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Studies on the physical and wning The act of yawning has been observed in all vertebrates, and occurs in humans as early as minutes after birth, so it must have some definitive physiological purpose. Until recently, most scientists believed yawning was a respirat ....

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.... yawning. They predicted that signs of arousal would increase when the yawn started. A mixed-gender group of 30 college students participated in three 15-minute laboratory trials which measured skin conductance and heart rate, two physical correlates of arousal. In each trial, subjects pressed a button when they felt a yawn coming on, and equipment in a nearby room took readings from sensors attached to their fingertips. The first trial measured skin conductance, the second trial measured heart rate, and the third trial used an electromyogram with electrodes attached to the subjects’ masseter muscles to verify that they were yawning when they ....