What Causes Hiccups? And More Tricky Kid Questions

Do you feel like a fraud when your kids ask why the grass is green? (Because it contains chlorophyll—ring a bell?—a green pigment plants use to make their food.) Behold this parental compendium of uncommon knowledge, which explains a few mysteries of the universe.

What Causes Hiccups?

Hiccups usually occur when the stomach rubs against and irritates the diaphragm, a muscle at the bottom of the rib cage. An irritated diaphragm pulls back fast, forcing air sharply into the lungs, says Norman H. Edelman, M.D., the chief medical officer for the American Lung Association. When the air hits your voice box, you hiccup. This happens repeatedly until the irritation stops.

Why is Yawning Contagious?

Two Italian scientists studied this puzzling phenomenon just last year: They believe that contagious yawning shows empathy. (When you yawn after your mom does, maybe you’re saying, “I hear you. I’m sleepy, too.”) In fact, we’re more likely to “catch” a yawn from a close friend or a family member than from an acquaintance or a stranger.