Why do people catch a yawn?

seal pup having a nap

(reading time: 2 mins)

No, don’t yawn. You’ll set me off…..

As infectious yawning is only found in apes and humans, the unanswered question of why we do it keeps drawing in the research dollars. Consensus seems to be settling on contagious yawning as a form of social bonding. But I wonder if our hunter-gatherer ancestry means there’s more to it than a symbol of simple social cohesion, unrelated to sleep?

Yawning in company frequently co-incides with active mirror neurons located in the more primitive parts of the brain. Mirror neurons cause us to smile or laugh when others do, expressing a basic commonality which reinforces social bonds. Studies with less neurotypical groups, such as those on the autistic spectrum for whom social cues are less apparent, show a significant reduction in yawning following others1. And interestingly yawning is rare in children under the age of 4, suggesting that while a primitive part of the brain may be involved, the behaviour requires a certain level of social development.

While it may be true that yawning is associated with tiredness when we’re alone, this seems to have little influence when catching a yawn from others. So while imitation may be the sincerest form of flattery (as the old saying goes) and collective yawning re-enforces social bonds, perhaps the infectious yawn has one additional element which has contributed to human survival?

Apes and early humans survived by living in close social groups with high levels of mutual dependency. Bedding down for the night would always mean some risk. Perhaps a yawn signals members of the group are getting tired, so others unwittingly copy this behaviour and then turn their attention to sleep. The contagious yawn is therefore a signal it is time for the whole group to prepare for rest. This likely includes working out where members will sleep with regard to risk from predators, exposure to the weather, expressing the group’s social order etc.

A recent study looked at why teenagers are frequently hopeless until late morning while conversely the elderly tend to rise early2. The suggestion is that for early humans, having a range of times when group members were awake and acting as sentries increases the groups’ odds of survival.

So perhaps the purpose of the contagious yawn is a warning that the group needs to prepare for a time when it will be at its most vulnerable?


1. Yawning less common in children with ASD https://today.uconn.edu/2010/09/when-yawning-isnt-contagious

2. A study of the Hadza people in Tanzania shows age based sleep patterns https://today.duke.edu/2017/07/live-grandparents-helped-human-ancestors-get-safer-night’s sleep

2 thoughts on “Why do people catch a yawn?”

  1. A six month laugh?! Sounds like something in the water, or an attempt at a Guinness world record.

    One comment on the last part though, it’s easy to mythologise human intelligence as being in a different class to other species. Certainly wild animals focus the majority of their effort on survival out of necessity, whereas the wide human range of activity is because having such control over our environment, we have time and energy to spare.

    But other species do play without any clear evolutionary purpose. There are even wild animals that seem to enjoy ball games – here’s a Swedish cow apparently having a great time, https://www.facebook.com/uniladmag/videos/cow-plays-fetch-with-new-ball/238215183512461/ and here’s a deer on a volleyball court, https://www.youtube.com/watch?v=geKDQeIMWYw And the BBC’s Spy in Pod series was fascinating. This is a ‘co-alition’ of young dolpins who are hanging out with their new mates, knocking a ball around and getting off their heads – sounds like a good lad’s night out! https://www.youtube.com/watch?v=msx3BAhIeQg

    So I assume that all life, and in fact the universe itself, has a degree of curiousity and play built in, but circumstances don’t always make that apparent.

  2. Unlike consciousness, yawning really IS a “hard problem”.

    A point not made here is that, at least for we snout-less apes, the yawn is often a symptom of boredom rather than just sleepiness. Perhaps a signal (transmissible to the group) of disinterest in a subject or activity? This being an exaption from some more primitive physiological requirement?

    A hard problem indeed!

    Laughter, too, tends to be infectious: Snippet from one of my earlier books follows.

    So what’s the Joke?

    Well, why do we laugh? How could this odd behaviour pattern have evolved and what purpose does it serve? There seem to be four quite separate aspects to laughter.

    Physical play-laughter.
    The earliest play that a baby experiences is the tickle. This typically produces a lot of chuckling, to the mutual delight of both tickler and ticklee and perhaps plays a significant role in bonding. This kind of laughter persists in later life, even in the adult, during the course of all manner of informal games, particularly chases. Here, too, bonding is being rewarded with joy although, especially in the child, practice for later fight, flight or hunting situations plays a large part. This kind of laughter is not uniquely human. Equivalent behaviours have been in observed in many mammals including rats and chimpanzees.

    Communicative laughter.
    The facial muscle configuration which is a precursor of laughter, the smile, is used to convey many kinds of emotion, usually, but not exclusively, pleasant and cheerful. It is pretty standard for a greeting, indicating the absence of hostile intentions. Laughter, too, is used to enhance language and can take many forms. The nervous chuckle, the conspiratorial giggle, the polite response laugh and various social affectations. And sometimes negative emotions such as sarcasm or scorn are expressed this way.

    The contagious laugh.
    This rather strange phenomenon can be most plausibly explained as a relic of the early parent-child interaction. It is widely used in radio and TV shows to increase audience reaction although, particularly if overdone, the reaction is not always that intended – Yuk! It is reported that in Tanganyika a widespread epidemic of contagious laughter lasting six months occurred among schoolgirls.

    Humour – the Joke.
    In contrast to all the other aspects of laughter this one is exclusive to we Humans. Just as no other animal asks the question “Why?”, neither can any other creature see the joke. Any joke! An important component of Imagination is pattern recognition, the primary function of we navigators. When we do a particularly good job of recognizing a pattern the society of cells rewards us in some way so as to encourage us to keep up the good work. Because, in the long run this tends to enhance survival. As a reward for spotting certain kinds of incongruity it simply taps into the already established laughter mechanism with its associated pleasure centres. Humour is an exaption of the basic laughter mechanisms common to many other mammals. It is almost always associated with the perception of incongruity.
    Other explanations have been suggested. One particularly ingenious mechanism has been proposed by Vilayanur Ramachandran. He suggests that laughter acts as a kind of “all clear” signal that will distinguish between a trivial event and one having serious consequences. The reasoning he supplies to support this, however, appears far from watertight and, in any event, doesn’t cover the majority of humorous situations.
    A prime example is the pun, a purely language based form of humour which lies at the heart of the greater part of comedy. The pun, the double entendre, clearly demonstrates a context inappropriate to its implied meaning. We detect the incongruity as the penny drops. How droll! The society of cells switches on the laughter pleasure centres to metaphorically pat us on the head. Good Boy (or Girl). Good Navigator!

    Other “Spot the pattern” prizes

    We get so used to doing stuff that we take it all for granted. Have you ever thought how odd it is that we do all the things we do? Or how small is the range of activities of other animals? Even large mammals? Well, they forage for food and eat. They attract, or seek, a suitable partner and mate. They give birth and sometimes tend their young. The young may play a little to get a bit of practice in for life. Really that’s about it! Sure there’s the odd sideline here and there. The dog might enjoy a bit of sniffing around and peeing up lamp-posts and the bird might sit up the tree having a good old sing song. But even these are really tied pretty closely to their basic functions.
    When did you last see animals having a game of football? Or playing in a band? Doing a crossword? Line dancing? Using a lathe? Painting a picture? Well, I could quite easily pad this book out another three hundred pages with such questions, but I am sure that you, gentle reader, being a very fine navigator, have now well and truly got my drift. None of these sports, games, hobbies or pastimes are directly related to nutrition, reproduction or survival. Together with even such passive things as watching TV, reading a novel or listening to the radio, they are activities we do because just because we enjoy them. There are admittedly some unfortunates who just do some of these things out of habit or as a result of compulsive disorders. But, in general, we engage in these activities because we get some kind of kick out of them. They are fun. And what is the source of fun, enjoyment, satisfaction? It is, again, the society of cells giving us a reward for performing pattern recognition.
    That is something which might not, at first glance, seem obvious. But when you stop to think about it more analytically it becomes clear that pattern recognition is the common factor and the ultimate source of pleasure in all these uniquely human behaviours. Patterns coming from and going to our muscles, from vision, from hearing, from olfaction, from touch, in various combinations. If, for example, you are singing and dancing to music, just about all these can be turned on. That’s why many find that very exhilarating and enjoy partying. Others might enjoy the quieter pattern recognition of chess. The human society of cells uniquely provides such rewards because, unlike the bodies of other animals, it employs a very fancy navigator. As with other animals, we also get rewards for copulation and eating and caring for young. But we probably even strike a bonus in these as well. Since, because we have this huge Imagination and a correspondingly greater self awareness, we probably get to enjoy these activities much more too!

    Ain’t we the lucky ones?

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