无聊的理论：第三、最常见的假设背后打哈欠是无聊，即一个人或动物会在无聊或感到嗜睡（Leone et al，2014）。这是一个被广泛接受的理论打哈欠而无法解释，为什么一个运动员打哈欠准备运动之前攻击别人或即使是一只狗打哈欠之前的原因，因为在这两个情况有没有空间，而不是那些无聊的兴奋和警觉的时刻。
大脑冷却理论：在各种实验的帮助下，研究人员发现，当人们想保持头脑冷静的时候，人们往往会打哈欠，当他们的大脑被温暖的时候，人们会打哈欠。一个冷静的大脑工作在更好的方式，因此打哈欠有助于使大脑平静下来，在紧张或焦虑的时刻放松。打哈欠象征着从身体所有负面能量的外向，因此有助于使身体更轻松活跃（Leone et al，2014）。
Boredom Theory: The third and the most common hypothesis behind yawning is boredom, i.e. a person or even animals yawn when they are bored or feel lethargy (Leone et al, 2014).This is a widely accepted theory about yawning but it fails to explain the reason that why an athlete yawns before going for the sport or even a dog yawns before attacking on someone, because in both the situation there is no space for boredom instead those are the moments of excitement and alertness.
Brain Cooling Theory: With the help of various experiments, the researchers have found that people tend to yawn when they want to keep their brains cool i.e. people yawn when their brains are warm. A cool brain works in better way and hence yawning helps to make the brain calm down and relax in a moment of tension or anxiety. Yawning symbolically represents the outgoing of all the negative energy from the body and hence helps in making the body more relaxed and active (Leone et al, 2014).
From many of the studies and the evidences yawning proved to be a major facilitator of behavioral stimulation. The most significant role of yawning is to maintain or increase stimuli even when a small stimulation is provided by environment. Sometimes a small or insignificant stimuli produced by environment could go unnoticed. Yawning helps to increase them. There are numbers of functions of yawning but the most important and significant one is to regulate the arousal. This means that after a person yawns in a boring environment, his alertness increases and drowsiness decreases (Massen et al, 2014). There are various variables, like heart rate, electroencephalogram etc. which help in measuring the alertness. As mentioned earlier, yawning helps in pumping more oxygen to the brain which makes the brain to function in a more appropriate manner.