Few things are as heartwarming as hearing a baby's first laugh. I’ve experienced that moment with four children of my own, ...

Humor has always been subjective. Where some people prefer the physical comedy of Jim Carrey, others may find the dry approach of Albert Brooks preferable. Babies, of course, are not big on subtlety.

Dr. Mireault is a developmental psychologist at Vermont State University. My son was 14 weeks old when he made his first unmistakable whole-body belly laugh. In the months that followed, his laughter ...