Even though crying is still your baby's strongest form of communication, he's also developing his sense of humor during his fifth month. He may start to laugh at pleasant surprises such as your face appearing from underneath a blanket or a toy popping out of a box, provided it isn't too loud or startling. Encourage your baby's laughs, giggles, and smiles with funny faces and lots of general silliness. Babies enjoy hearing a variety of sounds and you don't need special toys or instruments to provide them. Simply click your tongue, whistle, or make animal noises your baby will love it.