In Italy, it’s called il gioco del cucù. Palestinians say ba' 'éno. And in Japan, it’s inaīnaibā! Peek-a-boo 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? Dig into how this simple game promotes the development of our cognitive, motor, and social skills.