We all share certain reflex behaviors in common that to this day remain little understood by science. Take yawning, for example. A yawn, we know, is a sign of boredom. But a yawn can also be triggered by sleepiness or hunger. It can be brought on by anxiety and stress. Concert violinists often yawn as they get ready to go on stage to play a concerto. So do Olympians before a race, or paratroopers getting ready to do their first jump. Some recent research has also concluded that the purpose of yawning is to cool the brain.
We now know these things thanks to a dedicated form of study that's been with us since the early 1980s known as "yawn science." And, as I write this, researchers continue to busily engage in debate on the significance and origins of yawns. While they all appear to agree on what can trigger a spontaneous yawn, it seems none can yet tell us exactly what a yawn accomplishes. One line of thinking is that the yawn is designed to perk us up by increasing heart rate, blood pressure and respiratory function.
"[Yawning] stirs up our physiology and it plays an important role in shifting from one state to another," Robert Provine, professor of psychology and neuroscience at the University of Maryland, Baltimore County recently told NPR. Not all researchers agree with this line of thinking.
It is also believed that contagious yawning evolved to boost social bonding. This social bonding theory is supported by a 2011 study that found people are more likely to copy a yawn if they know the person who is yawning as opposed to that of a stranger. Just the sight of a yawn or even hearing a yawn, thinking about yawns, or talking about yawns can trigger a contagious yawn response. For all I know, you may be yawning right now.
Yawning is also a common behavior in animals. It is widespread across the animal kingdom, yet very few animals yawn contagiously. Contagious yawning — the kind that's an indicator of community and kinship — has only been found in humans and a handful of animals. Chimpanzee groups share collective yawns. So does your family dog.
"Our results show that the emotional bond between people and their dogs is reciprocal," Teresa Romero, an animal behavior researcher at the University of Tokyo told NBC News. A shared yawn with a pooch can be a sign of emotional connection, or empathy between you and your pet. When you yawn, they may do so as well.
Sneezing is another reflex action that is the subject of ongoing scientific research. That sneezing is a natural response to a cold or irritants infiltrating the nose lining is easy to understand. It's the body's way of expelling the foreign matter and protecting the lungs and other organs from contamination; from things such as germs, dust, pollen, animal dander, or pollutants.
Yet some people, not everyone, will also sneeze in response to cold air or bright sunlight. One in four people are said to sneeze in bright sunlight. What's that all about?
In answer to the question of why we sneeze, researchers from the University of Pennsylvania in Philadelphia recently have come to believe that it's similar to the body rebooting, much like a computer does. We need to reset our nasal environment every once in a while, they believe, and sneezing is how we do it. Various things seem to trigger this reaction.
Rarely does the act of sneezing involve only one sneeze. What's observed is that it generally happens in groups of two or three done in quick succession. As we've all observed, sneezes come in all sorts of shapes, sizes and in volume and sound. We also know that the sneeze reflex triggers a contraction of muscles throughout the body. Why this occurs remains a mystery.
The number of sneezes in a series by any individual is believed to most likely come from a personal tic based on differences in anatomy and self-control. The supposed record for the longest continuous sneeze is said to belong to a young woman in Worcestershire, England — a total of 978 days. No word seems to be available on what caused her to sneeze in the first place or why she finally stopped. It must also be noted that typically people don't sneeze when they are sleeping. In sleep, the nerves involved in sneezing are relaxed, breaking the chain reaction of the sneeze, though an irritant could cause someone to wake up and sneeze.
The habit of a person "cracking" their knuckles may not rise to the level of a universal reflex behavior, but studies show that it is practiced by as many as 45 percent of people.
According to Dr. Pedro Beredjiklian, chief of hand and wrist surgery at Philadelphia's Rothman Institute, when a person pulls, twists or otherwise "cracks" a joint, they are, in effect, expanding the volume of space between their bones. As he recently explained to TIME magazine, this expansion creates negative pressure that sucks fluid (sort of the body's motor oil) into the newly created space creating the popping a person feels and hears when they crack a knuckle.
Is this bad for your joints? Contrary to popular opinion, Dr. Beredjiklian does not believe so. Multiple studies have found no evidence that finger pullers and poppers are more likely to suffer from arthritis, for example, than those who don't crack their knuckles. A recent study found also that people who cracked their knuckles had the same levels of swelling, weakness, ligament looseness and physical function as those who did not. At least one study concluded that knuckle cracking offers those who do it an almost therapeutic benefit.
Write to Chuck Norris ([email protected]) with your questions about health and fitness. Follow Chuck Norris through his official social media sites, on Twitter @chucknorris and Facebook's "Official Chuck Norris Page." He blogs at http://chucknorrisnews.blogspot.com. To find out more about Chuck Norris and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate Web page at www.creators.com.