03/27/2009 05:12 am ET | Updated Nov 17, 2011

Goosebumps, Freckles, and Cracking Joints: 13 Body Quirks Explained

The truth behind 13 physical quirks--plus easy ways to feel better.

1. Why Do You "Laugh Until You Cry"?
Experts don't really know. One thing to consider: Laughing and crying are similar psychological reactions. "Both occur during states of high emotional arousal, involve lingering effects, and don't cleanly turn on and off," says Robert R. Provine, PhD, a psychologist at the University of Maryland, Baltimore County, and author of Laughter: A Scientific Investigation. We associate crying with sadness, but tearing up is an even more complex human response. Tears are triggered by a variety of emotions--"by pain, sadness, and in some cases even extreme mirth. It's just the way we've evolved," says Lee Duffner, MD, a professor of ophthalmology at the University of Miami's Bascom Palmer Eye Institute.

As it turns out, that's good, because both laughter and crying can ease a stressful experience, probably by counteracting the effects of cortisol and adrenaline. So if you ever find yourself laughing until you cry, count yourself lucky.

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