Why do we laugh? And other impossible questions


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Your body is an amazing machine, and it evolved over the generations to do some pretty incredible things. But are you always in control? What about those times when the body does exactly what it wants without asking you first? We decided to take a look at those involuntary signals your body sends out and what lies behind them.


Why do we hiccup?

Let's face it: hiccups are just plain irritating. They make us feel pretty silly and nobody quite knows how to make them stop. But why do they happen in the first place? Hiccups are caused by a spasm in the diaphragm — the muscle between the chest and the abdomen. Possible reasons for this spasm can be anything from eating food too quickly to a rapid change in body temperature to emotional stress or shock.

According to Medical News Today, when the stomach becomes distended, it irritates the diaphragm, causing it to contract. This results in a sharp intake of air which is suddenly stopped by the closure of the vocal folds (sometimes erroneously called vocal cords). This stoppage causes the familiar "hic."

Like the blush, we don't quite know why evolution gave us the hiccup. Some suggest it's a safety measure that allowed us to clear blockages when we ate on all fours, others that it originates from much earlier in the evolution process.

Scientists have observed that tadpoles have a hiccup-like way of breathing midway through their development from gills to lungs. They take in oxygen-rich water through the mouth, close the vocal folds and expel it through the gills. See? It's not an embarrassing social problem — it's a family tradition.


Why do we yawn?

We yawn when we're bored or tired, when our brains are feeling fuzzy and we feel like switching off — that Friday afternoon feeling. Because of this, it was once thought that the extra intake of air was the body's way of increasing the amount of oxygen in the blood — a little kick-start to keep you conscious, perhaps?

Recent research at the University of Vienna, however, has put forward a more convincing argument. The scientists discovered that there is no significant increase in oxygen in the blood following a yawn. They also discovered, however, that increases in brain temperature corresponded with outbreaks of yawning. Fatigue and lack of sleep are both known to increase brain temperature. The brain needs to maintain a comfortable environment just like any computer and the study appears to indicate that the involuntary intake of air is intended to cool it down. They also found that people yawn less in winter than in summer.

Aside from so-called 'spontaneous' yawning by an individual, 'contagious' yawning among groups of people can also be explained by the theory. Humans existing in interdependent societies send messages via the yawn encouraging each other to compensate for any overheating, tiredness or lethargy that might be experienced by the group. So, the next time you're mouth is gaping on the bus home, just remember: you're not being rude, you're helping others.


Why do we blush?

Ever felt more embarrassed by your blushes than by the fumble that caused them? Why do we advertise our discomfort? Unfortunately, the reason for blushing is not fully understood but we all know that it is an involuntary response to stress of some kind. Some argue that evolutionarily it serves as a social regulator. It is a signal that lets others know that we are stressed, ashamed or flustered.

By blushing we visibly demonstrate to others that we are uncomfortable in certain social situations and so tell them that we understand and are affected by the rules of our group. This means we are perceived to be less of a threat to those around us. When we commit a faux pas, we immediately "say sorry" with a blush. Alternately, when we blush at others' activity, we are unmistakably sending them the signal that we "disapprove" of the way in which they are acting against the interests of the group. Maybe you don't feel so silly now.


Why do we blink?

We blink our eyes around 15-20 times a minute and each one lasts about a tenth of a second. That means, with blinking alone, you have your eyes closed for about 42 minutes for the two thirds of the day you're awake. The reason we don't notice all this darkness is because of a clever trick the brain has developed — it momentarily shuts down those sections of our processing that recognize changes in visual stimuli; effectively your brain "ignores" the blink and your brain enjoys a continuous, uninterrupted view.

The immediate purpose of blinking is simple. Each time you blink, the eyelid "washes" the surface — or cornea — with fluid from the tear ducts at the corner of the eye. This stops the eye from drying out and clears away any debris, dust, skin cells and so on that may have collected there. Yet we seem to blink more frequently than would be necessary for this alone. Research by a team at Osaka University in Japan suggests that each blink actually provides a minute break from the world. The team found that blinking in subjects corresponded with a burst of activity in the "default network," the part of the brain that functions when it is in "wakeful rest" rather than being stimulated by input from the outside world.

This makes sense when you consider the observations that show that, far from blinking randomly, the pattern is somewhat predictable. People reading tend to blink at the end of sentences and people listening to speech blink during pauses. Perhaps the interjection of wakeful rest is part of the process of digesting information, allowing us to "clear the palate" before the next course.


Why do we laugh?

Laughter is no joke. In fact, humans may well have developed laughter as an important cohesive social function. Robert R. Provine of the University of Maryland suggests that we laugh "30 times as much when we're with other people than we do when we're alone." Groups of people communicate with each other with laughter to strengthen social bonds: when we we're laughing together, we're mutually safe.

This is significant not only because of the chemicals the individual body releases when it is happy but also because of the security we feel when we identify with those around us. Like blushing, laughing is spontaneous and (almost) uncontrollable. The element of honesty in laughter provides us with a direct insight into the thoughts and moral character of others meaning (we feel, at least) we can make an honest assessment of them.

Laughter, says Provine, first occurs around three and a half to four months of age. Furthermore, it develops in people who are blind and deaf, which means it's instinctive rather than learned behavior. Ultimately, it is believed that human laughter grew from the panting that primates exhibit when involved in playing, chasing or friendly wrestling — activities that are certainly comparative to those that might produce human laughter. After all, as Norman Cousins said, "hearty laughter is a good way to jog internally without having to go outdoors." At this time of year, that certainly sounds like a plan.