 [ Symptoms ] why do we yawn [ Disease ] is a yawn always linked to exhaustion fatigue or the need for sleep actually no yawing can be connected to any number of conditions and even emotions including stress boredom lack of stimulation which can be code for boredom and being overworked another code for tiredness i have no idea why yawning can be so “contagious” — watching someone yawn or for that matter just hearing someone yawn or even thinking of yawning can trigger you to yawn as well  strangely we do not actually know why we yawn just as sleep remains much a mystery so does this universal human behavior and actually most animals yawn a single yawning shark can set off a yawn reaction in the entire school a few theories exist though to explain human yawning do increased amounts of carbon dioxide in the blood induce yawning to bring in oxygen this theory has been around since hippocrates but studies have since shown it to be either incorrect or flawed why because yawning may in fact reduce oxygen intake compared to normal respiration breathing not increase it is yawning the body is way of controlling brain temperature this theory suggests that yawning cools off the brain much like a fan cools the insides of a computer reptiles for instance might yawn to maintain their body temperature since most reptiles rely on ambient temperature to maintain body temperature yawning might be a means for promoting rapid cooling down this may also work for animals that do not sweat pigs and dogs may yawn because they do not sweat exposing the mouth and tonsils to the outside air may cool down the head even if only by a few tenths of a degree does yawning satisfy the need to stretch your muscles is a yawn associated with nervousness do yawns help you to stay alert some studies have suggested that yawning — especially “contagious” yawning — may have developed as a way of keeping a group of animals alert anecdotal evidence suggests that yawning helps increase the state of alertness of a person paratroopers for instance have been noted to yawn in the moments before they exit the aircraft is yawning a sign of dominance observation of dog and primate behavior has shown that alpha males and alpha females tend to yawn more frequently than do their beta counterparts yawning may actually be considered aggressive in certain species since it is a chance to display lots of pointy teeth none of these theories has been definitely proven and these are just the tip of the theoretical iceberg though some scientists are now claiming that yawning is a sign of sexual attraction rather than a desire to sleep i am not so sure we may never know exactly why we yawn or why dogs monkeys and all other vertebrates — with the inexplicable exception of the giraffe — do it either perhaps giraffes do yawn and we just have not or can not  observe it and perhaps