9 months old
The joke Mom is wearing a shoe as a hat.
Why it's giggle-worthy It's absurd. Your tot needs to perform some impressive mental gymnastics to comprehend this. She first has to know that shoes go on feet, not heads, a fact she's picked up in the past few months by watching the people around her. By 9 months, children can sense when something is ridiculous, so they love when they notice strange happenings. "When my son, Boyce, was a baby, his older sister, Naomi, walked into the room and, without a word, put a paper bag over her head," says Laura Rawlins, of Ames, Iowa. "Boyce began to laugh so hard he couldn't catch his breath. Naomi removed the bag, said hello, then put the bag back on her head, and the hoots started again." In true tot fashion, anything that's funny once is funny five times in a row. "Parents forget this because it's so simple, but if there's something that makes your baby laugh, repeat it," says Lawrence J. Cohen, Ph.D., author of Playful Parenting. "We adults tend to get bored, but for a baby, everything is so new that it might still be funny 20 or 30 times."