Alert for uncles, aunts and grandparents: If there is a five-year-old in your life, learn some knock-knock jokes.
Parents will no doubt have already noticed that a good knock-knock jokes can cause a five-year-old to collapse in giggles. But occasional visitors can score big with a good repertoire of knock-knocks, puns, and simple jokes.
According to a 2012 study, humor lights up the same parts of the brain in both adults and children. The adult humor centers are more developed, of course, but at age five, kids begin to understand the sequence of a story (start, middle, and end) and a joke. Knock-knocks are perfect for their new discovery, but they also respond to slapstick, exaggeration, and puns.
In fact, kids start working on the humor centers pretty early — as soon as they respond to peek-a-boo. A developed sense of humor has been linked to creativity, empathy, and resiliency, according to The Globe and Mail.
But if you want to appeal to a five year old, learn some good knock-knocks like these:

Knock, knock.
Who’s there?
Tank who?
You’re welcome.

Knock, knock.
Who’s there?
Howl who?
Howl you know unless you open the door?

Knock, knock.
Who’s there?
Boo who?
Don’t cry, it’s just a joke!