By 6 months of age, a baby typically can experience surprise, disgust, happiness, sadness, anger, and fear. What babies don’t have are a lot of filters. Crying for many months remains the shortest, most efficient means of getting a parent to put a Post-it note on them. Parental attention is deep in the survival interests of the otherwise helpless infant, so babies cry when they are frightened, hungry, startled, overstimulated, lonely, or none of the above. That makes for a lot of crying.
