Peek-a-boo!

Somewhere between the 2nd and 3rd month of life, Cyrus started blabbering and using his voice to express a wide range of emotions. His first word wasn't mama or papa but Earl (highly disputed by my wife who claims he was saying uggh instead. I beg to differ...). The one event that made us drop everything and stare at him was when we realized he was laughing. Oh yes he'd smile before this, and try to laugh, but always without the accompanying audio.

Why are babies amused by peek-a-boo? And we tried peek-a-boo-ing with two people hiding behind the blanket instead but he wasn't amused at all. Then we returned to just one peek-a-boo-er and he resumed laughing like normal. Remind me to check the rules regarding multiple peek-a-boo-ers/peek-a-boo-ees.