A baby’s smile is a dancing flower of twinkling stars. The whole universe dances with joy when a baby smiles… ?VIDEO

Somewhere between that first smile and the first recognizable syllable, the magical sound of a child’s first laughter arises. It could be a reaction to belly kisses, toe tickling, or brisk riding on daddy’s knee. Triggers are different, but laughter is inevitable.

“In all cultures, it begins to develop in infants between 3 and 4 months of age,” says Robert R. Provine, Ph.D., professor of psychology at the University of Maryland, Baltimore County, and author of Laughter: A Scientific Study. However, don’t worry if you haven’t heard laughter after 4 months. “As with all milestones, some babies may laugh a little later,” says Sheila Gahagan, MD, professor of clinical pediatrics at the University of Michigan C.S. Mott Children’s Hospital.

Although children start laughing early, it takes a long time before they appreciate a good joke. Meanwhile, what can tickle their funny bones? “Toddlers tend to find auditory and tactile sensations fun,” says Dr. Gahagan. “Funny lip-clapping sounds, whispers, raspy voices, gentle puffs on hair, or kisses on the belly.”