My daughter, Alice, is almost two, and quite funny. Although she can say short sentences—“I need cake!”—her humor isn’t particularly verbal. Instead, she giggles while stumbling around in grownup shoes, or blows bubbles in her water when she should be drinking it. She likes to put on a hat, pull it down over her eyes, and then blunder around, arms outstretched, like a mummy. She’s also discovered the humor of exaggeration: recently, when her brother resisted getting out of his pajamas in the morning, she sidled up, grabbed his shirt, hauled on it with both hands, and laughed while yelling, “Ooooouuuut!”

The Early Humor Survey , a roadmap to the emergence of little-kid humor between the first and forty-seventh months, took a team of psychologists about a decade to develop. According to t

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