsoever. The authors dubbed this the "hot hand fallacy":
People "see" a positive serial correlation in independent sequences, and they fail to detect a negative serial correlation in alternating sequences. Hence, people not only perceive random sequences as positively correlated, they also perceive negatively correlated sequences as random.
A study published in February 2017 in the journal Adaptive Human Behavior and Physiology argues that the long-held perception that yawns are contagious could be related to the same underlying cognitive biases:
In an abstract sense, much like the incorrect observations associated with the hot-hand fallacy [...], the observation that yawning is contagious may have arisen as a consequence of our tendency to see patterns and causation where none exists, to misinterpret the clumpiness of randomness as something else.
At issue in this study is not if yawns are contagious, but if past attempts to demonstrate their contageousness actually address that question in the first place. Among the complicating factors in the literature, according to the authors, are past methodological decisions that end up biasing results to detect yawn patterns where none actually exist, along with basic assumptions with no basis in reality and inconsistent definitions and methods between studies.
Lead author Rohan Kapitány, a postdoctoral fellow at Oxford University, explained this problem in a feature published at PsyPost:
The belief that yawns are contagious seems self-evident, but there are some very basic reasons for why we might be mistaken in this. [...] In this instance, the literature hasn’t questioned the basic features of contagious yawning, and ended up with a wide range of unstandardised methodologies and conclusions. [...]
A large body of literature in judgement and decision making, cognitive heuristics, and basic statistics can explain the phenomenon away as being illusory.
To address these issues, the authors first created a computer model to investigate how likely it would be to perceive incidental (random) yawns as contagious based on a variety of different factors. The authors demonstrate that the likelihood of perceiving yawns as contagious rises dramatically depending on how much time one considers a yawn to be contagious for:
If we accept the extreme null hypothesis (that yawns are not contagious, and the appearance of contagion is an illusion), and assuming [a yawn is contagious for one minute], then 12.10% of all yawns would be incidental, but would otherwise be incorrectly categorized as contagious. This value explodes to 47.87% if we assume yawns are contagious for 5 min.
With this result in mind, the authors then performed a real-world version of those simulations. Their experiment broke 79 students into groups and had them listen to "Chopin’s Complete Nocturnes", some with blindfolds, some without. Throughout the session, each participant was filmed in order to count yawns and analyze their occurrence. As argued in the study, the initial results could be interpreted as evidence that yawns are, in fact, contagious:
Data from the blind-folded session revealed that participants produced, on average, two-thirds a yawn per hour [...]. When participants could see each other, they produced considerably more yawns (about 3.5 yawns per hour, or one yawn every 15–20 min), particularly when they could see each other in the second session rather than the first.
However, a closer look at the data raised the possibility, they argued, that these increases in yawns were not the result of something triggered by another person’s yawns, but of the individual person yawning in their own clusters of yawns — that aforementioned "clumpiness".
The authors found that more than 95 percent of each of an individual's yawns happened within a 5-minute window of one of their own yawns, raising the possibility that any pattern of correlation between yawns could be an artifact resulting from the fact that people yawn in clusters — something termed autocorrelation.
Further complicating the yawn contagion hypothesis is the fact that there seemed to be no clear temporal relationship from when one person yawned to when another person yawned. As explained in PsyPost:
When the researchers analyzed the timing, they found that a yawn at any given moment did not reliably produce a yawn from another person within 3 minutes. So while people yawn more often in social settings, yawns themselves did not appear to be contagious to others.
The authors proposed a more nuanced hypothesis: that humans "produce more yawns in social contexts, even though yawns themselves may not cause additional yawns in others". They argue, in essence, that the perceived cause-and-effect of one person’s yawn on another — like the perceived effect of a Philadelphia 76er’s successful shot making a second one more likely — could simply be the residual effect of how we perceive and recall those yawns, combined with the fact that yawns typically occur in clusters, and that people yawn more in social settings.
This is no minor claim, as Slate’s Daniel Engber explained:
If Kapitány is right, then we’d have to reckon with three decades’ worth of faulty research. It would mean that all these studies of contagious yawning [...] have been trafficking in false-positive results.
The authors do not suggest that their study conclusively proves their hypothesis, but Kapitány argues his results highlight a need to be more rigorous in how this kind of study is approached:
I may be wrong! [...] Maybe yawns are contagious! But if yawns are contagious, I would love to see more robust attempts to falsify the claim and specifically describe the phenomenon, rather than simply demonstrating it over and over in slightly different contexts with richer and richer explanations.
SUNY Oneonta professor Andrew Gallup, a "prolific scholar of the yawn" also interviewed for the Slate piece, was much more confident in the contagiousness of yawns:
As far as I’m concerned, there’s no debate over whether yawning is contagious in humans.
Where does this leave us? One could convincingly argue it leaves us no better off in our knowledge of yawns than before the study. Another conclusion, equally valid, would be that this study has revealed potential problems in how "yawn contagion" studies are conducted that will be of great benefit to future studies.
Unfortunately, according to Gallup, there isn’t a great deal of funding in the yawn sciences these days.