my baby is 4 lonths and 3 weeks old, but not laughing a loud. He smiles at looking mother and father but laughing a loud what should I do

A. That’s okay a lot of kids don’t laugh in this age most of the kids would smile only and there’s nothing wrong with it and hardly one or two kids maybe you will see who made laugh but most of the kids actually smile only and that is natural for them don’t worry