What causes them?

Yawns-

If your body is low on oxygen, your mouth opens wide and tries to suck more in. Yawning is a way to regulate the amount of carbon dioxide and oxygen in your blood. Unfortunately, yawns are nearly impossible to stifle.

Hiccups-

If you’ve frequently got a case of the hiccups, try slowing down when you eat and drink, suggests Dr. Plasker. Doing either too quickly causes your stomach to swell; this irritates your diaphragm, which contracts and causes hiccups. You may also get hiccups in emotional situations or if your body experiences a sudden temperature change. In both of these cases, the hiccups are a result of a glitch in your nerve pathways, which is why a sudden scare—which might shake up and reset your nerves—can sometimes end an episode.

Goose Bumps-

Those tiny bumps that cover your skin when you’re cold or scared are actually a defense mechanism. Goose bumps occur when the arrector pili, a tiny muscle that connects the hair follicle with skin, contracts and makes the hair stand on end. If you had more hair—like cavemen did—the upright hair would trap air to keep you warm or make you look bushier and therefore more threatening to predators.

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