15 months old
The joke Your toddler is tickling you.
Why it's giggle-worthy This time, she's making you laugh. "Babies seize on figuring out what people find funny," says Vasu Reddy, Ph.D., a professor of psychology at the University of Portsmouth, in England. "By the end of the first year, most kids are doing something to elicit laughter." You may have noticed this around 7 or 8 months, when Baby made a silly face over and over because it cracked Dad up. But by 15 months, some tots are really starting to work the room, and a tickle attack on Mom has the added fun of being a zany role reversal. "My girls went through a phase when they thought it was hysterical to 'feed' Mommy," says Crystal Willis, a mom of four from Silver Spring, Maryland. "They would put a Cheerio in my mouth and laugh and laugh."