WEBVTT - Why Do We Yawn, and Why Is It Catching? 0:00:01.840 --> 0:00:07.600 Welcome to Brainstuff, a production of iHeartRadio. Hey, brain Stuff, 0:00:07.680 --> 0:00:12.320 Lauren Vogelbaum Here. Next time you're in a meeting or 0:00:12.320 --> 0:00:16.440 a group discussion, you can try a little experiment. Take 0:00:16.560 --> 0:00:20.079 a big yawn, covering your mouth out of courtesy, and 0:00:20.200 --> 0:00:24.200 watch to see how many people follow suit. There's a 0:00:24.239 --> 0:00:27.200 good chance you'll set off a chain reaction of deep 0:00:27.280 --> 0:00:31.680 breaths and wide open mouths, and before you finish listening 0:00:31.680 --> 0:00:35.000 to this episode, it's likely that you'll yawn at least once. 0:00:35.640 --> 0:00:38.640 Don't misunderstand. We don't intend to bore you here, but 0:00:39.080 --> 0:00:42.199 just thinking about yawning can make you do it it 0:00:42.320 --> 0:00:44.960 just as seeing or hearing someone else yawn makes us 0:00:44.960 --> 0:00:48.520 do it too. My jaw, for the record, is practically 0:00:48.720 --> 0:00:53.120 itching right now, holding one back. But why do we 0:00:53.200 --> 0:00:57.920 yawn in the first place, and why is it so contagious? Today, 0:00:58.120 --> 0:01:01.200 let's talk about what we know and don't know about yawning. 0:01:02.840 --> 0:01:06.560 Yawning is an involuntary action that causes us to open 0:01:06.600 --> 0:01:10.200 our mouths wide and take a deep breath. Oh, we 0:01:10.319 --> 0:01:13.520 know it's involuntary because we do it even before we're born. 0:01:14.120 --> 0:01:17.200 Yawning has been reported in fetuses as early as eleven 0:01:17.280 --> 0:01:21.000 or twelve weeks old. It's been linked to healthy progress 0:01:21.160 --> 0:01:24.520 during early brain and facial muscular development from around twenty 0:01:24.520 --> 0:01:28.679 four to thirty weeks in grown adult humans. While we 0:01:28.760 --> 0:01:33.240 typically associate yawning with relaxation and drowsiness, your heart rate 0:01:33.280 --> 0:01:35.960 can rise as much as thirty percent during a yawn. 0:01:37.040 --> 0:01:39.480 When we yawn, we increase the flow of blood to 0:01:39.520 --> 0:01:44.000 the brain, so yawning is also assigned or cause of arousal. 0:01:45.000 --> 0:01:47.520 Many parts of the body are in action when you yawn. 0:01:48.120 --> 0:01:51.800 At first, your mouth opens and your jast stretches powerfully, 0:01:52.080 --> 0:01:54.800 allowing as much air as possible to be taken in 0:01:55.280 --> 0:01:58.360 an increasing blood flow to the neck, head, and face. 0:01:59.600 --> 0:02:03.840 Inhale well slowly and deeply, meaning your abdominal muscles flex, 0:02:04.000 --> 0:02:08.079 and your diaphragm contracts and pulls down underneath your ribcage, 0:02:08.480 --> 0:02:12.000 allowing your chest to expand above it and your lungs 0:02:12.040 --> 0:02:15.600 to fill with air. The stretching in your jaw may 0:02:15.639 --> 0:02:18.760 also open up your sinus system and allow airflow there. 0:02:19.880 --> 0:02:23.560 You pause, and then you breathe out more quickly than 0:02:23.600 --> 0:02:27.640 you breathed in. Your diaphragm relaxes, curving back upward towards 0:02:27.680 --> 0:02:31.079 your lungs which deflate a bit, and your jaw relaxes, 0:02:31.320 --> 0:02:35.960 and you probably close your mouth. So this isn't just 0:02:36.040 --> 0:02:39.200 a deep breath. And we know that our bodies control 0:02:39.400 --> 0:02:43.880 yawning and breathing with different mechanisms. Yawning may serve a 0:02:43.960 --> 0:02:47.960 number of functions, especially in different animals. After all, humans 0:02:48.000 --> 0:02:51.960 are not the only animals that yawn. Other mammals, birds, 0:02:52.000 --> 0:02:56.400 and even fish dow too. Some researchers think that yawning 0:02:56.480 --> 0:03:00.320 first evolved about four hundred million years ago in jawed fish, 0:03:01.000 --> 0:03:04.639 and that pretty much all vertebrates yond spontaneously to help 0:03:04.720 --> 0:03:10.840 regulate bodily functions. Though interestingly, the duration of yawns across 0:03:10.880 --> 0:03:15.640 different species seems to be positively correlated to how large 0:03:15.639 --> 0:03:21.119 and complex that species brain is. Like, researchers analyzed over 0:03:21.160 --> 0:03:24.320 a hundred species of birds and mammals and found that 0:03:24.440 --> 0:03:30.160 animals with more brains yawn for longer. In humans, fatigue, 0:03:30.320 --> 0:03:35.280 sleep deprivation, or boredom easily bring on yns. But scientists 0:03:35.280 --> 0:03:38.120 are discovering that there's more to yawning than most people think. 0:03:39.080 --> 0:03:42.440 There's a few hypotheses about why we do it spontaneously 0:03:42.720 --> 0:03:47.880 and why it's contagious in groups. An old hypothesis that 0:03:48.080 --> 0:03:51.440 yawning helps to draw in more oxygen or remove a 0:03:51.480 --> 0:03:55.600 buildup of carbon dioxide in our bodies. This would make 0:03:55.600 --> 0:03:58.600 a bit of sense in contagious yawning because larger groups 0:03:58.640 --> 0:04:01.600 of people off put and more carbon dioxide, which means 0:04:01.600 --> 0:04:04.440 our bodies might want to act to draw in more oxygen. 0:04:05.560 --> 0:04:08.800 But this one has been disproven. Lots of research has 0:04:08.840 --> 0:04:12.040 been done on it, including by Robert Provine, who was 0:04:12.080 --> 0:04:15.880 a developmental neuroscientist at the University of Maryland, Baltimore County 0:04:16.120 --> 0:04:20.240 and a leading expert on yawning. His team found that 0:04:20.360 --> 0:04:25.240 giving people additional oxygen did not decrease yawning, and decreasing 0:04:25.279 --> 0:04:28.359 the amount of carbon dioxide in a subject's environment also 0:04:28.520 --> 0:04:33.720 didn't prevent yawning. These air makeup changes did affect subject's 0:04:33.880 --> 0:04:37.120 breathing rates, however, showing that we breathe and yon for 0:04:37.120 --> 0:04:42.640 different reasons. Furthermore, the bodies attempt to regulate blood oxygen 0:04:42.720 --> 0:04:47.000 levels couldn't explain all yawning because we know that marine 0:04:47.000 --> 0:04:51.320 mammals sometimes yawn when they're underwater and therefore not taking 0:04:51.360 --> 0:04:55.839 in air, and human fetuses in the womb aren't using 0:04:55.839 --> 0:04:59.080 their lungs to breathe either. They receive oxygen through the 0:04:59.120 --> 0:05:04.279 placenta and the millicle cord. More recently, researchers proposed another 0:05:04.400 --> 0:05:08.520 hypothesis that yawning is a way humans and other mammals 0:05:08.680 --> 0:05:13.000 help regulate our brain temperature. The brain releases a certain 0:05:13.040 --> 0:05:17.000 amount of heat, which gets dissipated partially through warmed blood 0:05:17.240 --> 0:05:20.880 flowing from the brain being replaced with cooler blood from 0:05:21.000 --> 0:05:24.160 the rest of the body. It's dangerous for the brain 0:05:24.240 --> 0:05:27.440 to get too warm in humans. Anything above one hundred 0:05:27.480 --> 0:05:31.080 fahrenheit or about thirty seven point eight celsius is hazardous, 0:05:31.360 --> 0:05:34.520 and anything above one of four fahrenheit or forty celsius 0:05:34.520 --> 0:05:39.400 can be deadly. So having an automated mechanism to increase 0:05:39.440 --> 0:05:43.000 blood flow and also ventilate the sinuses of cooler air 0:05:43.400 --> 0:05:46.960 as happens when you yawn, it seems like an evolutionarily 0:05:47.120 --> 0:05:51.360 good play. This has been proven out in rats, in 0:05:51.400 --> 0:05:55.200 which arising brain temperatures will trigger yawning, which will then 0:05:55.360 --> 0:06:00.120 decrease those brain temperatures, and it's been shown to a 0:06:00.400 --> 0:06:04.560 contagious yawning in humans. In the early two thousands, a 0:06:04.640 --> 0:06:07.400 team out of the State University of New York Polytechnic 0:06:07.440 --> 0:06:11.640 Institute led by one Andrew Gallup found that when subjects 0:06:11.680 --> 0:06:15.880 purposefully regulated their brain temperature by breathing through their noses 0:06:16.040 --> 0:06:20.240 or by using cold compresses on their foreheads, it suppressed 0:06:20.440 --> 0:06:25.200 their contagious yawning. Other participants yawned in response to video 0:06:25.240 --> 0:06:27.680 of people yawning about forty eight percent of the time, 0:06:28.160 --> 0:06:32.480 but the subjects cooling their brains only yawned contagiously nine 0:06:32.560 --> 0:06:36.760 percent of the time. Also, a research published just this 0:06:36.920 --> 0:06:40.560 year in spring of twenty twenty six indicated that yawning 0:06:40.640 --> 0:06:44.760 may help your system circulate cerebras spinal fluid and thus 0:06:44.839 --> 0:06:48.640 help remove waste materials from the brain, maybe to help 0:06:48.720 --> 0:06:51.599 get you ready for a good sleep, or maybe to 0:06:51.600 --> 0:06:54.120 help flush you out when you've failed to get a 0:06:54.120 --> 0:06:57.880 good sleep. But okay, oh, we have to talk more 0:06:57.920 --> 0:07:02.320 about that yon contagion thing. Humans are also not the 0:07:02.320 --> 0:07:05.520 only species that can catch a yawn. This has also 0:07:05.600 --> 0:07:10.880 been observed in other social species, including chimpanzees, bonaboes, lions, parakeets, 0:07:10.960 --> 0:07:14.840 and domesticated dogs. Though we should note here that the 0:07:15.120 --> 0:07:19.120 individual response of any given animal to seeing or hearing 0:07:19.200 --> 0:07:24.360 or thinking about another animal yawn can vary significantly. For example, 0:07:24.640 --> 0:07:27.800 adult humans will yawn in response to seeing a yawn 0:07:28.200 --> 0:07:32.200 something around sixty percent of the time. A recent study 0:07:32.200 --> 0:07:35.200 has shown that a fetus will yawn about half the 0:07:35.240 --> 0:07:39.160 time that it's mother yawns about a minute afterwards, perhaps 0:07:39.280 --> 0:07:43.120 due to some kind of physical or chemical prompt But 0:07:43.440 --> 0:07:46.400 after a child is born, yawns don't seem to be 0:07:46.480 --> 0:07:49.200 catching until the kidd in question is four or five 0:07:49.280 --> 0:07:53.960 years old. Perhaps coincidentally, this is around when children usually 0:07:54.040 --> 0:07:59.160 start developing a sense of empathy, so there's another hypothesis 0:07:59.200 --> 0:08:02.440 that contagious year yawning is a test of empathetic response. 0:08:03.760 --> 0:08:06.960 This is backed up by the observation that chimpanzee infants 0:08:07.000 --> 0:08:12.480 don't yawn contagiously either, and whether bonibo catches a yawn 0:08:13.000 --> 0:08:17.040 depends on how close they are to the original yawning individual. 0:08:17.720 --> 0:08:20.440 The yawns of friends and family members are much more 0:08:20.600 --> 0:08:24.560 likely to elicit a contagious yawning response, and the same 0:08:24.680 --> 0:08:28.000 seems to be true of humans. A few studies have 0:08:28.080 --> 0:08:32.000 tried to test this based on yon responses in autistic 0:08:32.200 --> 0:08:36.080 versus allistic children and adults, working off the concept that 0:08:36.160 --> 0:08:42.000 these groups process facial cues and empathetic responses differently. Often 0:08:42.080 --> 0:08:44.680 these sorts of tests will show a subject video of 0:08:44.720 --> 0:08:48.680 someone moving their mouth versus actually yawning, and then measure 0:08:48.720 --> 0:08:53.920 the subject's response from there. But empathy in general and 0:08:54.040 --> 0:08:58.640 the autism spectrum, both relatedly and separately, are very complicated, 0:08:58.840 --> 0:09:01.640 and the results of these studies really only indicate that 0:09:01.720 --> 0:09:07.000 more research is necessary. A leading hypothesis these days has 0:09:07.040 --> 0:09:10.439 to do with yawning occurring around states of bodily change, 0:09:10.960 --> 0:09:15.360 like between sleeping and waking. It also ties back into 0:09:15.440 --> 0:09:19.319 yawning creating increased blood flow to the brain, which can 0:09:19.360 --> 0:09:23.559 help us be more alert. The concept goes that yawning 0:09:23.720 --> 0:09:29.400 is an involuntary response to stressful situations. Some Olympic athletes 0:09:29.440 --> 0:09:32.959 will yawn right before their event. Some dogs will yawn 0:09:33.000 --> 0:09:36.440 when they're anxious like at the vets office, or excited 0:09:36.640 --> 0:09:39.680 like when you come home. It's a way to sort 0:09:39.720 --> 0:09:44.760 of stretch and come into your body and focus, and 0:09:45.280 --> 0:09:49.640 evolutionarily seeing that happening to someone in your group and 0:09:49.880 --> 0:09:54.760 automatically getting in on it too sounds pretty worthwhile, even 0:09:54.760 --> 0:09:57.480 if a yawn just means that your compatriot is sleepy 0:09:57.520 --> 0:09:59.760 and trying to wake up, it'd be good for you 0:09:59.800 --> 0:10:04.800 to join in on the increased vigilance the aforementioned Andrew 0:10:04.840 --> 0:10:08.760 Gallup at a Sunny polytechnic recently ran a study where 0:10:08.920 --> 0:10:12.160 they showed subjects video of people yawning or just moving 0:10:12.160 --> 0:10:15.840 their mouths, and then showed them images that could include 0:10:15.880 --> 0:10:19.120 a threatening stimulus in the form of a snake or 0:10:19.240 --> 0:10:21.800 a non threatening stimulus in the form of a frog. 0:10:23.120 --> 0:10:26.040 The subjects were then asked to pick out the snakes 0:10:26.040 --> 0:10:30.120 and frogs and the images as quickly as possible. After 0:10:30.160 --> 0:10:34.559 watching people yawn, the study subjects became able to identify 0:10:34.679 --> 0:10:39.000 the snakes faster, and only the snakes. This had no 0:10:39.080 --> 0:10:43.800 effect on frog identification. So even though we still don't 0:10:43.880 --> 0:10:46.800 know for sure why we yawn, we do know lots 0:10:46.800 --> 0:10:50.840 of interesting things about it. By the way, there is 0:10:50.880 --> 0:10:54.040 such thing as excessive yawning. It can indicate that something 0:10:54.040 --> 0:10:57.960 in your system is off. Usually that's your sleep quality, 0:10:58.320 --> 0:11:01.840 but it can also be something more immediately serious, like 0:11:01.880 --> 0:11:05.800 a heart attack or stroke, or epilepsy or multiple sclerosis. 0:11:06.920 --> 0:11:10.560 So if you suddenly find yourself yawning a lot, especially 0:11:10.600 --> 0:11:13.480 if you have any other symptoms or changes that seem 0:11:13.480 --> 0:11:16.000 out of place, get in touch with the healthcare provider. 0:11:17.040 --> 0:11:19.760 It probably doesn't count, though, if the yawns you're noticing 0:11:19.760 --> 0:11:22.719 all happened while you were listening to this episode, though 0:11:22.840 --> 0:11:30.720 we hope it wasn't that many. Today's episode is based 0:11:30.720 --> 0:11:32.920 on the articles why do We Yawn? By Melanie red 0:11:33.000 --> 0:11:36.720 Zeki McManus and why is Yawning Contagious? By Josh Clark, 0:11:36.880 --> 0:11:40.000 both on how stuffworks dot Com. Brain Stuff is production 0:11:40.040 --> 0:11:42.720 of iHeartRadio in partnership with how stuffworks dot Com and 0:11:42.800 --> 0:11:45.760 is produced by Tyler Klang. For more podcasts from my 0:11:45.800 --> 0:11:49.680 heart Radio, visit the Aheartradio app, Apple Podcasts, or wherever 0:11:49.720 --> 0:11:51.280 you listen to your favorite shows.