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Developmental psychologists are split over this question. Some claim that babies are born with the ability to feel and express four basic emotions -- including happiness -- and others argue that infants learn to identify and communicate different feelings only through experiences with other humans. But they all agree that your newborn doesn't get the punch line of your hilarious jokes. Is she even aware that she finds something you said or did funny? Probably not. But that doesn't make her giggles any less precious. When a baby laughs, it's a positive thing -- she's enjoying herself. Your baby's first laugh, which typically trills out before she's 4 months, is a sign of socialization. She's picking up on the sounds and expressions you make when the two of you are having fun. --Hagar Scher
Originally published in Parents magazine, October 2006. Updated 2009
The answers from our experts are for educational purposes only. Please always refer to your child's pediatrician and mental health expert for more in-depth advice.