Developmental Timetables

New parents worldwide are delighted on a daily basis by their young infant’s accomplishments. From the parents’ perspective, one day their infant is unable to crawl, does not reach for nearby objects, does not necessarily smile at them or produce words, and then the next day these abilities appear as if from nowhere. Such developmental milestones—the emergence of a key skill or ability—are viewed as important by parents, educators, and psychologists because infants reach them universally around the same age, and they are considered evidence of healthy, typical development. Moreover, because these abilities emerge in a consistent order or developmental timetable that begins at conception and continues into late adulthood—with infants, for example, able to crawl before they can walk and babble before they can ...