Comment by jlhawn

The main idea behind the popular book _The Happiest Baby on the Block_ is that true cause of colic (inconsolable crying by newborns) is "The Missing Fourth Trimester". During the first 3-4 months after full term, the best methods for soothing an infant are recreating the conditions it experienced in the uterus. Humans evolved to "evict" their babies earlier due to the species' growing head sizes necessary for larger brains. After the infant's first 100 days, they are better able to self-sooth and can explore their environment (with help and supervision) to best continue brain development.