INTRODUCTION
“A yawn is quite catching you see, Like a cough,
It just takes one yawn to start other yawn off.”
- Dr. Seuss (Sleep Book, 1962)
The topic of yawning was chosen for this experiment, because it is a very common neurological occurrence, about which much is speculated and little is known for certain. There are many theories as to what factors influence the production of yawns, as well as whether or not — and to what degree — yawns are contagious. However, much of yawning remains a mystery to the everyday observer. In particular, there has been little said about the extent to which yawning is subconsciously contagious, as opposed to the extent to which it is consciously contagious. This experiment seeks to investigate many common and not-so-common factors’ affect on yawning, as well as to compare the contagiousness of yawning through subconscious and conscious testing.
A yawn is a slow, wide opening of the mouth and consecutive slow inspiration of breath followed by a much shorter expiration. The word for this “stereotypical reflex” comes from the Old English word ganien, which means to open wide or gape (Provine, Encyclopedia of Sleep and Dreaming, Scientific American, 2002). In the words of R.R. Provine, a yawning expert, “once the neurological machinery in our head gets underway, it’s hard to stop a yawn” (7). The yawn is a fairly formulaic procedure, which, if not carried through fully, is unsatisfying. A yawn with closed lips or teeth is more difficult and less satisfying. The entire process of a typical yawn takes about 6 seconds to reach completion and can occur at intervals averaging one minute apart. Both humans and animals have a regular, easily recognizable form for yawning (Provine, Encyclopedia of Sleep and Dreaming). The earliest yawn occurs approximately eleven weeks after conception. The hypothalamus is the region of the brain that plays an important role in yawning (). Certain neurotransmitters are reported to produce yawns if inserted into the hypothalamus of the animal brain. ()
There are a variety of conjectured purposes of yawning. Popular belief suggests that people yawn when they are tired or bored. In fact, sleepy people do yawn, but non-sleepy people yawn as well. Most yawning does occur before entering a state of sleep or after waking. People usually yawn when stretching, but do not typically stretch when yawning. (Provine, Encyclopedia of Sleep and Dreaming) Pandiculation is the name given to the act of stretching and yawning. () Hemiplegics, people with paralysis of the right or left side of their bodies, are unable to separate the respiratory and vasomotor components of yawning and consequentially are known to perform involuntary “associated” stretching movements of their otherwise paralyzed arm while yawning. Yawning may have possibly evolved as a craniofacial component of a general stretch action, as the facial stretch of yawning is certain to alter intracranial pressure and blood flow.
Bored people also tend to yawn, but the further reason for this is uncertain, although there are several possibilities as to why. Another theory accounting for why yawning occurs is low level of oxygen or high level of carbon dioxide in the blood. However, tests have shown that having people breathe 5% carbon dioxide mixtures (over 100 times that in typical air) raises the breathing rate but not the yawning rate. (Provine, Encyclopedia of Sleep and Dreaming) Proof that low level of oxygen is not the singular reason for yawning comes from the fact that fetuses yawn in utero even though their lungs are not yet ventilated. However, low oxygen in the paraventricular nucleus (PVN) of the hypothalamus of the brain can induce yawning. (Scientific American, 2002) Gender might affect at least the length of yawning. One test showed 17-19 year-old participants music videos and an uninteresting color test bar, producing 3.41 yawns and 5.78 yawns in 30 minutes, respectively. The yawns of males in the experiment had a longer duration than those of females. ()
One general theory accounting for the association of yawning with fatigue and boredom is that there is a homeostatic function to yawning, in that the act allows one to maintain an optimal level of activity. (Provine, Encyclopedia of Sleep and Dreaming) This is to say, people tend to yawn in situations where there is nothing to stimulate them “but it would be bad to lose the level of arousal.” (Adams, 1998) This theory accounts for all of the various presumed purposes of yawning. A tired or bored person would yawn in order to maintain an optimum level of cranial and corporeal activity. Their body might be attempting to fall asleep or “zone out,” while they, in essence, would be attempting to revitalize their systems. The association of low oxygen with yawning could be related to the necessity of oxygen for mental and physical exertion. Yawning, if truly serving a homeostatic function, could provide that extra boost needed by organisms suffering from lack of oxygen.
It is possible that yawning occurs in order to prepare an animal for a change of pace. Ronald Baenninger tested people with motion-sensitive wristbands, telling them to press a button each time they yawned. He found that yawning tended to precede periods of activity.(Adams, 1998) It is not uncommon for runners to yawn before meets.
Clinically, a variety of conclusions and observations have been drawn regarding yawning. Yawning is recorded to be a symptom of some human diseases, such as motion sickness, chorea, brain tumors, hemorrhage, and opiate withdrawal. The act is also stimulated by some hormones (i.e. testosterone, oxytocin, corticotrophin, melanocyte-stimulating hormone…) and drugs (apomorphine, piribedil, pilocarpine…). Interestingly enough, schizophrenics are reported to yawn rarely. With regard to the believed excess amount of dopamine in the schizophrenic brain and also the purported production of yawns by antidopaminergic drugs suggests an association with yawning and the monoamine neurotransmitter dopamine. In terms of neurotransmitters, yawning is associated with cholinergic and peptidergic excitation and dopaminergic inhibition. Unconfirmed clinical folklore says that patients suffering from acute physical illness never yawn when their condition is serious. Thus, resumed yawning after a period of respite can be interpreted as an indication of recuperation. Additionally, yawning serves to prevent atelectasis, a frequent postoperative respiratory complication. (Provine, Encyclopedia of Sleep and Dreaming)
It is more than likely that there are a variety of functions of yawning. It is also comfortable, and serves to equalize the pressure between the ambient environment and the middle ear. For this reason, many people yawn when experiencing discomfort at high altitudes. On one survey conducted, the average rating for yawning on a 1(bad) to 10 (good) scale was an 8.5. (Provine, Encyclopedia of Sleep and Dreaming)
The neural circuits required for yawning are probably in the brainstem not far from other respiratory and vasomotor centers. (Provine, Encyclopedia of Sleep and Dreaming)
Yawning might be a method of communication, through which humans can communicate changing environmental or inner-body conditions to others. This could simply be a logical conclusion resulting from the theory of yawning as a homeostatic function. In the process of attempting to maintain homeostasis and counter change, the organism could be communicating an impending change. Thusly, if yawning does, in fact, serve a communicative purpose, this would account for the obvious contagiousness of yawning in serving to synchronize behavior within groups. If yawning serves this purpose, it is most likely that the mechanism is vestigial and has lost its evolutionary significance. Observing, hearing, or thinking about yawning can trigger the act. Yawning itself involves reactions between the unconscious brain and the body. (Scientific American, 2002) However, it is important to note that a person does not yawn every time a yawn is observed, heard, or referred to. Although there are certain factors that obviously play a role in triggering yawns, it is unclear why these conditions only sometimes trigger yawns and which factors influence yawning and to which degrees. It is important to note that laughter, too, is contagious. (Provine----uHHH)
One experiment reported in the Journal for Cognitive Brain Research tested the contagiousness of yawning. It was hypothesized that yawning was part of a more general phenomenon known as mental state attribution, the ability to inferentially model the mental states of others. The experimental results showed that “susceptibility to contagiously yawn was positively related to performance on self-face recognition and faux pas theory of mind stories, and negatively related to schizotypal personality traits.” Therefore, the experimenters attribute yawning to an unconscious empathic modeling. (Platek, Critton, Myers, Gallup, 2002)
This experiment is investigating the question, “What is the effect of various stimuli — especially subconscious and conscious references to yawning, but also factors such as boredom level, amount of sleep, gender, homeostatic activity, and thirstiness — on the number of yawns occurring?” The research hypothesis for the experiment is that “changing various stimuli — instituting various conscious references to yawning, decreasing amount of sleep, increasing boredom level, increasing homeostatic activity, and increasing thirst level — will all increase the number of yawns occurring. Gender will have no effect on the number of yawns occurring. At the same time, however, instituting various subconscious references to yawning will not increase the number of yawns occurring.” The null hypothesis is that none of the tested factors will affect the number of yawns occurring.
BIBLIOGRAPHY
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RESULTS
56 people were tested. This total does not include the various participants whose results were discarded for a particular reason, such as if he or she was not visible on the video for the duration of the experiment or turned out to know the purpose of the project before experimentation. Out of the 56 people tested, 33 did not yawn and 23 did yawn. 15 of the 23 yawned only once, while the other 8 yawned more than once. 16 females and 40 males were tested. The ages of the participants ranged from 14 to 18 years old.
Table 1. The Effect of Type of Stimulus on Yawning
Section / Total Number of Yawns / Percentage of Total Yawnsduring video / 8 / 25.00%
during Wordlist A / 0 / 0.00%
during Wordlist B / 1 / 3.13%
during survey / 13 / 40.63%
after informed* / 10 / 31.25%
TOTAL / 32 / 100.00%
The experiment was investigating the effect of various stimuli on the number of yawns occurring. Most directly, the media through which the idea of yawning was projected was traced with regard to the percentage of total yawns that media produced. 8 yawns occurred during the video clip, which showed a man yawning, 0 yawns during the reading of Wordlist A, which contained the word “yawn” twice, 1 yawn during the reading of Wordlist B, a control that did not contain the word yawn, 13 yawns while filling out the survey, and 10 yawns after the participants were informed of the nature of the experiment. The first three sections of experimentation represent subconscious stimuli, the fourth section, the survey, represents a semi-conscious stimulus, and the last section represents a conscious stimulus.
Table 2. The Effect of Sleep on Yawning
Of those that: / Average Hours of Sleep the Previous Nightyawned / 6.87
yawned once / 7.03
yawned more than once / 6.56
did not yawn / 7.43
The participants were asked to estimate the amount of sleep they received the previous night. Those who yawned got an average of 6.87 hours of sleep, while those who did not yawn got an average of 7.43 hours.
Table 3. The Effect of Homeostatic Index on Yawning
Of those that: / Average Homeostatic Index* (out of 10)yawned / 1.57
yawned once / 1.8
yawned more than once / 1.38
did not yawn / .48
The homeostatic index for each participant was calculated in the following way:
ds – ws = homeostatic index
ds = (d sub s) demand for awareness; self-assessment rating (scale of 1-10, 10 being most awake)
ws = (w sub s) wakefulness; self-assessment rating (scale of 1-10, 10 being stay awake, 1 being sleep)
On the survey filled out by all participants, the participants were asked in question 2 to rate on a scale of 1-10 (10 being most awake) how tired they are and then in question 3 to rate on a scale of 1-10 (10 being stay awake, 1 being sleep) what they need to do in response to outer demands. Question 3 was phrased in the following way: “Rate on a scale of 1-10 (10 being stay awake, 1 being sleep) what you need to do right now in response to outward demands. (For example, if you just came from, are returning to, or are in a very demanding class where you need to pay attention to keep your grade up, you might be a 8, 9, or even a 10).” The homeostatic index relates to the theory that yawning serves a homeostatic function. Thus, a greater difference between wakefulness and demand for awareness denotes a greater degree to which the body might be attempting to maintain awareness.
The average homeostatic index for those that yawned was 1.57, while it was only .48 for those that did not yawn.
Table 4. The Effect of Perceived Wakefulness on Yawning
Of those that: / Average Wakefulness Rating (out of 10)yawned / 5.39
yawned once / 5.33
yawned more than once / 5.5
did not yawn / 7.43
The average wakefulness rating on a scale of 1-10 (10 being most awake) for those that yawned was 5.39 and 7.43 for those that did not yawn. The participants rated themselves.
Table 5. The Effect of Perceived Boredom on Yawning
Of those that: / Average Boredom Rating Before Testing (10 being most bored) / Average Boredom Rating During Testing (10 being most bored) / Percent Who Describe Selves as “Easily Bored”yawned / 5.13 / 5.39 / 65.22
yawned once / 4.8 / 4.6 / 53.33
yawned more than once / 5.75 / 6.88 / 75
did not yawn / 5.82 / 5.48 / 54.55
65.22% of those that yawned described themselves as “easily bored,” while only 54.55% of those that did not yawn described themselves as “easily bored.” For the boredom ratings, the students rated themselves.
Table 6. The Effect of Thirstiness on Yawning
Of those that: / Percent Thirstyyawned / 73.91
yawned once / 73.33
yawned more than once / 75
did not yawn / 57.58
73.91% of those that yawned were thirsty during testing, while only 57.58% of those that didn’t yawn were thirsty.
Table 7. The Effect of Oxygen Deprivation on Yawning
Of those that: / Percent Short of Breathyawned / 8.70
yawned once / 13.33
yawned more than once / 0
did not yawn / 9.09
8.70% of those that yawned were short of breath and 9.09% of those that did not yawn were short of breath.
Table 8. The Effect of Gender on Yawning
Of those that: / Percent Maleyawned / 26.09
yawned once / 26.67
yawned more than once / 25
did not yawn / 30.30
TOTAL TESTED / 28.57
26.09% of those that yawned were male, 30.30% of those that did not yawn were male, and 28.57% of the total tested were male.
CONCLUSION
The experiment was investigating the question, “What is the effect of various stimuli — especially subconscious and conscious references to yawning, but also boredom level, amount of sleep, gender, homeostatic activity, and thirstiness — on the number of yawns occurring?” The research hypothesis for the experiment is that “changing various stimuli — instituting various conscious references to yawning, decreasing amount of sleep, increasing boredom level, increasing homeostatic activity, increasing thirst level — will all increase the number of yawns occurring. Gender will have no effect on the number of yawns occurring. At the same time, however, instituting various subconscious references to yawning will not increase the number of yawns occurring.” The null hypothesis is that none of the tested factors will affect the number of yawns occurring. The research hypothesis was supported by the results.