In Time magazine, Jeffrey Kluger pointed out how newborn babies display the need for affection we all feel.

Of all the urges that drive us, it's the passion to be held that makes itself known first. If a baby is startled fresh from the womb, German pediatrician Ernst Moro discovered in 1918, its arms will fly up and out, then come together in a desperate clutch.

Holding is good, and floating free is bad—a lesson that's not so much learned after birth as preloaded at the factory. In fact, doctors have long known that babies who aren't held simply fail to thrive.

Not surprisingly, it's a need we never outgrow. In one way or another, we spend the rest of our lives in a sort of sustained Moro clinch.