The world is bad, but babies remain good. Babies are especially good when they are laughing, which they start to do at around three and a half months old. Babies laugh when other people do things, like tickle them or play peek-a-boo, or when other people are laughing. That’s because babies are much cuter than adults, but it’s also because, unlike adults, babies laugh both on the inhale and on the exhale, as described by new research presented at the Acoustical Society of America’s 176th Meeting.