The first "belly laugh" I ever heard came from my healthy breastfed son while he watched his older brother, age 5, sail past him again and again with a home-made sheet-cape flapping behind him like Superman. No entertainer ever had a happier audience. The second "belly laugh" I ever heard from him was when I fell asleep while he was nursing. He took my breast from his mouth and squirted me in the face. My startled awakening was highly appreciated by his keen sense of humor! He was just a few months old and I took this as a sign of high intelligence. He is now a 25 year old engineer, highly intelligent and still has a great sense of humor and playfulness about him. That's what happens when you nurse your babies for 3 years or longer.