In Italy, it's called il gioco di cucù.
Palestinians say bah einu, and in Japan, it's inai inai ba.
But in every language, the response is usually the same.
Peekaboo is a near-universal source of laughter and connection for infants and adults.
It's the first game that almost everyone plays.
So what is it about this goofy game that babies love so much?
While infants develop at different rates, many cognitive and motor abilities emerge in a certain order.
For example, while six-month-olds can typically grab things and then promptly drop them, walking and talking generally begin around 12 months.
This timeline was first formally charted in 1936 by Swiss psychologist Jean Piaget.
And while most modern researchers agree this process is more fluid than Piaget believed, the early developments he identified are key for understanding peekaboo.
