A yawning gap

Jim Horne wonders why more psychologists aren't fascinated by yawning.

Yawning has something to do with boredom or sleepiness. Despite it being a universal human behaviour, that's about as much as we know about it. Perhaps the topic itself can seem too dull to excite us psychologists; I hope to begin to stimulate you into action.

Let's go back around a hundred years. In what must remain one of the most tedious and unexciting of investigations, Dr Carl Mayer X-rayed numerous people attempting to yawn. Being thorough and methodical he also probed their throats with laryngeal mirrors and persistently palpated their necks. It all culminated in his confident claims that yawning could be divided into three precisely timed and distinct phases: 'Initial inspiration', taking between 1.9 and 4.3 seconds, 'Acme', lasting exactly 2.3 seconds, and 'Expiration of 4.5–7.8 seconds duration'. As to why we yawn, Mayer dismissed it with two words – 'cerebral fatigue'.  

Astute physicians and scientists lost for an explanation for a phenomenon will often give it an impressive new name, usually derived from the latin. For yawning, it’s ‘oscitation’ from ‘oscitare’ (to open the mouth wide). Added to this are ponderous explanations, for example, a well-known medical textbook declared it to be, 'a deep inspiration carried out with widely opened glottis, typically with open mouth, and frequently accompanied by movements of the arms etc… it is caused by certain psychic influences.' ‘Pandiculation’, is the term given to any accompanying stretching, derived from the Latin ‘pandiculari’, to ‘stretch oneself, 

The Victorians had various theories about yawning, most of which can best be described as ‘imaginative’. For example, that yawning boosts alertness, as the widening lower jaw squeezes the thyroid gland, located in the neck below, to release more of its hormone, thyroxine, that increases body metabolism. Certainly, yawning causes a momentary increase in heart rate, but this is a reflex associated with any deep inspiration, and is followed by a heart slowing on expiration. Many early psychiatrists took a keen interest, with some strange concepts. For example, in patients with schizophrenia, yawning was seen as a good prognosis, supposedly to show that the patient wants to maintain contact with the real world.   

The idea that yawning ‘aerates’ the lungs and increases the oxygen supply to the brain is nonsense, as inhaling oxygen doesn’t suppress the urge to yawn. If anything, yawning leads to a fall in oxygen levels, as breathing usually ceases for a while after a yawn. The belief that that yawning wakes us up or otherwise combats sleepiness to increase arousal, has been discounted by Guggisberg et al (2010) who, in their review, point out that EEG recordings and measures of autonomic activity before and after yawning in healthy participants show no consistent increase in arousal levels. Moreover, incidental findings from sleep clinics that happen to be measuring the EEG of sleepy patients, find no changes in brain activity after a yawn. 

Although yawning clearly has ‘something psychological about it’, surprisingly few psychologists have investigated it, until fairly recently (see below). One of the most entertaining early accounts was by Dr Joseph Moore from the George Peabody College in Tennessee, who ran a series of experiments in 1941. The first employed a stooge able to yawn at will, who sat in a nearby public library reading room, in full view of other readers. He yawned obtrusively every ten minutes whilst Moore sat unobtrusively in an overlooking gallery, recording the events in his notebook. Within a minute or so of each rendition almost half of the unwitting audience would follow suit. Another of Moore’s studies was more blatant, with a short movie of a person yawning, shown to an unsuspecting audience, and soon followed by a doubling of the incidence of yawning among the onlookers. To determine whether yawning can be stimulated simply by hearing it rather than seeing the yawner, he played gramophone records of yawning to college students, with little response. But when played to blind students they yawned profusely.  

As to why we cover our mouths when we yawn, is it embarrassment, or as it was thought by the ancient Greeks, to prevent one’s soul from leaving the body? Although yawning and stretching are found in many mammals, such contagious yawning has also only been seen in chimpanzees. 

Obviously, we yawn when sleepy, but it is also found under fearful and stressful situations, as was commonly observed during the First World War, in troops waiting in the trenches for the ‘whistle to blow’ and the order to ‘go over the top’ and confront the enemy. It is also seen in athletes before a competitive race, with actors before going on stage, and in migraine sufferers just before an attack (cf. Provine 2012). 

Contagious yawning

Nowadays, the focus has remained on contagious yawning. For example, arguably the largest systematic study, by Bartholemew and Cirulli (2014), recruited a total of 328 healthy participants who were shown a 3-minute video, when the incidences of yawning were assessed.  This was followed by a cognitive battery, and a ‘comprehensive questionnaire’ including measures of empathy, ‘emotional contagion’,‘circadian energy rhythms’ and sleepiness. Those individuals less susceptible to contagious yawning were found not to be suppressing it, as they reported not even feeling like yawning. Unlike previous findings that empathy, time of day, and intelligence seem to influence contagious yawning susceptibility, Bartholemew and Cirulli found no such effects once age was accounted for, as yawning decreased even for those within the range 20-40 years. Nevertheless, as age was only able to explain 8% of the variability in this yawning response, they had to conclude that the great majority of the remaining variability was unexplained. 

This conclusion is endorsed by a 2017 extensive review on contagious yawning, by Massen and Gallup. It covered the ever-growing body of bewildering findings mostly concerned with the connection between yawning and empathy, and whether for example, this emotional contagion fits various models as outlined by the reviewers, such as a ‘primitive form of empathic processing known as State Matching’, or what was referred to as the ‘Perception-Action-Model’.

However, fundamental questions remain, such as whether people who are more empathic are more susceptible to contagious yawning, and whether thinking about yawning can trigger yawns, and do attempts to shield a yawn stop its contagion? Is it really the case that that we’re more likely to catch a yawn from relatives than acquaintances, and more likely to catch them from acquaintances than strangers? Are children with autism immune from contagious yawning

As to the role of boredom as a cause of yawning, Massen and Gallup wisely noted that it seems rather unlikely that people suddenly become bored when they see someone else yawning during exposure to uninteresting stimuli. Sadly, despite all this research, the reviewers were led to the anti-climax, 'Future research examining links between contagious yawning and empathy requires more rigorous investigation involving objective measurements to explicitly test for this connection' (p.582).  

Other recent ideas about contagious yawning include keeping the brain cool, as reviewed by Gallup and Eldakar ( 2013) who pointed out rather presumptuously, that ‘no study has found evidence contrary to these findings’ (p1). Which included one of their own findings that sleepy people sitting with ice-packs on their foreheads were less susceptible to contagious yawning. A rather bizarre study, by Massen et al (2014), involved ‘120 pedestrians’ who were sampled for susceptibly to self-reported yawn contagion over the summer and winter, when there were distinct environmental temperature differences. The authors concluded ‘as predicted, the proportion of pedestrians reporting yawning was significantly lower during winter than in summer, with temperature being the only significant predictor of these differences across seasons’.  

Sleepiness

It is perhaps surprising that sleep research has paid little interest in yawning as an index of sleepiness in those people presumed to need sleep, even when the participant is alone and ostensibly free of contagious yawning effects. But then there is the confound of boredom, of course. However, given the range of well-established, sensitive and objective measures of sleepiness (cf. Horne 2016), then one can see why such little attention has been paid to yawning, here. 

So, to end on a lighter note, I have to conclude that yawning gaps still remain in this field of exploration. Ironically, such an uninspiring conclusion might have the remarkable effect of being able to stimulate in, you, dear reader, the very phenomenon under discussion.

- Jim Horne is Emeritus Professor of Psychophysiology at Loughborough University. [email protected]

References 

Bartholomew A.J. & Cirulli E.T. (2014). Individual variation in contagious yawning susceptibility is highly stable and largely unexplained by empathy or other known factors. PLoS One. 9(3):e91773. doi: 10.1371

Gallup AC & Eldakar OT (2013). The thermoregulatory theory of yawning: what we know from over 5 years of research. Front Neurosci. 2013 Jan 2;6:188. 

Guggisberg AGMathis JHess CW. (2010) Interplay between yawning and vigilance: a review of the experimental evidence.Front Neurol Neurosci. ;28:47-54

Horne, J. (2016). Sleeplessness – assessing sleep need in society today. Palgrave Macmillan

Massen JDusch KEldakar OTGallup AC. (2014) A thermal window for yawning in humans: yawning as a brain cooling mechanism. Physiol Behav. 130:145-8. 

Massen, J. & Gallup, A. (2017). Why contagious yawning does not (yet) equate to empathy. Neuroscience & Biobehavioral Reviews, 80: 573-585

Provine R. (2012). Curious Behavior: Yawning, Laughing, Hiccupping, and Beyond. Harvard University Press.

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