BioQuakes

AP Biology class blog for discussing current research in Biology

Tag: yawning

Yawning: Why is it Contagious?

Have you ever wondered why we yawn even if you’re not tired, or if someone else yawns? The University of Nottingham published an article called “A Neural Basis for Contagious Yawning” in Current Biology. This study was led by Stephen Jackson, a professor of Cognitive Neuroscience at the University.  The research group worked to find reasons as of why yawning is contagious.

The group concluded that yawning is a form of echophenomena. An echophenomenon is an automatic action without awareness. It is a result of external stimuli. Yawning is an echophenomena because people yawn when they see other people yawn.

This study did not find the neural basis for yawning, but used tests to try and figure out what the neural basis is. The team used transcranial magnetic stimulation (TMS) on 36 adults to test for the neutral basis. TMS is a procedure that uses magnetic fields to activate nerves in the brain. The stimulation increases the need to yawn. The adults were shown videos of people yawning and were told to yawn when needed or to resist the yawn. The number and the intensity of the yawns was recorded. Georgina Jackson, a professor of cognitive neuropsychology in the Institute of Mental Health, quoted that “this research has shown that the ‘urge’ is increased by trying to stop yourself. Using electrical stimulation we were able to increase excitability and in doing so increase the propensity for contagious yawning.” This method can me used to figure out when contagious yawning will occur.

Yawning is a natural human function that happens daily. It is interesting to learn about how it works and how one’s yawn can affect other people. Although there is not yet a clear answer of how this works, it is fascinating to learn about different theories from different researchers. For more information on contagious yawning click here and here. Based on reading this research, what do you think the best explanation to contagious yawning is?

 

 

 

 

 

Yawning and Brain Size

macaca_fuscata_juvenile_yawning

Recently, scientists discovered a correlation between yawning and brains: the longer the average duration of a specie’s yawn, the bigger that specie’s brain size,  as measured by brain weight and total number of cortical neurons.

The study was conducted on 109 individuals from across 19 different species, including cats, humans, mice, camels, and more. The investigators found that the duration of yawns was shortest in mice, who averaged 0.8 seconds, and longest in humans, who averaged 6.5 seconds. The scientists plan on investigating whether this correlation holds true amongst individual members of a species.

The study was created in response to the ideas set forth in Gallup’s 2007 paper on the thermoregulatory theory of yawning, one of the strongest theories about why we yawn (we do not yet definitively know the biological purpose of yawning). The thermoregulatory theory indicates that yawning cools down the brain in homeotherms via three potential mechanisms. But whether or not this brain-cooling is simply a side effect or the primary function of yawning is up for debate.

Based on Gallup’s paper, the investigators of this study hypothesized that longer yawns would produce greater physiological responses, in terms of blood flow and circulation to the brain– which would be evolutionarily necessary for species with larger, more complex brains.

There are other theories about why we yawn, such as a 2014 paper stating that yawning stimulates cerebrospinal fluid circulation, which in turn increases species’ alertness. A common theory that yawning increases blood oxygen levels has largely been disproved. How would such alternate theories have different implications for the discovered correlation between yawning and brain size?

Drowsy Dogs

Flickr
Photo By: recompose

When a person sees another person yawning, they are more prone to yawn as well. As it turns out, so are puppies. According to a new study, puppies are susceptible to human yawns as well!

Elaine Alenkær Madsen, PhD, and Tomas Persson, PhD, researchers at Lund University, have been studying the yawn contagion, specifically between different species. They were able to determine that puppies above the age of seven months were susceptible to yawning when a human yawned. But, they also found that the puppies under the age of seven months did not yawn when the humans in the experiment yawned.

These findings are similar to those found for human beings. Children only begin to become susceptible to yawning at around the age of four. These results help to prove that there is a general developmental pattern, concerning empathy, that is shared by humans and other animals. These results could help other researchers in discovering more about the developmental processes of human beings and other animals similar to them, like monkeys, apes and now dogs.

 

For mor information on this subject please check out:

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0028472

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